User’s Guide Portable Radiation Package, Model 2 (PRP2) October 3, 2011 the fast-rotating shadowband radiometer (FRSR) SYSTEM ARCHITECTURE What is the basic PRP block diagram? Interface to the AMF2 guest sensor module. Where is the part list? What are the assigned IP addresses? About the hardware: What is the PRP? CDU? RSR? TCM? GPS? RAD? DAQ? What is the ethernet hub, a.k.a. the PDS752? 18 How do I change the hub IP? 42 Shipping and Unpacking: Packing list. How do I unpack the system? Choosing a deployment location? How do I put it all together? Connecting the pieces. How about grounding? Check the power system? Is a preliminary test required? When the system is running how do I: read latitude and longitude? read sog and cog? read magnetic variation? read short wave and longwave radiation? read PIR case and dome temperatures? read pitch, rol and headingl? read head temp? read ambient temp? read MFR head temperature? read pitch & roll? About the Rotating Shadowband Radiometer. 19 What is the TT8? 19 What does the TT8 software do? 19 How do I talk directly to the TT8? ?? Change EEPROM variables? ?? Read the MFR Head input voltages? ?? Read the MFR head temperature? ??
Transcript
User’s GuidePortable Radiation Package, Model 2 (PRP2)
October 3, 2011
the fast-rotating shadowband radiometer (FRSR)
SYSTEM ARCHITECTUREWhat is the basic PRP block diagram?Interface to the AMF2 guest sensor module.Where is the part list?What are the assigned IP addresses?About the hardware:What is the PRP?CDU? RSR? TCM? GPS? RAD? DAQ?What is the ethernet hub, a.k.a. the PDS752? 18How do I change the hub IP? 42
Shipping and Unpacking:Packing list.How do I unpack the system?Choosing a deployment location?How do I put it all together?Connecting the pieces.How about grounding?Check the power system?Is a preliminary test required?
When the system is running how do I:read latitude and longitude?read sog and cog?read magnetic variation?read short wave and longwave radiation?read PIR case and dome temperatures?read pitch, rol and headingl?
read head temp?read ambient temp?read MFR head temperature?read pitch & roll?
About the Rotating Shadowband Radiometer. 19 What is theTT8? 19What does the TT8 software do? 19How do I talk directly to the TT8? ??Change EEPROM variables? ??Read the MFR Head input voltages? ??Read the MFR head temperature? ??
The Portable Radiation Package (PRP) was developed to provide basic radiation information inlocations such as ships at sea where proper exposure is remote and difficult, the platform is inmotion and azimuth alignment is not fixed. Three radiation sensors are combined into a singlecompact package. (See http://www.rmrco.com/prod/prp2/index.html). An Eppley PSP and PIRprovide the global broadband downwelling shortwave and longwave irradiance. The microvoltanalog signals from these radiometers are sampled and converted to digital averages in physicalunits by the Radiation Analog to digital Interface (RAD). A novel Fast-rotating ShadowbandRadiometer (FRSR) operates on the same principle as the MFRSR without the need for preciseleveling and azimuthal alignment. Using an MFR head, direct beam radiance, diffuse and globalirradiance, and aerosol optical depth (AOD) are estimated for six 10 nm shortwave bands (415,500, 615, 680, 870, and 940 nm). The PRP is ethernet based and can be deployed in exposedlocations such as the ship mast or open deck areas.
Figure 1: PRP2 system under test. From left to right are the RSR (comprised of the Tilt-compass(TCM) sensor, Shadowband system, MFR head, and the cable connecting the head to the CDUbox), the PSP & PIR hemispheric radiometers and Radiatiometer Analog to digital interface(RAD), the Control Data Unit (CDU) and the small +15 VDC DC power supply.
Figure 2: Components of solar irradiance. The integrated downwelling radiation, global irradiance,can be broken into two components, the direct beam irradiance, those photons arriving from thesun without interraction with atmospheric molecules, and the diffuse irradiance which come frominteraction of the solar photons with molecules in the atmosphere.
The FRSR measurements allow one to separate the direct beam and diffuse irradiance.
Figure 3: Shadowband cycle. Figure 4: Dip in the solar signal.
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1.3 Functional block diagram
prp2systemblock100321
FRSR CDU
HUB
RADAnalog-digital
computer
FRSRFast-rotating
Shadowband radi-ometer
TCMPitch, roll &
FG compass
GPSLat, Lon,
SOG, COG, VAR
WXTWeather Station
winds, air temp, RH,baro, rain
PSP PIR
+12-18 vdcEthernet
Figure 5: PRP2 system block diagram. The PRP2 design has several independent componentsall networked through a central ethernet hub. The RAD, FRSR, GPS and TCM units use RS232serial lines. All serial lines come to a central ethernet hub that connects to the data acquisitioncomputer (DAC).
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1.4 The AMF2 Sensor Module
The AMF2 uses several “sensor modules” as a flexible interface between sensors and the datasystem. Because the PRP is not a standard ARM sensor, its module is called the “guest sensormodule.” Generally, on land, it is possible to deploy the PRP on the module as shown in figure 6.On a ship the deployment will be more challenging.
The module is powered by 120 VAC. It provides an air conditioned, dry environment. Data con-nection to the module is by Wifi. Inside the module an ethernet switch allows ethernet connectiondirectly to the serial hub and to the data acquisition computer.
Using defined IP addresses it is possible to(1) Connect directly to the Ethernet hub for testing.(2) Run the data acquisition software from a user computer for testing and software debug. or(3) Operate the Mini data collection software using either SSH or VNC connections.
Figure 6: PRP and its guest module. Figure 7: View of the module with open door. Across thetop shelf, left to right, are the 15 vdc power supply, theMac Mini and the Mini power supply.
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2 Installation and Startup
2.1 Packing List
The complete PRP system was delivered to ANL in two custom Storm shipping boxes. Theshipping list included ECCN numbers required by US customs.
BOX 1 -- RADIOMETERS
HEAD-MOTOR ASSEMBLY 6A002
RAD RADIOMETER PLATE 6A002
RAD BOX 4A101
GPS ZA005
IMPULSE CABLES
13.8 VDC POWER SUPPLY 3A226
BOX 2 -- ALL THE REST
CDU (FRSR-ETHERNET) BOX 4A101
MAC MINI COMPUTER 4A003
MINI POWER SUPPLY 4A003
NETGEAR ETHERNET SWITCH 4A003
UPS not incl
KEYBOARD AND MOUSE 4A003
NOTE: When unpacking be sure to save all the packing material.
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2.2 Unpacking
Refer to the hardware description below. The system can be unpacked and checked out in alaboratory environment before installation in the field environment.
Remove the FRSR head-motor assembly. Be careful of the MFR head. Be sure the pro-tective cap is covering the head diffuser. Check this assembly to be sure all screws are tight andthere is no damage in shipment.
Remove radiometers and plate. Carefully remove the radiometer plate. Be sure radiometer(PSP & PIR) domes are covered with soft cloth or optical wipe. Check all bolts and screws. Installthe shade plates and be sure the #2 screws are screwed in firmly.
Mind the head cable. The MFR head cable is the thick PVC cable with 18-pin Conexal plugsat each end. One end of this cable is marked with tape. This is the shield-connected end thatconnects to the CDU box. The MFR cable is delicate and should be treated with care. Do notflex or twist unnecessarily. Set the MFR cable aside and take care of it.
RAD Box. Remove the RAD box and set aside. Check that all screws and nuts are tight.
Remove the GPS. The GPS and its mounting pipe should be tight and in good condition.Remove and set aside.
Power supply The 15 vdc power supply possibly was shipped with the guest module (see de-scription). If you are going to run the system in the lab before taking it to the deployment siteyou will need (1) a 15 vdc, 2A power supply and 92) an ethernet switch as described below.
Remove the CDU box. As before check for damage and loose hardware.
Remove Mac Mini and Power Supply. If these were shipped with the guest module theywill need to be retrieved before performing a laboratory test.
Ethernet switch. The ethernet switch is used for laboratory testing. It is not needed fordeployment with the guest module as it has its own switch.
Check for all cables. The following cables should be in the shipment:10.3.1 – CDU to MFR head. This is described above. 10.3.2 –
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2.3 Selecting a deployment location
In general any deployment on land can be as shown in figure 6. Radiometers should be high andall at about the same level. A location in an open area with little or no shadows from nearby treesor structures is good. Especially, clear horizons in the direction of sunrise and sunset is important.
Shipboard Locations It is essential to choose the best, most exposed, location on a ship de-ployment.
Figure 8: Installing a combined FRSR-RAD PRP,Model 1, on the R/V Ron Brown.
Figure 9: With the new Model 2 PRP as designedfor AMF2, the RAD system can be deployed in-dependently from the FRSR, up to 200’ away. Inthis way the best possible unobstructed sky canbe obtained.
The following are considerations for deployment on a ship or other confined place::
• Exposed location. Minimal chance for shadows.
• Minimal RF interference and radar exposure.
• Accessable for occasional service such as dome cleaning.
• The RS232 serial connections to the sensor module should be less than 200’.
• Note that if the primary interest for the FRSR is measurements of AOD, τ , then it can belocated in a location where some solar shading might occur. However, the RAD radiometersshould be in the “best” exposed location.
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2.4 Install the hardware
Site RequirementsRAD mounting pole 1 1/2 in. (38 mm) Schedule 40 pipe. Mounted vertically in an
exposed location. A minimum of shading is critical.RSR mounting pole Same as above. Occasional shade is not as critical as for RAD since
the FRSR measures the direct solar beam.GPS mounting pole A 3/4 in. pipe with standard thread, mounted in an exposed loca-
tion.DAQ desk Desk space in an exposed location. The cable distance from FRSR
box to the switch should be 65 m (200 ft.) or less.Secure power A power supply capable of supplying 13.8 VDC at the FRSR box
(after line voltage drop). An uninterruptable supply is essential.
An installation checklist:
1. Align the FRSR plate so the north direction points to north. On a ship the plate shouldalign to the bow. Align to an accuracy of approximately ±5◦. A sketch of the RSR plateshowing the alignment can be found here.
2. RAD radiometers are at the same height as the head diffuser. As a rule any radiometershould not significantly shade the others down to the horizon.
3. GPS unit is exposed so it has good sky coverage (¿80%).
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2.5 Grounding
Proper grounding of the PRP is recommended and is essential in some applications. Ground lugsare provided and must be used.
Make all connections using a heavy gauge wire and then coat the ground lugs with waterproofcoating such as Scotchcoat or thick grease.
Check grounding continuity regularly with a good ohmmeter.
See Appendix G for details and different grounding schemes.
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2.6 Connections
Connect the modules together. All cables plug into the FRSR box. The connectors below showthe connectors and functions of the cables. Connector ‘8’ is the MFR cable on the left side of thebox. The WXT plug is used for the optional Vaisala WXT weather station. When there is nostation a dummy plug protects the connector.
PLUG 1 2 3 4 5 6 7 8DESC PWR ETH TCM MTR GPS RAD WXT MFR
2.6.1 The MFR head cable and Conxall connectors
As explained above the head cable construction is not particularly robust so great care should beexercised in handling it. The cheap Conxall connectors profess to be weather proof but they arenot up to the marine environment.
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PWR ETH TCM MTR GPS RAD WXT
FRSR BOX CONNECTORSFigure 10: Connectors on RSR box. Receptacle 8, for the MFR head is on the left side.
Figure 11: The Conxall connector at the CDU box. The head hasa matching connection. Note the sealing tape on the plug backshelland also the ground tape on the cable.
Figure 11 shows the head cable connected to the head. Several precautions should be observed:
1. Handle the cable carefully. Avoid twisting or bending the cable unnecessarily. Bend thecable in the same way it was bent in previous deployments.
2. The shield in the cable is connected to only one plug–to avoid ground loops–and the connectedend is marked by a wrap of electrical tape. This end of the cable goes to the CDU box.
3. Before deployment it is recommended that the plug backshell is properly sealed with self-sealing tape and a cover of Scotch 88 electrical tape. (The electrical tape protects the sealingtape from UV degradation.) This should be done on both ends.
4. Just before plugging in the cable for the last time before a deployment, rub just a dab ofsilicone grease into the receptacle female holes.
5. When plugging in the connector be sure the alignment key is correct, press the plug in slowly,and be sure the retaining ring snaps into place.
6. If you expect bad weather, as a precaution, wrap the connector at the box for a completeseal.
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2.6.2 Impulse underwater mateable connectors
The PRP uses the oceanographic grade, underwater mateable, connectors made by Impulse. TheImpulse connectors are the best choice for long-term use in the marine environment. Or any otherenvironment for that matter. Impulse connectors are immune to solar degradation and can beconnected either underwater or in rain.
Cold weather difficulty. The only drawback to Impulse connectors is that it is difficult to removethem in frozen conditions. When the temperature falls below 0◦C it is hard to make connectionsand very difficult to remove them. However, a hot air gun can warm up the connectors so theycan be removed.
2.7 Checking the PRP network
Device Dev IP Port DescriptionModule cooler 198.129.80.50 Control the internal hvac
Module UPS 198.129.80.49 Control AC power outlets in module.
PRP Hub 198.129.80.48 RS232 or RS485 to ethernet hub
TCM 198.129.80.48 10001 Tilt Compass Sensor
RAD 198.129.80.48 10003 RAD PRP & PIR Interfacel
RSR 198.129.80.48 10004 RSR circuit board
GPS 198.129.80.48 10005 External GPS
Mac Mini DAQ PC 198.129.80.47 DAQ computer, PRP data collection.
Module spare 198.129.80.46 Spare WiFi address.
Module spare 198.129.80.45 Spare WiFi address.
Module spare 198.129.80.44 Spare WiFi address.
Before checking the PRP, check the DAQ PC::
• The DAQ PC should be set up exactly as described in section 4.6.
• The PC ethernet port is set to manual IP with the address above. (198.129.80.47) or with thecorrect assignment defined for the installation.
• Network mask setting is set (per project IT instructions) to 198.129.80.0.
• Turn on the computer and open a terminal window (Unix or Linux). ‘cd’ to the prp2 softwarefolder. (Usually there is an alias set up for this step. Enter gtprp<enter> to see if the alias works.If not enter cd ~/prp2 and you should see the prompt ~/.../prp2/$ .
1. Check the setup file. The setup file is located at setup/anl_setup.txt. It is a text file thatholds all parameters used in all processing. To view the file only use the ‘less’ program:
$ less setup/anl_setup.txt
To edit the file you can used the ‘nano’ program:$ nano setup/anl_setup.txt
Be sure the IP addresses (For example SERIAL HUB URL: 198.129.80.46) and hub channeladdresses (For example RSR HUB COM NUMBER: 10004) agree with the above table or theassigned numbers for the installation.
2. Ping the hub If power is on and the ethernet connection to the PRP hub is active then a‘ping’ command should be successful. Enter the command
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ping 198.129.80.48
3. Check TCM connection. Enter “TCM<enter>” to connect to the TCM module.
These lines should come automatically once per second. The fields are compass, pitch, roll,and the X,Y,Z magnetic fields.
Break the TCM connection. Note: To break any Kermit connection enter “<control>\”followed by “q”. That is first hold down the control key and press ‘\’ then release and pressthe ‘q’ key.
4. Check RAD connection. Enter “RAD<enter>” to connect to the RAD module.
RAD Packet:$WIR07,10/03/06,21:02:00, 175, -253.4, 353.69, 19.20, 18.16, 262.54, 17.9, 11.9
These lines should come automatically every ten seconds. The fields are date, UTC, Nsam-ples, pir, LW, Tcase, Tdome, SW, Tcircuit, and Vbatt as described below. The LW and SWfields are the longwave and shortwave global downwelling irradiances in units of W m−2.
Disconnect as described above.
5. Check the GPS connection. Enter “GPS<enter>” to connect to the Garmin GPS.
These lines should come automatically every five seconds. The GPRMC fields are UTC time,status, latitude, N/S hemisphere, longitude, E/W hemisphere, speed over ground, course overground, magnetic variation, and date. The complete packet is described in section F.
Disconnect as described above.
6. Check RSR connection. Enter “RSR<enter>” to connect to the FRSR.
THE FRSR sends its data as Bin-Hex packets. The length of the packets depend on whetherthe FRSR is in a high or low operation mode.
These lines should come automatically every six seconds. The lines are decoded and printedby the data acquisition software.
Disconnect as described above.
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3 Operation
In this section we will present a step-by-step method to turn on the PRP, confirm operation of allcomponents, then how to begin data collection.
If the above connections are all successful then proceed to the remaining steps.
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3.1 Running the PRP data collection Program
Enter “PRP <enter>” to begin the data collection program.
3.2 Interpreting the PRP window
The PRP program accepts raw data strings from all the modules, sends them to the correctaveraging program then accepts the averaged data every two minutes.
Lines marked by “==> are raw data lines. Lines marked by *** are the outputs from the averagingprograms.
• TCMRW — The raw TCM data lines are collected by the data collection prograsm, G,written to the window and passed on to the TCM averaging program, avgtcm.pl. The rawline is
where the fields are yyyyMMdd, hhmmss, compass, pitch, roll, X magnetic field, Y field, Zfield, and on-board temperature. The TCM transmits a raw line each second.
• TCMAV — Each two minutes the program avgtcm.pl computes a set of statistics of thepast two minutes. The average line has a make up as below:
where the fields, separated by spaces, are year, month, day, hour, minute, second, mean pitch, stdev pitch, roll,stdev roll, compass, sigma compass, on-board temperature, X magnetic field, Y magnetic field, Z magneticfield. All angular quantities (pitch, roll, compass) are averaged as unit vectors.
• WIR09 — The NMEA-like output from the RAD occurs each 10-sec (default time) gives scalar averages ofthe RAD measurements:
where the comma delimited fields are the NMEA-style ID, date, time (from RAD real time clock), numberof samples averaged, mean PIR millivolts, computed longwave irradiance in W m−2, case temperature (◦C),dome temperature (◦C), shortwave irradiance, W m−2, on-board temperature (◦C), and input volts lessdiode drop.
• RADAV — The two-minute average from all raw records are returned as the space delimited averaged dataline.
where the fields are year, month, day, hour, minute, second (UTC time from data collection computer),shortwave irradiance ( W m−2), longwave irradiance ( W m−2), mean PIR millivolts, case temperature, dometemperature, on-board temperature, input voltage, and RSR control. The RSR control number can be -1,0, or 1. A value of -1 signals the PRP program to put the FRSR into low mode (park the shadowband). Avalue of 1 signals to put the FRSR into high mode. A value of 0 means do nothing.
• GPRMC — the standard NMEA GPS record provides all needed data for FRSR operation. The record isdescribed below.
1 UTC time of position fix, hhmmss format for GPS 17x HVS2 Status, A = Valid position, V = NAV receiver warning3 Latitude, ddmm.mmmm format4 Latitude hemisphere, N or S5 Longitude, dddmm.mmmm format6 Longitude hemisphere, E or W7 Speed over ground 000.0 to 999.9 knots (leading zeros will be transmitted)8 Course over ground, 000.0 to 359.9 degrees, true (leading zeros will be transmitted)9 UTC date of position fix, ddmmyy format10 Magnetic variation, 000.0 to 180.0 degrees (leading zeros will be transmitted)11 Magnetic variation direction, E or W (westerly variation adds to true course)Example: $GPRMC,000001,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3*66
• GPAV — is the output from the averaging program. Angular measurements, latitude, longitude, and course,are averaged as unit vectors.
There may be times, high winds, excess cold or icing, when the user would like to put the RSRinto a standby mode. During standby the shadowband is parked in its nadir position.
From the keyboard enter “H <enter>”. The FRSR will go to high mode operation and the shad-owband will begin to function.
Enter “L <enter>” to put the FRSR into low mode. The shadowband will stop rotating.
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3.4 Operation Checklist
This section provides a list of items to routinely check during a PRP operational period.
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4 Hardware Overview
Figure 12: System block diagram.
4.1 The Control Data Unit
4.1.1 Ethernet-Serial Hub
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Figure 13: The ICP-DAS Five-port ethernet hub
4.2 The Rotating Shadowband Radiometer
4.2.1 RSR Tattletale Program, FRSR.c
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4.3 The Tilt-Compass module (TCM)
4.4 The GPS
GPS17X
NMEA string GPRCM set for every 10 seconds.
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Figure 14: RSR plate assembly.
Figure 15: Definitions of pitch and roll.
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4.5 The RAD Unit
Figure 16: RAD assembly.
4.5.1 RAD Software
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4.6 The Data Acquisition Unit
PC running Linux (Umbuntu) orMac OS X 10.6.2 for development.
4.6.1 Required Software
KERMIT A powerful serial interface program available from Columbia University. Books onC-Kermit, the latest software, are available and very useful.
PERL Standard PERL software that is available in most Unix/Linux installations.
PERL, Math-MatrixReal-2.0 A special package for matrix manipulations. It is available from CPAN.
EXPECT (TCL) Expect is a Unix automation and testing tool, written by Don Libes as an ex-tension to the Tcl scripting language, for interactive applications such as telnet,ftp, passwd, fsck, rlogin, tip, ssh, and others. It uses Unix pseudo terminals towrap up subprocesses transparently, allowing the automation of arbitrary applica-tions that are accessed over a terminal. Expect and TCL are available in manyUnix/Linux installations. In a terminal window enter expect -v and the reply willbe expect version 5.44.1.11. Version 5 or greater is recommended.
R R is a free software environment for statistical computing and graphics. It compilesand runs on a wide variety of UNIX platforms, Windows and MacOS.
4.6.2 Directory Tree
/home
/prp2
/data
(all data files are located here)
/setup
(the setup file with all operational paremeters are in this directory)
setupfile.txt -- example setup file name
4.6.3 Settings in ‘bashrc’
# WINDOW FORMAT
set prompt = ’%c1>> ’
alias myalias "less ~/.tcshrc"
## PRP2
set mypath = "/Users/rmr/swmain/apps/prp2"
alias gtprp2 "cd $mypath"
alias RAD "cd $mypath; ./term_to_rad.ex"
alias TCM "cd $mypath; ./term_to_tcm.ex"
alias GPS "cd $mypath; ./term_to_gps.ex"
alias RSR "cd $mypath; ./term_to_rsr.ex"
alias PRP "cd $mypath; ./G ’setup/test_setup.txt’"
alias AOD "cd $mypath; ./AOD.pl setup/test_setup.txt"
A sun photometer measures the directional solar irradiance in discrete wavelength channels alonga vector from the instrument detector to the solar disk. The atmosphere both absorbs and scatterslight along this vector, and these effects are treated together through the mass extinction crosssection, kλ (Liou 1980). Because the different scattering and absorbing processes may be assumedto be independent of each other, the total extinction coefficient is a simple sum from all thecontributors:
kλ = kA + kR + kO + kN , (1)
where the terms on the right represent the mass extinction cross sections for aerosol scattering,Rayleigh scattering, ozone ( O3) absorption, and nitrogen dioxide (NO2) absorption.
A parallel beam of radiation, denoted by its irradiance, Iλ, will be reduced in the direction of itspropagation by an amount given by
dIλ = −kλ ρ Iλ ds, (2)
where kλ is defined by (1), ρ is the air density, and ds is the differential path length. If kλ isconstant, the classical Beer-Bouguer-Lambert law results:
Iλ(s2) = Iλ(s1)e−kλu, (3)
where u =∫ρ ds is called the optical thickness or optical path and integration proceeds along the
path the ray takes from s1 to s2.
In the atmosphere kλ and ρ are not homogeneous and so the full integration of (2) is required.A reasonable approximation is that the atmosphere is horizontally stratified, and this allows in-tegration of (2) along the vertical axis, z, in a coordinate system on the Earth’s surface. Thends = sec θ dz, and
Iλ(h) = IλT exp
(−∫ ∞h
kλ ρ sec θ dz
), (4)
where Iλ(h) is the irradiance at the observer at height h above sea level, and IλT is the irradiance atthe top of the atmosphere. Integration follows the ray in its refracted path through the atmosphereand, for completeness, must include the curvature of the Earth.
In the case that kλ is constant through the air column, as in Rayleigh scattering, it can be movedoutside the integral. In the cases when it is non-uniform in the column, as for aerosol, O3, andNO2, an effective extinction coefficient can be defined. The resulting effective total extinctioncoefficient is given by k̃λ = k̃A + kR + k̃O + k̃N and is defined by∫ ∞
h
kλ ρ sec θ dz = k̃λ
∫ ∞h
ρ sec θ dz = τλ
[∫ρ sec θ dz∫ρ dz
]. (5)
The terms with tildes are effective mean values that produce the same extinction if uniformlydistributed through the atmosphere. The bracketed fraction is defined as the air mass, m(θ) and isa function of the zenith angle, θ. When the solar beam is normal to the geoid, m = 1, the normalatmospheric optical thickness (AOT) is defined as
τλ =
∫ ∞h
kλ ρ dz = k̃λ
∫ ∞h
ρ dz . (6)
The resulting formulation for the irradiance becomes
Iλ(h) = IλT e−(τA+τR+τO+τN )m(θ) , (7)
which is a working analog to the classical Beer-Bouguer-Lambert equation, (3). Without knowingthe vertical and horizontal distribution of the different contributing attenuators, (7) serves as
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definition of the optical thicknesses which must be derived by observation of the extinction of thesolar beam through the atmosphere.
The instantaneous solar irradiance at the top of the atmosphere, IT , is the solar constant modulatedby the Earth-Sun distance, IλT = Iλ0/r
2, where Iλ0 is the mean solar irradiance at the top of theatmosphere and r is the ratio of the Earth-sun distance to its mean value (Paltridge and Platt 1977):
r = 1 − ε cos (a [J − 4]) , (8)
where ε = 0.01673 is the eccentricity of orbit, and J is the day of the year (sometimes referred toas the Julian day). The r2 correction results in an annual modulation of Iλ0 of approximately 6%.This is comparable to an uncertainty of about 5% in the measured solar spectrum (see Colina etal. 1996) (Fig. ??).
The air mass, m(θ), is a function of the path of the ray through the atmosphere. When refractionand the Earth curvature are ignored, the simple equation m = sec θT , where θT is the solar zenithangle at the top of the atmosphere, can be used. This approximation is accurate to within 1%when θT ≤ 70◦. Kasten and Young (1989) include both curvature and refraction into a formulationof air mass and use the ISO standard atmosphere for density and index of refraction. They usean index of refraction profile at 700 nm for all wavelengths and then fit the computations to anempirical curve,
m(θr) ≈1
cos θr + a (b− θr)−c , (9)
where θr is the solar zenith angle at the observer, in radians, a = 0.50572, b = 96.07995, andc = 1.364. A pointing sun photometer locates the solar beam and thus automatically measuresθr but a shadowband instrument must compute it. The ephemeris algorithm by Michalsky (1988;Spencer 1989) is used to determine θr and θT given the time and geographic position of the observer,and including refraction and curvature.
In (7), the last three normal optical thickness terms can be determined by a combination ofmeasurements and theory. Raleigh scattering is well understood and τR can be computed bytheoretical formulation. Tables of Rayleigh scattering coefficient, using the relationships fromPenndorf (1957), were computed for each channel wavelength and for the atmospheric pressure atthe time of the measurement with an empirical equation:
τR =
(p
p0
) [a1λ
4 + a2λ2 + a3 + a4λ
−2]−1 (10)
where (a1, a2, a3, a4) = (117.2594, −1.3215, 0.00032073, −0.000076842), p is the atmospheric pres-sure in hPa at the time of the measurement, p0 = 1013.25 hPa, and λ is the wavelength in µm.
The ozone optical thickness can be computed from measurements of the ozone distribution orinferred from known ozone climatology. The ozone corrections used in this paper are quite smalland were provided by the NASA (Menghua Wang 1999, personal communication)
A.1 Calibration considerations
Photometric instruments measure light through a bandpass filter and so all wavelength dependencymust be integrated over the filter bandpass. Each detector has a different response function, wi(λ),where i is the detector (channel) number. Each detector-filter response is calibrated relative toits maximum value at its center wavelength, λi, and wi(λi) ≡ 1. Its values at other wavelengthsare referenced to its response at λi. The measured irradiance is related to the actual incidentirradiance by the integral
Ii =
∫∞0wi(λ) Iλ dλ∫∞
0wi(λ) dλ
, (11)
26
and all references to irradiance as measured by an instrument imply the above weighted meanbased on a known bandpass filter response. The bandwidth of the filter is defined as the width ofa top hat unity-response function with the same area as the actual response
∆λi =
∫ ∞0
wi(λ) dλ . (12)
In all discussions after this point, the λ-subscript will be dropped unless it is necessary for clar-ity. All development refers to monochromatic light and wavelength dependency is implicit. Theinstrument bandpass and its effect on a spectrum of light is also hereafter implied. The discussionbelow is applied to all channels in the same fashion, and so unless it is necessary for clarity, the isubscript will be omitted.
Taking the natural log of both sides of (7) results in the classic Langley relationship:
ln(IN ) = −τ m+ ln(IT ) , (13)
where τ = (τA + τR + τO), and IN is the measured irradiance of the solar beam referenced to aplane that is normal to the solar beam and excluding all scattered diffuse light. In the Langleymethod (Shaw 1983; Harrison and Michalsky 1994a) a plot of m versus ln(IN ) can be extrapolatedto m = 0 to derive ln(IT ). The negative of the slope of the line is τ . The Langley method workswhenever the skies are perfectly clear, no cirrus or other layers are present, and if τ is constant overthe time duration of the observations. In practice, a Langley plot can be produced from aboutone hour of clear sky in the early morning just after sunrise or late evening just before sunsetwhen 2 < m < 6 (60 < θr < 80◦). All measurements of IN are plotted on a log-linear plot anda best estimate straight line is fitted to the data. For sites other than ideal calibration locations,such as the Mauna Loa Observatory described below, a median-fitting algorithm provides the bestobjective fit to the data. Over the ocean, there are almost always clouds on the horizon. In thetropics these are usually high cumulus clouds or cirrus. As a result, Langley plots from ships arerare gems that must be collected whenever they occur.
Langley plots are constructed as often as possible as a quality assurance tool because they providean excellent means of detecting calibration changes. The top-of-the-atmosphere irradiance, IT , de-pends on the Sun-Earth separation, but its mean value, I0 = IT r
2, should not change significantlyover time. The absolute calibration of the instrument can be compared to the mean reference solarirradiance at the top of the atmosphere, Ii REF , (Colina et al.1996) by integrating the referencesolar spectrum over the bandpass of the sensor (see Eq. 11) to obtain
I0REF =
∫∞0w (λ) IREF (λ) dλ∫∞
0w (λ) dλ
. (14)
In a well-calibrated absolute instrument, I0 ≈ I0REF . However, as long as the calibration con-stant, I0, is constant, as determined from multiple Langley plots, accurate AOT estimates arepossible. While many investigators use raw voltages to calibrate their instruments, the extra stepof computing I0 is important since it defines the radiative impact of the aerosol at the surface.
Once I0 is established for an instrument, (13) is used to estimate aerosol optical thickness for eachinstantaneous measurement of IN . From the time and geographic location of the measurement, ITcan be computed from the calibration constant, IT = I0/r
2 and m can be computed accurately from(9) or estimated by sec θT . After the contributions by Rayleigh scattering and ozone absorptionare accounted for, τA remains.
A.2 Theory of Shadowband Radiometers
An estimate of τ can be made for every measurement of the solar beam irradiance, IN , whenthere are no clouds in front of the solar disk. Two sun photometer designs are commonly used:
27
a narrow-beam detector mechanically pointed in the direction of the sun or a wide-field-of-viewradiometer with a solar occulting apparatus. The first type of sun photometer (see Holben etal. 1998) requires careful angular positioning but can provide additional information on forwardscattering phase functions and thus help characterize the aerosol constituents. The latter typeof radiometer, a shadowband radiometer, measures the diffuse and global (upper hemispheric)irradiance and computes IN as the difference between the two. The device gets its name from thehemispherical metal strip that rotates around the detector and blocks the direct solar beam toyield a signal that is from the sky only (after the effect of the arm is included).
One of the first rotating shadowband devices was a broadband device introduced by Wesely (1982).A more advanced broadband instrument using a thermopile-type broadband pyranometer has beendeveloped by Long (1996a). The Multi-Frequency Rotating Shadowband Radiometer (MFRSR),developed by Harrison et al. (1994) uses independent interference-filter-photodiode detectors andan automated rotating shadowband technique to make spatially resolved measurements at sevenwavelength passbands. The MFRSR achieves an accuracy in direct-normal spectral irradiancecomparable with that of narrow-beam tracking devices. A significant advantage of the shadowbandtechnique is that the global and diffuse irradiance measurements can be used to study overallradiative budgets (Long 1996). Our FRSR makes use of the MFRSR detector head.
The shadowband radiometer must properly measure the global and diffuse irradiances from whichthe direct-beam irradiance is derived by the subtraction
IH = IG − ID , (15)
where IH is the direct-beam irradiance projected onto a horizontal plane, IG is the global irradianceon the horizontal plane, and ID is the diffuse irradiance from non-forward scattering. The globalirradiance, IG, is measured when the band is out of the field of view and the sensor is exposed tofull sunlight. The irradiance normal to the incident beam is computed by
IN = IH sec θr . (16)
A correction for the amount of sky that is blocked by the occulting band is essential for an accuratemeasurement. An automatic correction for the shadowband is possible through measurement of“edge” irradiance as is done with the land-based MFRSR. The shadow irradiance, IS , occurs whenthe sun is completely covered by the shadowband, but a portion of the diffuse irradiance is alsoblocked. The edge irradiance, IE , is measured when the band is just to one side of the solar disk andprovides a good estimate of the global irradiance minus the portion of sky that is blocked by theshadowband at the time it blocks the solar disk. In practice, IE is selected from two measurementstaken when the shadow is on one side or the other of the diffuser. Generally an average is taken,but in some cases in the early morning or late evening only one of the edges is acceptable. It iseasy to show that the fully-corrected horizontal beam irradiance is
IH = IE − IS . (17)
An advantage of using (17) is that with the fast-rotating technique the edge and shadow measure-ments are made in a very short time which reduces noise significantly, especially on partly cloudydays. Also, if the electronics have a constant bias, the bias is removed by the subtraction.
28
Figure 17: Shortwave spectrum
29
B Indented Part List
The partlist here will define every part in the PRP2. To refer and find informationon any part, and this includes manuals, calibrations, and any pertinent information,one can find the part number from this list then go to the parts documentationonline.
PRP2 INDENTED PART LISTPRP2 INDENTED PART LISTPRP2 INDENTED PART LISTPRP2 INDENTED PART LIST Edit: 4/29 2011pn ECCN 1 2 3 4 5 6 7 DESCRIPTION1 PRP2 MECHANICAL ASSEMBLYPRP2 MECHANICAL ASSEMBLYPRP2 MECHANICAL ASSEMBLYPRP2 MECHANICAL ASSEMBLYPRP2 MECHANICAL ASSEMBLYPRP2 MECHANICAL ASSEMBLYPRP2 MECHANICAL ASSEMBLY The complete prp2 assembly delivered to Argonne10 6A992 FRSR ASSEMBLYFRSR ASSEMBLYFRSR ASSEMBLYFRSR ASSEMBLY COMPLETE FRSR ASSEMBLY AND CABLE TO DAQ10.1 PLATE, FRSRPLATE, FRSRPLATE, FRSR Plate complerte assembly with motor, shadowband and tilt sensor.10.1.1 PLATEPLATE The FRSR plate with all mounting hardware.10.1.1.1 PLATE BLANKPLATE BLANKPLATE BLANK Blank plate with holes.10.1.1.2 BRACE, MFR BRACKET, TOPBRACE, MFR BRACKET, TOPBRACE, MFR BRACKET, TOP SS triangular brace that holds the MFR head.10.1.1.3 BRACE, MRF BRACKET, BOTTOMBRACE, MRF BRACKET, BOTTOMBRACE, MRF BRACKET, BOTTOM SS triangular brace that holds the MFR bracket at the plate.10.1.1.4 BRACKET, MFR HEADBRACKET, MFR HEADBRACKET, MFR HEAD SS bracket that supports the MFR head.`10.1.1.5 SUPPORT FOR MOTOR HOUSINGSUPPORT FOR MOTOR HOUSINGSUPPORT FOR MOTOR HOUSING Support for the motor housing10.1.1.6 MOTOR BRACKETMOTOR BRACKETMOTOR BRACKET Bracket that holds the motor housing10.1.1.7 PIPE MOUNT ASSEMBLYPIPE MOUNT ASSEMBLYPIPE MOUNT ASSEMBLY Pipe mount, same as RAD10.1.1.7.1 PIPE MOUNT PLASTIC PIECEPIPE MOUNT PLASTIC PIECE Pipe mount 10.1.1.7.2 SCREW, TIGHTENINGSCREW, TIGHTENING Tightening screw, pipe mount, 1/4-20 x 1" overall length, 316SS10.1.1.7.3 SCREW, PINSCREW, PIN Screw that tightenens the fitting, 1/4-20 x 1/2" overall length, 316SS10.1.1.7.4 BOLTS, MOUNTBOLTS, MOUNT Bolts (4) 1/4-20 x 3/4" hex cap screws, 316SS10.1.1.7.5 WASHER, FLAT, PIPE MOUNTWASHER, FLAT, PIPE MOUNT Washer, flat, 1/4 316SS (4)10.1.1.7.6 WASHER, LOCK, PIPE MOUNTWASHER, LOCK, PIPE MOUNT Washer, split lock, 1/4 316SS (4)10.1.1.8 BOLTS, MOTOR SUPORTBOLTS, MOTOR SUPORTBOLTS, MOTOR SUPORT Cap screws (4), 10-32 x 3/4" long, 316SS, 10.1.1.9 WASHERS, MOTOR BRACKETWASHERS, MOTOR BRACKETWASHERS, MOTOR BRACKET Flat washers for motor support and bracket. (4) #10, 316SS, 10.1.1.10 WASHERS, LOCK, MOTOR BRACKETSWASHERS, LOCK, MOTOR BRACKETSWASHERS, LOCK, MOTOR BRACKETS Lock washers for motor support brackets, (4) #10, 316SS10.1.1.11 SCREWS FOR MOTOR BRACKETSCREWS FOR MOTOR BRACKETSCREWS FOR MOTOR BRACKET Screws for motor housing to bracket (2), FH #10-32 x 1/2", 316SS10.1.1.12 BOLTS FOR HEAD BRACKETBOLTS FOR HEAD BRACKETBOLTS FOR HEAD BRACKET Cap screws for head bracket to plate. (3) 6-32 x 5/8", 316SS10.1.1.13 BOLTS FOR BRACKET SUPPORTSBOLTS FOR BRACKET SUPPORTSBOLTS FOR BRACKET SUPPORTS Pan head, Phillips (2) 6-32 x 1/2", 316SS10.1.1.14 WASHERS FOR BRACKETWASHERS FOR BRACKETWASHERS FOR BRACKET Washer, flat, (3) #6, 316ss10.1.1.15 LOCK WASHERS FOR BRACKETLOCK WASHERS FOR BRACKETLOCK WASHERS FOR BRACKET Washers, lock (3) #6, 316ss10.1.1.16 SCREWS FOR MFR HEADSCREWS FOR MFR HEADSCREWS FOR MFR HEAD Bolt head to bracket. FH, Philips, 6-32 x 0.7"long, 316SS
10.1.2 MOTOR ASSYMOTOR ASSYMOTOR ASSYMOTOR ASSY Motor housing, nadir switch, shadowband.
10.1.2.1 HOUSING, MOTORHOUSING, MOTORHOUSING, MOTORCylinder and end cap. Aluminum. Powdercoat thermoplastic, white. (Mask holes for connector and shaft.) Observe o-ring surfaces.
10.1.2.1.1 CYLINDERCYLINDER Aluminum cylinder with holes for hardware.10.1.2.1.2 END CAPEND CAP Aluminum with o-ring groves and threaded hole for Impulse recep.10.1.2.1.3 SCREWS, END CAPSCREWS, END CAP Cap screws, 4-40, 3/8" for end cap. (4 req)10.1.2.1.4 O-RINGS, END CAPO-RINGS, END CAP O-rings for the end cap (2 req)
10.1.2.2 BRACKET ASSY, NADIR SWITCHBRACKET ASSY, NADIR SWITCHBRACKET ASSY, NADIR SWITCHThe nadir switch bracket assembly screws into the back of the motor housing and hold the motor/gear and the nadir switch circuit board.
10.1.2.2.1 BRACKETBRACKET This is the bare bracket, aluminum.10.1.2.2.2 SCREWS, BRACKET MOUNTSCREWS, BRACKET MOUNT Bolt, washer, & lock washer for bracket to housing fasten.10.1.2.2.3 SCREWS, PCB MOUNTSCREWS, PCB MOUNT Bolt & washer for PCB mount to the bracket.10.1.2.2.4 SCREWS, MOTOR TO BRACKETSCREWS, MOTOR TO BRACKET Metric screws to bolt the motor-gear to the bracket.10.1.2.2.5 WASHERS, NYLON, PCB_TO_BRWASHERS, NYLON, PCB_TO_BR Nylon insulating washers to preven shorting.
10.1.2.3 SHAFT, SHADOWBANDSHAFT, SHADOWBANDSHAFT, SHADOWBAND Connects to the gear shaft and pokes through the motor housing.
10.1.2.3.1 SHAFT, MACHINED PIECESHAFT, MACHINED PIECE10.1.2.3.2 O-RING (2) O-RING (2) O-rings seal the shaft through the housing wall.10.1.2.3.3 SETSCREWSETSCREW Holds the shaft onto the gear shaft.10.1.2.3.4 MAGNET, NADIRMAGNET, NADIR10.1.2.4 CIRCUIT BOARD, NADIR SWITCHCIRCUIT BOARD, NADIR SWITCHCIRCUIT BOARD, NADIR SWITCH Electronic circuit with Hall effect switch and driver circuitry.10.1.2.4.1 BLANK, PCB, NADIR SWBLANK, PCB, NADIR SW Blank circuit board.10.1.2.4.2 SWITCH, HALL EFECTSWITCH, HALL EFECT Semiconductor (allegro 1361ELT or equivalent)10.1.2.4.3 TRANSISTOR, PNP,TRANSISTOR, PNP, Driver for switch. Open collector.10.1.2.4.4 COMPONENTS, ELEC, PCBCOMPONENTS, ELEC, PCB Diode, resistor, etc.10.1.2.4.5 CONNECTOR, INTERNAL, CONNECTOR, INTERNAL, Header 2x3 Ampmodu, Digikey A26708, To decouple the end cap from the
motor & nadir switch. Mates with Plug#101271 (A25830-ND)
10.1.2.6 √ SHADOWBANDSHADOWBANDSHADOWBAND shadowband as developed for the BNL PRP.
10.1.2.6.1 SHADOWBANDSHADOWBAND Shadowband per BNL.10.1.2.6.2 SET SCREWSET SCREW Set screw for the motor shaft.10.1.2.6.3 COLLAR, SHAFTCOLLAR, SHAFT Connects to the shadowband and mates to the motor shaft.10.1.2.6.4 SCREWS, COLLAR (2)SCREWS, COLLAR (2) Flat head screws that fasten the shadowband to the collar.10.1.2.7 √ RECEP, MOTOR, ASSYRECEP, MOTOR, ASSYRECEP, MOTOR, ASSY Impluse 4-pin, assembly with internal wiring and connector.10.1.2.7.1 RECEPTACLE, IMPULSE BHRRECEPTACLE, IMPULSE BHR Impulse receptacle, BHR10.1.2.7.2 CONNECTOR, IN LINE INTERNALCONNECTOR, IN LINE INTERNAL Mates with #101245, Ampmodu 2x3 male, Digikey A2583010.1.2.8 MOTOR/GEAR ASSEMBLYMOTOR/GEAR ASSEMBLYMOTOR/GEAR ASSEMBLY Maxon motor-gear combination.10.1.3 TILT ASSYTILT ASSYTILT ASSY Small Rose box with PNI tilt sensor mounts of the FRSR plate.10.1.3.1 BOX, TILTBOX, TILTBOX, TILT Rose-Bopla box with machined holes for receptacles.10.1.3.1.1 BOX, TILT, BLANKBOX, TILT, BLANK Rose-Bopla box off the shelf.10.1.3.1.2 PLATE, PCB, INTERIORPLATE, PCB, INTERIOR Plate to holt the tilt sensor in the Rose box.10.1.3.1.3 SCREWS, FASTEN PLATE IN BOXSCREWS, FASTEN PLATE IN BOX10.1.3.1.4 STANDOFF, TCM BOARD (4)STANDOFF, TCM BOARD (4)10.1.3.1.5 SCREWS FOR ABOVE (4)SCREWS FOR ABOVE (4)10.1.3.1.6 WASHERS FOR ABOVE (4)WASHERS FOR ABOVE (4)10.1.3.1.7 NUTS FOR ABOVE (4)NUTS FOR ABOVE (4)10.1.3.2 TCM2.5 TILT SENSORTCM2.5 TILT SENSORTCM2.5 TILT SENSOR PNI tilt sensor, damped fluid.10.1.3.3 RECEP, TILT, ASSYRECEP, TILT, ASSYRECEP, TILT, ASSY Impulse BHR10.1.3.3.1 BH RECEPTICLE, IMPULSEBH RECEPTICLE, IMPULSE10.1.3.3.2 CONNECTOR, TCMCONNECTOR, TCM Connector, Molex Series KK, Connector Housing
10.1.3.4 BOLTS, BOX TO PLATE (2)BOLTS, BOX TO PLATE (2)BOLTS, BOX TO PLATE (2)10.1.3.5 WASHERS, FOR ABOVE (4)WASHERS, FOR ABOVE (4)WASHERS, FOR ABOVE (4)10.1.3.6 WASHERS, LOCK, FOR ABOVE (2)WASHERS, LOCK, FOR ABOVE (2)WASHERS, LOCK, FOR ABOVE (2)10.1.3.7 NUTS, FOR ABOVENUTS, FOR ABOVENUTS, FOR ABOVE10.1.4 MOTOR BRACKETMOTOR BRACKETMOTOR BRACKETMOTOR BRACKET The mounting pieces to mount the motor housing to the FRSR plate.10.1.4.1 BRACKETBRACKETBRACKET Bracket blank, aluminum.10.1.4.2 BOLT SET, PLATE (2)BOLT SET, PLATE (2)BOLT SET, PLATE (2) Bolts to fasten the bracket to the FRSR plate.10.1.4.3 BOLT SET, HOUSING (2)BOLT SET, HOUSING (2)BOLT SET, HOUSING (2) Bolts to fasten the housing to the bracket. (10-32)10.1.5 PIPE MOUNTPIPE MOUNTPIPE MOUNT Full pipe mount assembly with hardware.10.1.5.1 MOUNT, BLANKMOUNT, BLANKMOUNT, BLANK Blank mount, with helicoils.10.1.5.2 BOLT SET, TIGHTENINGBOLT SET, TIGHTENINGBOLT SET, TIGHTENING Bolt to clamp the fitting to a pipe.10.1.5.3 BOLT, SET BOLT, SET BOLT, SET Set screw bolt.10.1.5.4 BOLT SETS (4) PLATEBOLT SETS (4) PLATEBOLT SETS (4) PLATE Bolt sets for fastening the plate to the pipe mount.10.1.6 MFR HEAD ASSYMFR HEAD ASSYMFR HEAD ASSYMFR HEAD ASSY Multifrequency head and mounting hardware.10.1.6.1 6A992 MFR HEADMFR HEADMFR HEAD Complete head assembly. Provided from ARM/ACRF SGP10.1.6.2 BRACKET, MFR HEADBRACKET, MFR HEADBRACKET, MFR HEAD Bracket piece to mount head to the plate.10.1.6.2.1 BRACKET VERTICAL PLATEBRACKET VERTICAL PLATE10.1.6.2.2 BOTTOM GUSSETBOTTOM GUSSET10.1.6.2.3 TOP GUSSETTOP GUSSET10.1.6.2.4 SCREWS (2), B. GUS'T TO PLATESCREWS (2), B. GUS'T TO PLATE10.1.6.2.5 SCREWS (2), B.GUS'T TO BRAC.SCREWS (2), B.GUS'T TO BRAC.10.1.6.2.6 SCREWS (2), T. GUS'T TO BRAC.SCREWS (2), T. GUS'T TO BRAC.10.1.6.3 SCREWS (2) , MFR HD TO BRACKETSCREWS (2) , MFR HD TO BRACKETSCREWS (2) , MFR HD TO BRACKET FH screws to fasten the MFR head to the bracket.10.1.6.4 SCREWS (2), MFR BRACKET TO PLATE.SCREWS (2), MFR BRACKET TO PLATE.SCREWS (2), MFR BRACKET TO PLATE.Screws/bolts, washers, nuts to fasten the MFR bracket to the plate.10.1.6.5 WASHERS (2), FLAT FOR ABOVEWASHERS (2), FLAT FOR ABOVEWASHERS (2), FLAT FOR ABOVE10.1.6.6 WASHERS (2), LOCK FOR ABOVEWASHERS (2), LOCK FOR ABOVEWASHERS (2), LOCK FOR ABOVE10.2 4A101 CDU/IFCDU/IF CONTROL DATA UNIT AND MULTIPORT INTERFACE, COMPLETE1021 PCB CDUPCB CDU Complete electronic circuit board.10211 TT8 microcomputerTT8 microcomputerTT8 microcomputer Microcomputer for control and data unit.10212 Electronic partsElectronic partsElectronic parts Misc electronic parts for the CDU board.10213 PCB blankPCB blankPCB blank Blank circuit card.10.2.2 MULTIPORTMULTIPORTMULTIPORT ICP PDS-752 multiport10.2.3 CDU BOXCDU BOX Complete box assembly10.2.3.1 BOX, CDUBOX, CDUBOX, CDU Rose-Bopla box with holes for eight (8) connectors.10.2.3.2 BOX HDWR, PLATE, GROUND SCREWSBOX HDWR, PLATE, GROUND SCREWSBOX HDWR, PLATE, GROUND SCREWSInternal mounting plate for CDU board and multiport.10.2.3.3 RECEP, MFRRECEP, MFRRECEP, MFR Conxall, 18p10.2.3.4 RECEP, RADRECEP, RADRECEP, RAD Impulse BHR, 6S, mates 10.3.210.2.3.5 RECEP, TILTRECEP, TILTRECEP, TILT Impulse BHR, 6S, mates 10.3.310.2.3.6 RECEP, SHADOWBAND MOTORRECEP, SHADOWBAND MOTORRECEP, SHADOWBAND MOTOR Impulse BHR, 4S, mates 10.3.410.2.3.7 RECEP, GPSRECEP, GPSRECEP, GPS Impulse BHR, 6S, mates 10.3.610.2.3.8 RECEP, POWERRECEP, POWERRECEP, POWER Impulse BHR, 3S, mates 10.3.710.2.3.9 RECEP, ETHERNETRECEP, ETHERNETRECEP, ETHERNET Ethernet connector, sealed RJ45, ENSP1F510.2.3.10 RECEP, WXTRECEP, WXTRECEP, WXT Impulse BHR, 8S, mates 10.3.510.2.3.11 FILTER BOARD FOR MFR PLUGFILTER BOARD FOR MFR PLUGFILTER BOARD FOR MFR PLUG Filter board that goes onto the coxall (10.2.3.3)10.2.4 MOUNT PLATEMOUNT PLATEMOUNT PLATEMOUNT PLATE Plate for mounting the CDU box to a pipe.10.3 CABLE SET, CDUCABLE SET, CDUCABLE SET, CDUCABLE SET, CDU10.3.1 CABLE, CDU TO MFR HEADCABLE, CDU TO MFR HEADCABLE, CDU TO MFR HEADCABLE, CDU TO MFR HEAD Conxall cable from MFR head to CDU box.10.3.2 CABLE, CDU TO RADCABLE, CDU TO RADCABLE, CDU TO RADCABLE, CDU TO RAD Impulse cable, RAD to CDU10.3.3 CABLE, CDU TO TILTCABLE, CDU TO TILTCABLE, CDU TO TILTCABLE, CDU TO TILT Impulse cable, Tilt to CDU10.3.4 CABLE, CDU TO SHADOWBAND MOTORCABLE, CDU TO SHADOWBAND MOTORCABLE, CDU TO SHADOWBAND MOTORCABLE, CDU TO SHADOWBAND MOTOR Impulse cable, Motor to CDU10.3.5 CABLE, CDU TO WXTCABLE, CDU TO WXTCABLE, CDU TO WXTCABLE, CDU TO WXT Impulse cable, WXT to CDU10.3.6 CABLE, CDU TO GPSCABLE, CDU TO GPSCABLE, CDU TO GPSCABLE, CDU TO GPS Impulse cable, GPS to CDU10.3.7 CABLE, CDU POWERCABLE, CDU POWERCABLE, CDU POWERCABLE, CDU POWER Impulse cable, CDU to DAQ power supply10.3.8 CABLE, CDU ETHERNETCABLE, CDU ETHERNETCABLE, CDU ETHERNETCABLE, CDU ETHERNET Impulse cable, CDU to DAQ computer20 4A101 RADRAD RADIOMETER ANALOG-DIGITAL INTERFACE20.1 RAD INSTRUMENT PLATERAD INSTRUMENT PLATERAD INSTRUMENT PLATERAD INSTRUMENT PLATERAD INSTRUMENT PLATERAD INSTRUMENT PLATE Plate with PSP & PIR radiometers.20.1.1 RAD PLATERAD PLATERAD PLATE Blank plate. From machine shop.20.1.2 BOLT SET, PSP/PIR, (6 SETS)BOLT SET, PSP/PIR, (6 SETS)BOLT SET, PSP/PIR, (6 SETS)BOLT SET, PSP/PIR, (6 SETS)BOLT SET, PSP/PIR, (6 SETS) Bolts, washers, nuts for radiometers. 6 bolts, 6 nuts, 12 flats, 6 locks20.2 PIPE MOUNTPIPE MOUNTPIPE MOUNT Full pipe mount assembly with hardware.20.2.1 MOUNT, BLANKMOUNT, BLANKMOUNT, BLANKMOUNT, BLANK Blank mount, with helicoils. From the machinist.20.2.2 BOLT, CLAMP, TIGHTENINGBOLT, CLAMP, TIGHTENINGBOLT, CLAMP, TIGHTENINGBOLT, CLAMP, TIGHTENINGBOLT, CLAMP, TIGHTENING Bolt to clamp the fitting to a pipe.20.2.3 BOLT, SET SCREWBOLT, SET SCREWBOLT, SET SCREWBOLT, SET SCREWBOLT, SET SCREW Set screw bolt. firms up the clamp onto a pipe.20.2.4 BOLT SETS (4) PLATEBOLT SETS (4) PLATEBOLT SETS (4) PLATEBOLT SETS (4) PLATEBOLT SETS (4) PLATE Bolt sets for fastening the plate to the pipe mount. (bolt-washers-nuts)20.3 PSPPSP Eppley Labs, PSP. Standard model assembly with shade plates.20.3.1 PSP SENSORPSP SENSORPSP SENSOR Basic PSP sensor. Standard brass housing.20.3.2 SHADE PLATESHADE PLATESHADE PLATE Shade plate from Eppley.20.3.3 SCREWS, SHADE PLATE (3 RQD)SCREWS, SHADE PLATE (3 RQD)SCREWS, SHADE PLATE (3 RQD)SCREWS, SHADE PLATE (3 RQD)SCREWS, SHADE PLATE (3 RQD) Three tiny FH screws for the plates.20.4 PIR Eppley Labs PIR, standard model. Assembly with shade plates.20.4.1 PIR SENSORPIR SENSORPIR SENSOR Basic PIR instrument from Eppley20.3.2 SHADE PLATESHADE PLATESHADE PLATE Shade plate from Eppley. (Sae as PSP)20.3.3 SCREWS, SHADE PLATE (3 RQD)SCREWS, SHADE PLATE (3 RQD)SCREWS, SHADE PLATE (3 RQD)SCREWS, SHADE PLATE (3 RQD)SCREWS, SHADE PLATE (3 RQD) Three tiny FH screws for the plates.20.5 HOUSING, RAD CIRCUITHOUSING, RAD CIRCUITHOUSING, RAD CIRCUITHOUSING, RAD CIRCUITHOUSING, RAD CIRCUITHOUSING, RAD CIRCUIT Complete RAD assembly.20.5.1 ROSE BOXROSE BOXROSE BOX Rose-Bopla box with connector holes.20.5.1.1 BOX, BLANKBOX, BLANKBOX, BLANK Blank box from Rose Bopla20.5.1.2 PLATE, INTERNAL, PLATE, INTERNAL, PLATE, INTERNAL, PLATE, INTERNAL, Mounting plate from Rose Bopla20.5.1.3 SCREWS, GROUNDINGSCREWS, GROUNDINGSCREWS, GROUNDINGSCREWS, GROUNDING Cu screws fro R-B (4)20.5.1.4 JOB, MACHINE, RECEP HOLESJOB, MACHINE, RECEP HOLESJOB, MACHINE, RECEP HOLESJOB, MACHINE, RECEP HOLES Drill and tap for receptacles. Machine shop job.20.5.2 CIRCUIT BOARD, COMPLETE ASSYCIRCUIT BOARD, COMPLETE ASSYCIRCUIT BOARD, COMPLETE ASSYCIRCUIT BOARD, COMPLETE ASSYCIRCUIT BOARD, COMPLETE ASSY Complete electronic circuit board.
20.5.2.1 PCB BLANKPCB BLANKPCB BLANK Blank PCB.20.5.2.2 SCREWS, MOUNTING (8)SCREWS, MOUNTING (8)SCREWS, MOUNTING (8)SCREWS, MOUNTING (8) #4 screws for standoffs.20.5.2.3 STANDOFF, MOUNTING (4)STANDOFF, MOUNTING (4)STANDOFF, MOUNTING (4)STANDOFF, MOUNTING (4) #4 threaded standoffs20.5.2.4 PARTS-ELECTRONIC PARTS LISTPARTS-ELECTRONIC PARTS LISTPARTS-ELECTRONIC PARTS LISTPARTS-ELECTRONIC PARTS LIST All components on the circuit board.20.5.2.5 JOB, ASSEMBLY PCBJOB, ASSEMBLY PCBJOB, ASSEMBLY PCBJOB, ASSEMBLY PCB RE or other make the RAD circuit board and confirm operation.20.5.3 RECEP, PSPRECEP, PSPRECEP, PSP Bulkhead receptacle and PCB connector.20.5.3.1 BHR ImpulseBHR ImpulseBHR Impulse Impulse MCBH-4-FS(SS) (with o-ring)20.5.3.2 Nut, backingNut, backingNut, backing Impulse nut for backing the recepticle.20.5.3.3 Connector, AmpModu Connector, AmpModu Connector, AmpModu Connector, AmpModu Connection to RAD PCB, 2x4, Digikey A25832-nd, AMP 87977-2
(Mates w A26711-ND, 103168-2)20.5.3.4 JOB, MAKE INPUT CABLEJOB, MAKE INPUT CABLEJOB, MAKE INPUT CABLEJOB, MAKE INPUT CABLE Make the cable for both PIR and PSP inputs to one AmpModu20.5.4 RECEP, PIRRECEP, PIRRECEP, PIR Bulkhead receptacle and PCB connector.20.5.4.1 BHR Impulse BHR Impulse BHR Impulse Merge wires to 20532. MCBH-8-FS(SS) w o-ring
PSP & PIR are on the same AmpModu connector.20.5.4.2 Nut, BackingNut, BackingNut, Backing Impulse nut for backing the recepticle.20.5.5 RECEP, PWR/COMRECEP, PWR/COMRECEP, PWR/COMRECEP, PWR/COMRECEP, PWR/COM Impulse bulkhead receptacle20.5.5.1 BHR, ImpulseBHR, ImpulseBHR, Impulse Impulse Power and communication. MCBH-6-FS(SS) w o-ring20.5.5.2 Nut, BackingNut, BackingNut, Backing Impulse nut for backing the recepticle.20.5.5.3 Connector, AmpModuConnector, AmpModuConnector, AmpModuConnector, AmpModu Connection to pwr/comm, AmpModu 2x5, Digikey A25834-ND, AMP
87977-3 (MATES W A26714-ND, 103168-3)20.5.5.4 JOB, MAKE CABLEJOB, MAKE CABLEJOB, MAKE CABLEJOB, MAKE CABLE Make the power & coms cable.20.6 CABLE SET, RADCABLE SET, RADCABLE SET, RADCABLE SET, RAD Set of cables for the RAD assembly20.6.1 CABLE, RAD TO PSPCABLE, RAD TO PSPCABLE, RAD TO PSPCABLE, RAD TO PSPCABLE, RAD TO PSP Impulse to Amphenol for PSP20.6.1.1 CABLE, IMPULSE, PIGTAILCABLE, IMPULSE, PIGTAILCABLE, IMPULSE, PIGTAILCABLE, IMPULSE, PIGTAIL Impulse plug on one end and an Amhenol will be mated n the other.20.6.1.2 CONNECTOR, AMPHENOLCONNECTOR, AMPHENOLCONNECTOR, AMPHENOLCONNECTOR, AMPHENOL We get these from Eppley with the radiometer order.20.6.1.3 JOB, ASSEMBLE PSP CABLEJOB, ASSEMBLE PSP CABLEJOB, ASSEMBLE PSP CABLEJOB, ASSEMBLE PSP CABLE20.6.2 CABLE, RAD TO PIRCABLE, RAD TO PIRCABLE, RAD TO PIRCABLE, RAD TO PIRCABLE, RAD TO PIR Impulse to Amphenol for PIR20.6.2.1 CABLE, IMPULES, PIGTAILCABLE, IMPULES, PIGTAILCABLE, IMPULES, PIGTAILCABLE, IMPULES, PIGTAIL20.6.2.2 CONNECTOR, AMPHENOLCONNECTOR, AMPHENOLCONNECTOR, AMPHENOLCONNECTOR, AMPHENOL20.6.2.3 JOB, ASSEMBLE PIR CABLEJOB, ASSEMBLE PIR CABLEJOB, ASSEMBLE PIR CABLEJOB, ASSEMBLE PIR CABLE20.6.3 POWER/COMMS CABLE -- TYPICALPOWER/COMMS CABLE -- TYPICALPOWER/COMMS CABLE -- TYPICALPOWER/COMMS CABLE -- TYPICALPOWER/COMMS CABLE -- TYPICAL Impulse plug to open pigtail, 10 m, typical for any application.20.6.3.1 CABLE, PWR COMS, IMPULSECABLE, PWR COMS, IMPULSECABLE, PWR COMS, IMPULSECABLE, PWR COMS, IMPULSE20.7 RAD BACK PLATE ASSYRAD BACK PLATE ASSYRAD BACK PLATE ASSYRAD BACK PLATE ASSYRAD BACK PLATE ASSYRAD BACK PLATE ASSY Assembly for mounting the RAD box onto the pole.20.7.1 BACK PLATEBACK PLATEBACK PLATE Blank plate with holes, ground nut, 20.7.2 HARDWARE, BOX MOUNT (4 SETS)HARDWARE, BOX MOUNT (4 SETS)HARDWARE, BOX MOUNT (4 SETS)HARDWARE, BOX MOUNT (4 SETS)HARDWARE, BOX MOUNT (4 SETS) Hardware with insulators, nuts, etc.20.7.3 HARDWARE, POLE MOUNTHARDWARE, POLE MOUNTHARDWARE, POLE MOUNTHARDWARE, POLE MOUNTHARDWARE, POLE MOUNT Hardware to bolt the plate to the pipe. Incl. ground straps.20.8 RAD PIPE STANDRAD PIPE STANDRAD PIPE STANDRAD PIPE STAND30 GPSGPS Complete GPS assembly -- See RAD Spreadsheet30.1 ZA005 GPS UNITGPS UNITGPS UNIT Garmin GPS17X unit.30.2 PIPE MOUNTPIPE MOUNTPIPE MOUNT Assembly to mount the GPS on a ship rail.40 Not used WXT ASSYWXT ASSYWXT ASSY Weather system complete assembly.40,1 WXT SENSORWXT SENSORWXT SENSOR Vaisala WXT40.2 MOUNTING ASSEMBLYMOUNTING ASSEMBLYMOUNTING ASSEMBLYMOUNTING ASSEMBLYMOUNTING ASSEMBLY Assembly to mount the WXT to a ship rail.
50 DAQ ASSEMBLYDAQ ASSEMBLYDAQ ASSEMBLYDAQ ASSEMBLY Complete data collection and software system50.1 LAPTOP & SOFTWARELAPTOP & SOFTWARELAPTOP & SOFTWARELAPTOP & SOFTWARELAPTOP & SOFTWARE Laptop assembly.50.1.1 4A003 LAPTOP PCLAPTOP PCLAPTOP PC Laptop -- Linux, Kermit, Expect, (Possibly a Mac block)50.2 3A226 POWER SUPPLY, 16 VDCPOWER SUPPLY, 16 VDCPOWER SUPPLY, 16 VDCPOWER SUPPLY, 16 VDCPOWER SUPPLY, 16 VDC Regulated power supply. 0-20 VDC, 4 A50.3 cfe ETHERNET SWITCHETHERNET SWITCHETHERNET SWITCHETHERNET SWITCHETHERNET SWITCH Ethernet switch for interface to multiports and AMF system.
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C RSR Circuit board and schematics
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D PRP Software Overview
FRSR.c Software written in C for the Onset TT8 microcoputer in the FRSR control-DataUnit (CDU)
RAD.c C program written for the AVR microcomputer in the RAD circuit.
G Expect program to coordinate raw input and averaging programs as well as systemcontrol. A kermit connection to the RSR, RAD, GPS, and TCM is established.Raw data strings are received and passed to the appropriate averaging program(avgrsr.pl,avgrad.pl,avggps.pl,avgtcm.pl). average strings from the programsare received and recorded in the data.
avggps.pl Perl program that takes raw data strings from the GPS, NMEA format GPRMC,and performs scalar and vector averaging of latitude, longitude, speed over ground,course over ground and magnetic variation.
avgtcm.pl Perl program that takes raw data strings from the Precision Navigation Inc. Tilt-Compass circuit (TCM) and performs scalar and vector averaging of pitch, roll,compass, and X,Y,Z magnetic fields..
avgrad.pl Perl program that takes raw data strings from the RAD and performs scalar averag-ing of short and longwave irradiance, case and dome temperatures, and engineeringmeasurements.
avgrsr.pl Perl program that takes raw data coded strings from the FRSR, decodes the bin-hexascii string and averages data from each sweep bin.
AOD.pl Perl program that routinely checks the averaged data files in the data folder and ifconditions are good will calculate the atmospheric optical depth (AOD) and storethe computations on a data file.
term to gps.ex Establishes a Kermit serial connection via the PDS752 hub directly to the GPS.
term to rad.ex Establishes a Kermit serial connection via the PDS752 hub directly to the RAD.
term to tcm.ex Establishes a Kermit serial connection via the PDS752 hub directly to the tilt-compass sensor, TCM.
term to rsr.ex Establishes a Kermit serial connection via the PDS752 hub directly to the FRSR.
D.1 What/Where are the data files?
BASHRC -- The file ~/.bashrc explains a lot.
less ~/.bashrc
and you will see ’prppath’ which defines the location of the prp2 software.
The variable ’SetUp’ defines the setup file. This is important.
Also you will see many useful aliases (which might need some adjustment).
gtprp -- sends you to the prp2 software folder.
PRP -- runs the data collection program and points to the SetUp file.
SETUP FILE
less $prppath/$SetUp
opens the setup file for viewing.
The data folder is defined there as "$prppath/data"
To view the data files enter
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ls $prppath/data
where you will see files with names such as
gps100821.dat -- 2-min averages of gps position
gps100821.hdr -- describes the dat file
gps100821.raw -- raw sweep gps data
rad100901.dat -- 2-min averaged radiometer data
rad100901.hdr -- describes the dat file
rad100901.raw -- raw (10-sec) data from the RAD.
rsr100901.dat -- 2-min averages fro RSR
rsr100901.hdr -- describes the dat file
rsr100901.raw -- raw (~6 sec) rsr sweep data (binhex)
tcm100901.dat -- 2-min data from the TCM (pitch, roll, fg compass, temp)
tcm100901.hdr -- describes the dat file
tcm100901.raw -- raw data from the TCM FG compass.
G100903113232.info -- run info, created at the start of the PRP command.
aod100831.da1 -- 2-min computations of solar components and aod.
aod100831.da2 -- 2-min computations of solar components and aod.
aod100831.da3 -- 2-min computations of solar components and aod.
aod100831.da4 -- 2-min computations of solar components and aod.
aod100831.da5 -- 2-min computations of solar components and aod.
aod100831.da6 -- 2-min computations of solar components and aod.
aod100831.da7 -- 2-min computations of solar components and aod.
aod100903.hdr -- info on computation of the aod files.
D.2 Direct Connections: RSR, RAD, GPS, TCM
D.3 PRP: Expect script for system integration
D.4 AOD: Compute aerosol optical depth
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E Procedures
E.1 Changing IP Addresses
E.2 Cold Weather Standby
E.3 RSR Standby
E.4 RSR Motor Assembly Maintenance
E.5 Cleaning the Radiometers
Figure 18: A PSP from a ship in the Carribean after a sand stormfrom the Sahara.
E.6 Connector Care and Maintenance
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F GLOSSARY
PRP: The complete assemblage of all the components listed below is called the Portable Radia-tion Package. The system that is described in this manual uses independent components that arelinked with a common ethernet hub. This is a new design, hence it is often designated the PRP2.More. . .
CDU: The Control Data Unit is the sealed gray box that is located with the equipment. More. . .
RSR: The rotating shadowband radiometer is the combination of motor, shadowband, nadirswitch, and control microcomputer (located in the CDU) that is used to estimate the aerosoloptical depth. More. . .
TCM: The tilt-compass sensor is a flux-gate compass with tilt compensation. It is located inthe small waterproof box on the mounting plate of the RSR. More. . .
GPS: The Geographical Positioning System is a Garmin GPS17x. It is programmed to producethe NMEA ‘GPRMC’ sentence each five seconds.
RAD: The Radiation Analog to Digital interface converts the millivolt signals from the EppleyPSP and PIR sensors to digital measurements of shortwave and longwave downwelling irradiance,SW and LW respectively. More. . .
DAQ: The Data AcQuisition computer takes data from the components above, stores raw andaveraged (2-minute) data, and computes the aerosol optical depth (AOD) which is a primarypurpose of the PRP instrument. More. . .
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G Grounding, RFI, and Noise Suppression
Grounding is a black art. The purpose of careful grounding is two-fold. First, the equipmentmust be protected from damaging electric ARCS (lightning) and inadvertent surges or drop outin the local power. Secondly, the electronic amplifiers and converters must be shielded from localelectronic or magnetic fields to reduce electronic noise in the measurements. This section willdescribe basic principles and practices to use and it will give a means of verifying that noisecontamination is a minimum. But it is essential to know that improper grounding can destroy thedata, the instrument, or both.
Figure 19: Typical grounding to the ship superstructure.
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G.1 Grounding between components
Each connector into the Control Data Unit is protected from electric discharge with tranzorbshunts. Special circuit boards are fitted over each connector so each pin is shunted directly tocase ground. Also, capacitors and ferrite beads protect each line from external radio frequencyinterference (RFI).
The electronic circuit boards maintain a strict distinction between analog ground, digital ground,and case ground (or earth). Only a single connection occurs between analog and digital ground,and inside each electronic box, only a single connection occurs between the electronic ground andcase. All RFI protection circuits are connected to case at a single point.
All external cables are shielded and all maintain a constant connection between the shield and theelectronic case grounds. The only exception to this is the FRSR head. Therefore, the FRSR headcable shield is not connected to the case at the head. This prevents groound loops.
To be absolutely sure that the case (earth) ground is continuous throughout the entire system, agrounding cable must be connected between the plate, CDU, UPS, and then to the ship superstruc-ture. If necessary, scrape the paint off of the ship superstructure to be sure the earth connectionis good.
Use a digital multimeter to measure the resistance between all components. Especially makesure the FRSR head case is common with the ground cable. The resistance between allcomponents, including the FRSR head and the preamp box, should be less than oneohm.
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G.2 How do I know the system is properly grounded?
The data collection program, PRPRX, displays the one-minute mean and the standard deviationfor the Fast Rotating Shadowband Radiometer measurements for each channel. The FRSR dataare displayed in millivolts. The global measurements are the mean of the first and last ten in-stantaneous analog-to-digital converter readings in each sweep. These represent approximately14 milliseconds when the shadowband is at each horizon. The displayed data are the mean andstandard deviation of the global data points. On a clear day with bright sun, the global meanswill be on the order of 2000-3000 mv and the standard deviations will be on the order of 5 mv.If there are grounding problems, the standard deviation will be much larger, on the order of 100mV. When you see this, the grounding must be investigated carefully.
The best figure for noise is to go to the test menu and use the “a¡return¿” command to beginmeasuring the 12-bit ADC, the FRSR head channels. The display will scroll up the screen. Waituntil about 20 measurements are taken, then press the ¡return¿ key. The mean and standarddeviation for each channel will be displayed. On a bright, clear day, with the sun overhead theradiation will be very steady and the standard deviations will be on the order of 10-20 mV. If theyare much greater, then a better grounding might help reduce them.
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G.3 Other grounding schemes
If the standard grounding scheme, outlined on the previous page, does not yield low noise condi-tions, some other grounding scheme might be in order. Local conditions might require a differentscheme in order to root out ground loops or to properly shield magnetic interference.
1. Single-point ground to the ship.This technique was used in one application and resulted in very low noise. (1) Stop the PRP. Turnoff the power switch. Remove the power cable from the UPS power in. (2) Use rubber or insulationto isolate the pole from the ship. (3) Remove the ground strap from the ship. At this point, theresistance between the PRP and the ship is infinity. (4) Reconnect the power cable. The resistanceto the ship now should be ¡ 1 ohm. The power cable shield is grounded through the power supply.
With this technique, there is one and only one ground connection to the ship and this is at the ACpower supply.
G.4 Grounding and handling the FRSR head
1. Be sure the head is always well grounded.2. Never connect or disconnect the head while the PRP is powered.3. When installing or removing the FRSR head, wear a wrist grounding strap.4. When removing the head, place it directly into a conductive bag.
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