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MITRASTransmissometer

Runway Visual Range

Advanced Training Material

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Contents

Mitras Overview

System description

RVR assessmentFunctional Description

Operating principle

Mitras VisibilityCalculation

Hardware

LM11

Installation

Operation

Communication

Commands

Troubleshooting

Maintenance

Periodic Maintenance

Operational Check

Calibration andLinearization Check

Aligning Optics

Replacing a Subassembly

HANDS-ONHANDS-ON exercises

Commands and communication

Maintenance

Troubleshooting and repair

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MITRAS Transmissometer

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MITRAS System

Conforms to all ICAO and WMO requirements for RVRand Meteorological Optical Range (MOR)

Accurate RVR assessment is a result of accurate MORmeasurement => reduces airport down-time

Improved accuracy with fully automatic measurementand unique contamination control with compensation(longer maintenance interval)

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Single Baseline System

Double Baseline System

LIGHT TRANSMITTERLIGHT RECEIVER

LIGHT TRANSMITTER LIGHT RECEIVER

LIGHT RECEIVER

Light transmitter and Light receiver

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Double baseline for CAT IIIB

Double baseline for CAT IIIB is implemented by means oftwo different beams from one transmitter.

The assessment of visibility ranges from 2/3 times theshort baseline up to 50 times long baseline.

With 10m and 200m base lines visibility from 7m upto 10 000m.

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Definition of MOR

MOR can be measured by measuring the attenuation of light

attenuation is mainly caused by scattering, to a smalldegree also by absorption (in smoke, dust, )

100 %intensity 5 %intensity

MOR

MOR is defined as the distance where the intensity of a light

beam has been attenuated to 5% of the original intensity

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What is Runway Visual Range?

Runway Visual Range (RVR) = Range over which the pilot on thecenter line of the runway can see:

- Runway markings, or- Edge lights of the runway, or- Center line lights.

RVR is not an observation nor a measurement.

RVR assessment calculation follows Allards law which takes intoaccount:

- Visibility (m)- Background luminance (cd/m2)- Airfield lighting intensity percentage- Airfield lighting characteristics (cd)

For RVR calculations 5 m is used as the average eye level of a pilot inan aircraft.

Traditionally RVR has been assessed by counting edge light lamps bythe runway. The lamps are at 60 m distance from each other. At CAT Iairport at least 14 lamps should be seen and 7 lamps at CAT II airport.

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RVR Assessment

MOR (Visibility)

MITRAS

Backgroundluminance (LM11)

=> Illuminationtreshold

Runway lightsetting

RVR Calculation

MIDAS IVRVR value

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GATEGORY DECISION HEIGHT RVR

CAT I 60 m (200 ft) 550 m or vis. 800m

CAT II 30 m (100 ft) 350 m

CAT IIIA

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Assessment of Runway Visual Range 2/3

Take-off limits in all categories (from ICAO / DOC9365, 2nd edition 1991)

Commonly acceptable take-off minima is 175m. When the facilities are: runway edge ligths, runway centre line

ligths, centre line markings and touchdown, mid-point (ifmissing 350m) and stop-end RVR.

Otherwise take-off minima is 500m. When the facilities are: runway edge ligths and either centre line

ligths or centre line markings.

VFR flights (VFR = Visual Flight Rules) require (Annex 2, 9thedition 1990)

visibility > 5000 m

clouds > 450 m

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RVR / Visibility instrumentation for different airportcategories are summarized in table.

At CAT II and III the RVR instrumentation isrequirement and at CAT I recommendation (Annex 3,14thEdition July2001).

Assessment of Runway Visual Range 3/3

CAT I CAT II CAT IIIA CAT IIIB CAT IIIC

RV lights edge edge+center as CAT II as CAT II + TWY as CAT IIIB

Instruments 1 2-3 3 3 3

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Annex 3, 14thEdition July2001:

Reporting steps of 25 m, when RVR < 400 m

Reporting steps of 50 m, when 400 RVR 800 m

Reporting steps of 100 m, when > 800 m

Visibility rounded down to steps in METAR:

50 m, when visibility < 800 m

100 m, when visibility between 800 m and 5000 1000 m, when visibility between 5000 m and 10000

reported as 10km when visibility is 10 km and over exceptwhen the conditions for the use of CAVOK apply.

Reporting steps

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R U N W A YR U N W A YR U N W A Y

ATC/TOWER

Digital display

M

M

RVR Computer and

accessories

MIDAS IV: Small system

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R U N W A Y

CEILOMETER

CT25K

0...25000 ft

Precipitation

Geonor

R U N W A Y

RWY TEMPRWY TEMPRWY TEMP

RWY TEMP RWY TEMP RWY TEMP

WINDS

PTU

PTU

WINDS

MIDAS IV: Large system

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MAINTENANCE

WORKSTATION

(RCM)

OBSERVER

WORKSTATION

(OWS)

CENTRAL DATA

UNITS (CDUs)

FIELD SENSORS

FORECASTER

WORKSTATION

(FWS)

WEATHER VIEW

WORKSTATION

(WV)

SWITCH OVER

UNIT

DATABASE

SERVER

UPS

DIGITAL

DISPLAYS

AFTN

INTERFACE

SERIAL

OUTPUT

RUNWAYLIGHT

SETTING

RVR_08

ZCZC.. METAR ENGM ...

1% 3% 10% 30%

LOCAL AREA NETWORK

ATIS

MIDAS IV: Large system

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MITRAS Operating Principle

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Measurement principle (1)

Light source

- Xenon flashlamp

- Represents the spectrums of sunlight and runway lights

- Very stable, expected lifetime 55000 h

- Light intensity can be controlled

Benefits of reference measurement (transmitted intensity)- Short-term long-term variations are compensated

very accurately

- Transmissometer stability better than 0.3%

- Unusual situation detected immediately

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Optics of MITRAS Transmissometer

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Measurement principle (2)

Averaging time

- Normal operation 30 s or 60 s

- In alignment mode 15 s

Pulse measurement principle

- Light pulse duration 1.5 s (half-width)

- Continuous light doesnt interfere: A 75000W lamp at 30 m

distance has no influence Representative spectral response

- Green optical filters are used to approximate the specralresponse of the human eye

Economy mode The flashing interval automatically changes according to the

visibility.

M i l d

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Measurement interval andnormal/economy mode

Transmissometer measures the transmittance between theLight Transmitter LP11 and Light Receiver LR11. It calculatesthe moving average over 60 or 30 samples.

In normal mode it measures transmittance every second. In economy mode it automatically changes the flashing

interval according to the visibility.

Visibility (MOR) Flashing interval

under 2 km 1 s

2 km

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LP11 / LR11 Block Diagram

Comparison of Performance

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Comparison of PerformanceTransmissometer vs. Forward Scattering

TRANSMISSOMETER

- large sample volume- limited dynamic range

- accuracy maintained in all types of precipitation- tedious installation- continuous maintenance and calibration

FORWARD SCATTERING

- small sample volume- large dynamic range

- precipitation may cause inaccurate results (unless the measurement is compensated)- easy installation- less maintenance

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MITRAS Visibility Calculations

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Meteorological Optical Range (MOR) has been defined by

the WMO as the basic parameter to express the optical state

of the atmosphere

MOR corresponds closely with human visibility

observations (day observations)

MOR has been defined as a purely physical quantity

objective

it can be measured

Visibility & MOR

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100 %intensity

5 %intensity

MOR

MOR can be measured by measuring the attenuation of light attenuation is caused by scattering and absorption

Definition of MOR

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Attenuation of Light

Law of Bouguer- Lambert:

F F ex

=

0

Definition of MOR by WMO

MOR can be calculated from extinction coefficient

F = flux of light (at distance x)

Fo = original flux of light (x = 0)

x = distance = extinction coefficient (= a + b)

where a = absorption coefficient

b = scattering coefficient

F/F0 = 5% = 0.05

F/F0 = e-x0.05 = e-x

3ln(0.05)

-=MORx =

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Attenuation of Light

Light fog

Heavyfog (large )

Clear (small )

Fog

Distance x

Light

flux

F0= 100%

F = 5%

F= F0e- x

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35 m 50 m 75 m 100 m

Transmittance Visibilities (m) at different baselines

0.995 20.947 29.925 44.887 59.8500.990 10.447 14.925 22.387 29.8500.950 2.047 2.924 4.387 5.8490.930 1.447 2.067 3.100 4.1340.900 997 1.424 2.135 2.8470.800 470 672 1.008 1.3440.600 206 294 440 5870.400 115 164 246 3270.200 65 93 140 1860.100 46 65 98 1300.015 25 36 54 71

Meteorological Optical Range (MOR)

MOR = - 3 x Baseline

ln (Transmittance)

Baseline

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Visibility Calculation

LPC11 software calculates visibility with Koschmieders law.

ICAO has defined the extinction coefficient to be 0.05 which has beentaken into account in the following Koschmieders visibility (MOR)formula:

Mitras transmissometer system uses LPI11 Light Intensity measurement units in

LP11 and LR11 for measuring light.

When calculating the visibility the software takes into account intensities with and

without contamination calculation. If Contaminantion Compensation Mode is ON

MITRAS transmits the compensated visibility to RVR Computer.

If the LPI11 boards are unlinear the software takes that into account. (The

linearization correction is made by techicians).

Where Transmittance = K1 Received light intensity = K1 R (I)

Transmitted light intensity TM (I)

and K1 is set by technicians during good visibility

Visibility = - 3 x Baseline ln (Transmittance)

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Visibility Measuring Range

Single Baseline Systems

Baseline MOR range RVR range(at night)

35 m 25....1500 m 100....1500 m

50 m 40....2000 m 150....2000 m

75 m 50....3000 m 200....3000 m

100 m 70....4000 m 300....4000 m

200 m 70..10000 m 300..10000 m

Double Baseline Systems

Baseline MOR range RVR range

10 and 75 m 7....3000 m 40....3000 m

10 and 200 m 7..10000 m 40..10000 m

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Calculations

Transmittance calculation

Transmittance is the relationship between the received and transmitted light power. The transmitted light pulseintensity is measured for every pulse by the transmitter and the corresponding received power by the receiverelectronics. The transmitter asks for the received intensity and sends the flash intensity.Thus, both the receiver and the transmitter can perform the same calculations.

Because of the electronics the scaling of the light intensity meter is not the same in the receiver and in thetransmitter. Therefore, at least linear scaling is needed to convert the intensity relation to a transmittance value.Besides linearization, scaling is sometimes needed to compensate the non-linearities in the measuringelectronics. These scaling factors are defined in the calibration procedure. Two calibration points are included inthe calculation. I.e. three linear scales are used to estimate the transmissometer response.An additional scale (K1) is used to adjust the original lines.The calibrated linear scales are called K2, K3 and K4.

During every measurement cycle, the "raw transmittance" is calculated as follows:

RAWinst = (R(I)-R(offset)) / (TM(I)-TM(offset)),

T(RAW) = AVE(RAWinst(30)) or AVE(RAWinst(60))

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Calculations

Visibility calculation, non-compensated

The Meteorological Optical Range, MOR or the visibility V is calculated using a contrast threshold 0.05recommended by the ICAO and the WMO.

where B = the effective transmissometer baseline

T ( NOC ) = non-compensated transmittance

Contamination compensated visibility calculation

For the contamination compensated transmittance correction factors TM(WT) (transmitter window) and R(WT)(receiver window) are needed.

where R(WT) can be the transmittance correction of either long or short baseline receiver window.

3 x B

-ln T( NOC )V =

T( NOC)

TM( WT) x R( WT)T ( COM ) =

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Calculations

Transmittance calculation

These instant values are collected in a 60 location rotating buffer.The latest 30 or 60 samples are used to calculate the average value T(RAW).The two lowest and two highest sample values are excluded from the average.The purpose of the correction is to filter out extreme instant transmittance values,

for instance a bird's flight through the optical path.

T(AVE) = K1*K1A*(K2,K3,K4*RAW)

The autocalibration feature uses the scaling parameter K1A initiated to 1.00 by the CAL command.If then the visibility estimation has been too optimistic, i.e. one minute average of the measured transmittance

exceeds 0.998, K1A reduces from 1.00. K1A is calculated as 0.998/measured transmittance.If K1A < 0.95, the CALIBRATION FAILURE bit is set in the status.However, the calculated correction is used.

K2 is used below the lower calibration point (P1), K3 between the calibration points and K4 above the highercalibration point (P2).

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Calculations

Contamination compensated visibility calculation

Contamination compensated visibility V ( COM ) is calculated by using the T ( COM ) :

The contamination compensated visibility is sent to the data processing unit, when

- the contamination compensation mode is ON

- the window transmittance is better than 0,92 (user selectable) for light receiver window and 0,92 for light transmitter window (compared with clean windows). When transmittances of the windows are

lower than these values, the windows are considered dirty.

The non-compensated visibility value is sent to the data processing unit, when

- the contamination compensation mode is OFF

- the contamination compensated visibility value is not available.

Contamination compensation calculations

The contamination signal is measured every 10 seconds and average of six latest samples ( one minute ) is usedin the contamination calculation. The MES 4 tables are updated every minute with these one minute values.

The scaling is initiated with the CLEAN command after cleaning the windows.

3x B

- lnT (COM)V ( COM ) =

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RVR Computer Calculations

RVR Computer calculates RVR data every 15 s. It pollsMITRAS transmissometers for visibility, backgroundluminance and status data. It receives runway light

percentage data from the interface unit or uses manuallyinput value. It has the characteristics of airfield lights inits memory.

When calculating the RVR the RVR Computer takes into

account marked discontinuity. It calculates instant RVRand following 10 minute values: average, one-minuteminimum and one-minute maximum.

It compares last 5 minute RVR values to those for 5 to 10

minutes earlier and calculates tendency (U=up, D=downand N=neutral).

RVR C C l l i

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RVR Computer Calculations

MIDAS IV RVR compoter transmits RVR values to theDD50 digital displays, printers and operators display.

The transmission to the DD50 includes instant RVR dataand the 1 and 10 minute RVR values with following rules:

- average if the one-minute minimum and maximum doesdiffers from the average RVR less than 20% or is

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Hardware

LP11 Bl k Di

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LP11 Block Diagram

LR11 Bl k Di

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LR11 Block Diagram

LPC11 Transmissometer CPU

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LPC11 Transmissometer CPU

LPC11 has

- Intel 8031 CPU chip with 7 MHz clock, 512 kb EPROM, 64 kb RAMmaintenance terminal line.

- DUART for modem line (DMX21), current loop (LPT11), frequencycounting (LMB11), peak reset and power error control.

- Analog multiplexer and 12 A/D converter.

- D/A converter.

LPC11 is used in Light Transmitter LP11 andLight Receiver LR11

- same software

- different jumper setting

Blinking LEDs indicate as follows:- Green LED blinking at 1 s interval (normal).

- Red LED indicates Reset, or an error found by star up self-test, orwatchdog circuit has given a hardware reset.

- Yellow LED blinks when LPC11 triggers the flash lamp to flash.

LPC11 Processor Block Diagram

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LPC11 Processor Block Diagram

LPC11 Jumper Setting

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LPC11 Jumper Setting

LPC11 Software v3 27 operation

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LPC11 Software v3.27 operation

LPC11 Software v3.27 is used in Light Transmitter LP11 andLight Receiver LR11.

- same software operates for single and double baseline systems- different jumper setting at LP11 and LR11 CPU boards

Software has following modules:- Built in startup tests

- Measurement of transmitted and received light intensity

- Visibility calculation and contamination compensation calculation

- Message generation

- Communication between LP11 and LR11, LP11 and RVRComputer, LP11/LR11 and maintenance terminal

- Contamination signal measurement, calculation and warning

- Monitoring temperature, flash lamp intensity and contaminationsignals

- Warning generation if monitored signals are not within limits

- Setting reference signal levels when the optics has been cleaned

LPF11 Flash Control Unit

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LPF11 Flash Control Unit

The inputs are High voltage (750 VAC) and logic signals:

- triggering pulse for Xenon flash lamp

- flash voltage signal for controlling high voltage

Intensity control with Flash Gain, charged energyE = CU where C = capacitance and

U = charging high voltage (300-800 V)

Xenon flash lamp is a stable light source. Light pulse duration

is 1.5 micro sec. The arc is bored between 2 electrodes mounted inside a glass

bulb.

Triggering socket is a potted assembly. It is connected to the

Flash Control Unit with 4 leads. Flashing interval is 1 s normal mode and in economy mode

1 s to 10 s.

LPF11 Circuit Diagram

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LPF11 Circuit Diagram

LPH11 Heating Control Board

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LPH11 Heating Control Board

Controls the heating of the internal optics and protectionwindow.

The electronics of optics operates best in stable

temperature. The operating temperature range is definedwith a jumper on the LPH11.

The heating of protection windows prevents surfacesfrom condensating water.

The green led light shows that window heating is on.

LPH11 Circuit Diagram

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LPH11 Circuit Diagram

LPH 11 Jumper Setting

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LPH 11 Jumper Setting

Contamination Detector

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Contamination Detector

DMX21 FSK Modem

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DMX21 FSK Modem

MITRAS communicates to the RVR Computer via 300 bpsleased modem line. Line speed 300 bps, Even parity, 7 data bits and 1 stop bit

The DMX21 operates in ANSWER mode and its switchesshould be Up, Middle and Down.

The LEDs indicate polling (RXD), answering (TXD), and Carrierdetected.

Troubleshooting - Cover theLEDs with hands in order to see how the LEDs are blinking.

- Check that RXD LEDblinks every 15 s when RVRComputer polls

it and the MITRASanswers with longer message (TXD LEDs blink).- Check that the green LED on the LPC11 CPU board blinks every

second. If not reset the MITRAS light transmitter LP11.

- Turn off power. Remowe the DMX21 and check the jumper

setting. Restart the LP11 again.- Check cables and their connections.

13100LP Cabling Diagram

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13100LP Cabling Diagram

12930LP Wiring Diagram

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g g

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LM11 Background Luminance Meter

LM11 Background luminance meter

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g

Connected to the MITRAS LP11 transmitter

Measurement range: 4 30.000 cd/m2

Spectral response range: 300700 nm, peak = 550nmInternal heating to avoid condensation

Cable totransmitter

Mechanicalinterface

Tilt adustment

Optics

LM11 Background luminance meter

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g

MEASUREMENT PRINCIPLE

LM11 measures the amount of ligth coming from a 7ocone to

the 46 mm lens.incoming ligth is focused on the matte glass

matte glass will prevent from increasing the luminance

values caused by bright spotsmatte glass provides a smooth average response

The ligth spectrum is detected by PIN photodiodegreen filtered

photoelectric current is converted into frequency which

linearly corresponds to cd/m2divided by 10.

LM11 Background luminance meter

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g

Internal heating to avoid condensation

body and lens heated

monitored by two thermistors

INSTALLATION

The meter should be directed towards the North sky

Direct sunligth into meter should be avoided

The meter is normally tilted upwards to the horizontal level

at angle of 20oto 50o

Recommended installation angle of 30o

Directed sligthly above the runway ligths

Background Luminance Meter LM11

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Side view: 1 Housing2 Back plate3 Aluminium body4 Hood5 Power transistor6 Cable with connector7 Matte glass

8 Green filter9 PIN photodiode10 Lens11 Front plate12 O-ring13 Rubber gasket14 M4 screws

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Installation

Selecting location

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Transmissometers should be located in position whichensure representative measurements for intended purpose(see references from Users Guide).

Locations at airport (according to ICAO Annex 3):

CAT I runways

One transmissometer near the touchdown zone, 50mbaseline recommended

CAT II runways

Less than 2400m long: Two transmissometers

More than 2400m long: Three transmissometers

CAT III runways

Three transmissometers, double baseline systems with 10m

and 75m baselines recommended

Sensor Locations at Airport

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Transmissometer foundation recommendation

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Base plate set assembly & installation

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LP11 Cabling and earthing recommendation

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Cabling diagram for single baseline

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Service platform principal dimensions

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Communication

I/O Lines

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Output interfacesBoth the light transmitter and the light receiver have three separate serial lines which are used as follows:

Light transmitter

(Line 0) Maintenance line (CPU) RS-232C

(Line 1) to RVR computer (DUART B) modem or MITIF

(Line 2) to light receiver (DUART A) current loop

Light receiver

(Line 0) Maintenance line (CPU) RS-232C

(Line 1) Auxiliary (DUART B) (RS-232C)

(Line 2) to light transmitter (DUART A) current loop

Maintenance line

The maintenance line is used for monitoring, testing and calibration purposes. Maintenance line commands aredescribed in title "Commands".

Line parameters:

300 baud, 7 data bits, 1 stop bit, even parity

Communication protocol:

- Conversation mode, character by character

- XON/XOFF handshake

- Timeout 60 seconds

Transmissometer Message

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where

P, ID, V, B, S constant characters

X variable value

_ ASCII character 20 hex (Space)

ASCII character 0C hex (Carriage return)

ASCII character 02 hex (Start of text)

ASCII character 03 hex (End of text)

ASCII character 0A hex (Line feed)

Status of receiver 2 is set spaces if a single baseline system is used.

Status of each equipment consists of two HEX-ASCII characters.

ID_X_V_XXXXXX_B_XXXXX_SXXXXXX_

Status of receiver 2 (VI)

Status of receiver 2 (V)

Status of receiver 1 (IV)

Status of receiver 1 (III)

Status of transmitter (II)Status of transmitter (I)

Background luminance

Visibility

Transmitter ID (0...7)

Status

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Transmitter status:

BIT.0 = 1 Meas mode (0 = OFF) (1 = ON)

BIT.1 = 2 Cont/other (0 = OFF) (1 = ON)

BIT.2 = 4 Optical surface (0 = OK) (1 = DIRTY)

BIT.3 = 8 Power supply (0 = OK) (1 = FAIL)

BIT.4 = 1 Heating (0 = OK) (1 = FAIL)

BIT.5 = 2 Flash lamp (0 = OK) (1 = WEAK)

BIT.6 = 4 BL meter (0 = OFF) (1 = ON) 1)

BIT.7 = 8 Measurement loop (0 = OK) (1 = FAIL)

Receiver status:

BIT.0 = 1 Meas mode (0 = OFF) (1 = ON)

BIT.1 = 2 Cont/other (0 = OFF) (1 = FAIL)

BIT.2 = 4 Optical surface (0 = OK) (1 = DIRTY)

BIT.3 = 8 Power supply (0 = OK) (1 = FAIL)

BIT.4 = 1 Heating (0 = OK) (1 = FAIL)

BIT.5 = 2 Calibration (0 = OK) (1 = FAIL)

BIT.6 = 4 Test (0 = OK) (1 = FAIL)

BIT.7 = 8 Consistency (0 = OK) (1 = FAIL) 2)

1)ON if the background luminance (BL) meter is set on with the command MODE2)Only in double baseline system

I

II

IV

(VI)

III

(V)

Operation and Maintenance Connection

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Modem line to data processing unitNormally, the data processing unit uses this line for message polling from the MITRAS light transmitter(s) but onecan also use it for maintenance purposes similar to the MITRAS maintenance line.

Line parameters:

- 300 baud, 7 data bits, 1 stop bit, even parity

- Optional 1200 baud for RS-232 interface (Not used)

Communication protocol:

- Data packet protocol

- Data validity confirmed with character parity check

- Timeout 60 seconds

Commands

The MITRAS Transmissometer software has operator's commands for monitoring, testing and calibrating the unit.Commands can be given via both the maintenance line and the modem line,i.e. computer/auxiliary line.

NOTE: The line is automatically closed after 60 seconds, if no commands are given.

If you want to keep the maintenance line open, give a space as input. After a space mark, you can later give thecommand you want.

All commands or inputs are entered for processing by pressing ENTER or CARRIAGE RETURN. In some cases thecommand can be followed by a space and the desired parameter value(s).

OPEN Opens the line for operator commands.

OPEN for modem line.

HELP Outputs a list of commands.

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Commands

Operation and Maintenance Commands

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The transmissometer command set consists of six different types of commands:

1. Transmissometer initializing commands for start-up

- not normally used after start-up period

2. Transmissometer initializing commands for operational use

- can be used during operational use

3. Message commands

- can be used for maintenance and test purposes and also for data output

4. Mode selecting commands

- aimed at mode altering during operational use

- effects of mode selecting commands must be familiar to the operator

before use

5. Routine maintenance commands

- used to maintain accurate operation of the transmissometer

- some of these commands require that the user is authorized to changeparameters, e.g. to calibrate according to visual observation

6. Special maintenance commands

- needed only when troubleshooting failures or when testing specialfunctions of the transmissometer.

Initializing Commands for Startup

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CONF With this command you may initialize (and set) the system parameters.Usually this command is used during installation only.

The system response to CONF command is presented below:

>CONF

CONFIGURATION STARTED 0000-00-00 00:44:51

MITRAS SOFTWARE VERSION V3.25 2000-04-19

TRANSMITTER ID 1

SINGLE BASELINE

MEAS MODE ON

ECOM MODE ON

AUTO CALIBRATION ON

JUMPER FIELD 00100000

SELECT OPERATION MODES

MEAS MODE (1=ON, 0=OFF) 1

ECON MODE (1=ON, 0=OFF) 1

CONT MODE (1=ON, 0=OFF) 1

AUTO CALIBRATION (1=ON, 0=OFF) 1

BL METER (1=ON, 0=OFF) 1

AVE COUNT (1=60, 0=30) 1

Initializing Commands for Startup cont.

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SET THE BASELINE

BASELINE 49.40

INITIALIAZE SCALING FACTORS

K1 0.5807

K2 1.0000

K3 1.0000K4 1.0000

TRANSMITTER OFFSET (mV) 0.0

RECEIVER OFFSET (mV) 0.0

BACKGROUND LUMINANCE SCALE KBL 10.000

INITIALIZE CALIBRATION POINTSP 1 0.5000

P 2 0.9900

CURRENT FLASH GAIN 127

AP 24.0000

DIRTY LIMIT 0.920

CONFIGURATION END

Initializing Commands for Startup cont.

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PAR With this command all the necessary parameters, such as transmissometer scaling

factors, calibration points, baseline etc. can be reviewed at one glance by the operator.> PAR

SYSTEM PARAMETERS

TRANSMITTANCE SCALING FACTORS

K1 0.5807

K1A 1.0000

K2 1.0000

K3 1.0000

K4 1.0000

RECEIVER OFFSET (mV) 0.0

CALIBRATION POINTS P1 0.50 P2 0.99

AVERAGING 60S, CONT ON

TRANSMITTER OFFSET (mV) 0.0

BACKGROUND LUMINANCE SCALE KBL 10.000

BASELINE 49.40

FLASH GAIN 127

CONTAMINATION SCALES AP 24.0 DIRTY LIMIT 0.920

WINDOW SIGNAL SCALE 1.092

SETF Sets the flashlamp intensity, may be used for calibration and maintenance purposes.

Initializing Commands for Operational Use

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OPEN Reserves the communication line and serves as password to the system.

OPEN

In modem line multiple transmissometers are separately connected to the line, when

the operator is using the OPEN mode. Only the unit with correct identification (ID)

switches the carrier on.

CLOSE Is the counterpart of the OPEN command switching the carrier off and releasing theline. Must be used as the last command when maintenance session is finished.

DATE With this command you can ask for the date or change it. To change the date,input a new date after the command as follows:

>DATE 1988 02 31.

TIME With this command you can ask for the time or change it. To change the time,

input a new time after the command: >TIME 23 45.

NOTE: The time and date are mainly for test purposes and not accurate. There is no battery

back-up either.

Initializing Commands for Operational Use cont.

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HELP Displays the transmissometer commands. Some of them are not effective in the receiver.>HELP

MITRAS TRANSMISSOMETER COMMAND SET

MES DISPLAY MESSAGE NUMBER N

PAR DISPLAY SYSTEM PARAMETERS

STATUS DISPLAY STATUS MESSAGE

CLEAN INIT CONTAMINATION MEASUREMENT

CONF INIT CONFIGURATION

CAL CALIBRATION ADJUST

FCAL TWO POINT FILTER CALIBRATION

CHECK CALIBRATION CHECK

MODE SET OPERATION MODESSETF SET FLASH LAMP GAIN

DMES RAW DATA MESSAGE

OPEN RESERVE THE COMMUNICATION LINE

CLOSE RELEASE THE COMMUNICATION LINE

ALIG ALIGNMENT HELP

TCON CONTAMINATION TEST

AMES AUTOMATIC MESSAGE

FRE BL FREQUENCY INPUT TEST

AN N ANALOG INPUT TEST, CHANNEL N

RESET RESET COMMAND

TIME

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The operator may give message commands in the form MES or in the form MES N C T, where

N is the message number; values for N are 0...5.

C is used when continuous output is desired

T is the nominal time interval between output, when certain output

interval is desired in seconds. T may range from 1 to 59 seconds.

MES 1 C 10 Gives message 1 with a 10 seconds delay between messages.

MES 0 (or MES) Output message consists of date, time, transmissometer ID, visibility,

contamination compensated visibility, background luminance and

transmissometer status:

1988-12-31 23:59:59 ID 1 V2450 CV2870 B1200 S4101

Message Commands cont.

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MES 1 Output message consists of date, time, TM(I) = light transmitter flashlamp intensity

R(I) = light intensity from long baseline receiver

T(RAW) = averaged raw transmittance value

T(NOC) = non-compensated transmittance value

V(NOC) = non-compensated visibility value

T(COM) = contamination compensated transmittance value

V(COM) = contamination compensated visibility value

DATE TIME TM(I) R(I) T(RAW) T(NOC) V(NOC) T(COM) V(COM)

1988-12-31 23:59:59 2543 3211 1.0500 0.8500 2450 0.8720 2870

MES 2 Output message consists of date, time,

TM(T) = light transmitter optics temperature

TM(C) = average of scaled transmitter contamination measurements

TM(WT) = light transmitter window transmittance

R(T) = light receiver optics temperature

R(C) = long baseline receiver contamination measurement

R(WT) = light receiver window transmittance

DATE TIME TM(T) TM(C) TM(WTP) R(T) R(C) R(WT)

1988-02-04 12:30:59 30.8 0.9500 0.9992 31.2 0.9400 0.9985

Message Commands cont.

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MES 3 Output message consists of the transmittance measurement table,

which includes the last 60 instant RAW values.The averaged output is a mean of the last 30 or 60 valuesof this table depending on the selected mode.

MES 4 Output message consists of scaled contamination measurement table(s)of both the light transmitter and the light receiver(s).The last 60 one minute instant values are displayed.

MES 5 Output message consists of visibility, compensated visibility,

background luminance and transmissometer status.

Message Commands cont.

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Certain airport systems require an automatic message sending mode. If the automatic messagemode is not used, the RVR system polls a message from Mitras.

AMES N T The AMES command defines the data message, which is sent as the

automatic message or as the default polled message. The output of the

automatic message can be seen only in normal data output (modem/MITIF),not via a maintenance line connection.

The software versions 3.22 or later include AMES command.

N Message number (0...6). Message -1 disables the automatic message.

T Message time interval (1...255 seconds). If value is not given the previous

interval setting is used.

NOTE: The default automatic message mode setting in MIDAS RVR system is

AMES 6 15

Mode Selecting Commands

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MODE With this command the operator can change the functional modes of the transmissometer.These functions are also included in the CONF command (configuration session).

The mode in question is selected simply by inputting 0 or 1.

The following modes and alternatives are available:

MEAS MODE 1) ON - visibility measurements are made

2) OFF - stand-by, flashlamp is not used

ECON MODE 1) ON - during good visibility flashing rate is reduced, for low visibility

automatically increased

- purpose: to save flashlamp and make continuous measurement possible

2) OFF - economy mode is not applied, flashing rate is fixed to 1 flash/second.

CONT MODE 1) ON - contamination compensation is used

2) OFF - no compensation is made

BL METER 1) ON - background luminance measurement is done

2) OFF - no background luminance measurement

AVE COUNT 1) 60 - 60 values used for transmittance averaging

2) 30 - 30 values used for transmittance averaging

AUTOCALIBRATION 1) ON - switches autocalibration on

2) OFF - no autocalibration

Routine Maintenance Commands

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HELP Displays the transmissometer commands. All of them are not effective in thelight receiver unit

STATUS Outputs both light transmitter and light receiver(s) status information. Use

only via data processing unit or at the light transmitter.

DMES DMES displays the raw data message in double baseline format.

DMES C Continues the display until ESC is pressed.

DMES C 30 Continues the display until ESC is pressed keeping a 30 seconds' delay

between messages.

DMES command output

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TM(I) RL(I) RS(I) TL(AVE) TS(AVE) V(L) V(S) BL C(TM) C(L) C(S)1317 1464 //// 0.9524 ////// 4615 ///// 840 0.9998 0.9983 /////

TM(I) = flash light intensity from the A/D converter

RL(I) = received intensity from the long baseline receiver

RS(I) = received intensity from the short baseline receiver in double baseline systems

TL(AVE) = scaled transmission without contamination compensation

TS(AVE) = as TL(AVE) but from the short baseline data

V(L) = visibility calculated from the upper limit corrected TL(NOC)

V(S) = visibility calculated from the upper limit corrected TS(NOC)

BL = background luminance value

C(TM) = scaled (clean = 1) contamination value of the transmitter window

C(L) = scaled contamination value of the long baseline receiver window

C(S) = scaled contamination value of the short baseline receiver window

Routine Maintenance Commands cont.

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CAL The final calibration and routine corrections can be done using this command. Software readjusts the K1 scale and initiates the autocalibration factor K1A. The new K1, K1A and the corresponding transmittance are displayed. K1 should now be close to value 1.0 (if FCAL is first carried out).

The system response to the CAL command is presented below.

>CAL 10000

K1(L) T(L)

0.756 0.9778

CALIBRATION DONE

CLEAN Give the CLEAN command only when it is necessary. The CLEAN command sets new

reference values for contamination measurement. The system response to the CLEAN

command is presented below.

>CLEAN

CONTAMINATION SIGNAL CALIBRATION IS DONE IN FEW MINUTES

Routine Maintenance Commands cont.

CHECK filt l

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CHECKThe calibration quality is checked with test filters and the CHECK command. The

software displays the 'target visibility' calculated from the current visibility taking into

account the attenuation caused by the filter in use. The software outputs the reached

visibility (VIS) value of each second. It calculates and displays the difference from the

filter visibility (VER) and the filtered reference transmittance (TER).

The system response to the CHECK command is presented below:

>CHECK 0.6

CALIBRATION CHECK

REF TRANSMITTANCE(S) AND CORRECT FILTER VISIBILITIES

CURRENT T, FILTER VISIBILITY

0.9766 421

VIS VER TER

436 15 0.005

CHECK END

Special Maintenance Commands

FCAL Th FCAL (filt lib ti ) d i d t d t i th li f t K2 K3 d K4 d i

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FCAL The FCAL (filter calibration) command is used to determine the scaling factors K2, K3, and K4 used inthe transmittance scaling. These factors are automatically recalculated after each filter calibration

procedure. Visibility must be stable during the sequence, which takes about five minutes. Windows

should be clean. The factors K2, K3, and K4 can be initialized to the default value 1.0 with the CONF

command. The command sequence for a double baseline system is presented below.

>FCAL

FILTER CALIBRATION

GIVE CORRECT VISIBILITY VALUE

GIVE FILTER P1 (LOW) VALUE

SET FILTER AND TYPE ESC WHEN VALUE IS STABLE

INST(L) AVE(L) INST(S) AVE(S)

0.5510 0.5511 0.5510 0.5511

GIVE FILTER P2 (HIGH) VALUE

SET FILTER AND TYPE ESC WHEN VALUE IS STABLE

INST(L) AVE(L) INST(S) AVE(S)

0.9310 0.9320 0.9110 0.9107

NEW SCALING FACTORS K2 K3 K40.9078 1.1070 0.9042

ARE THE SCALES OK ? (Y/N) Y

NEW SCALES ARE UPDATED TO EEPROM

FILTER CALIBRATION DONE

Special Maintenance Commands cont.

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TCON This command is for contamination measurement test purposes. The output includes a

direct contamination signal (stray light included), reference intensity from

contamination detector light source and scaled contamination measurement value.

> TCON CONTAMINATION MEASUREMENT TEST

SIGNAL : REF =

3908 3908 1.0000

3909 3909 1.0000

ALIG This command helps one in the alignment process during the transmissometer

installation. It displays continuously (until ESC is pressed) the maximum transmissionsince start and the difference of the latest value from the maximum. Bel-character

"beep" is echoed when a new maximum is reached.

Special Maintenance Commands cont.

The normalizing scale for this result value is calculated by the clean command

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The normalizing scale for this result value is calculated by the clean command.AN N Analog channel input test. Outputs A/D conversion result from selected channel

number N.

AN 1 Outputs continuously A/D conversion results of the light intensity measurement

channel.

AN 2 Outputs continuously A/D conversion results of the temperature measurement channel.AN 3 Outputs continuously A/D conversion results of the contamination measurement

channel.

AN 4 Outputs continuously A/D conversion results of the contamination

measurement reference channel (contamination lamp intensity).

FRE Frequency input test for background luminance meter interface. Result is output in Hz.

>FREQ

FREQUENCY INPUT

INST(1S), AVE(10S)

1020 1020

1019 1020

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Troubleshooting

Status

MES includes status bits in 4 character hexadecimal

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MES includes status bits in 4 character hexadecimalnumber for single baseline system and 6 character fordouble baseline.

Status 4101 is OK for transmissometer with Backgroundluminance meter and 0101 for others (double baseline410101 and 010101).

STA command gives status in plain language.

Status Information

The transmissometer output for STATUS command is:

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The transmissometer output for STATUS command is:

TRANSMISSOMETER STATUS

TRANSMITTER REC(L) REC(S)

MEAS MODE ON ON ON

CONT/OTHER STATUS OK OK OK

OPTICAL SURFACE OK OK OK

POWER SUPPLY OK OK OK

HEATING OK OK OK

FLASH LAMP OK

BL METER ON

MEASUREMENT LOOP OK

CONTAMIN. LAMP OK OK OK

CALIBRATION OK OK

TEMPERATURES 30.3 29.5 31.2 CONTAMINATION 0.0 0.0 0.0

MEASURED DATA

T(LONG) T(SHORT) V(L) V(S) BL C(T) C(L) C(S)

0.9523 0.9840 4608 3769 333.0 0.9998 0.9983 1.0044

Alarms Presented in Central Computer

Alarms on operator's terminal of data processing unit

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Alarms on operator s terminal of data processing unit

BLANK = Transmissometer operation is OK.

Transmissometer status

FAIL = Any of transmissometer status alarm bits may be set on, i.e. maintenance

needed.

OFF = Transmissometer measurement mode is OFF; the measurement mode can be set ON by maintenance commands.

Optical surface

DIRTY = The protective windows of the transmissometer should be cleaned.

Cleaning of the background luminance meter lens should be done at the

same time.

If the status DIRTY remains on after cleaning the windows,

check the operation of contamination compensation.

Status Information

The first eight status bits of the status message are included in the standard message sent to thedata processing unit The standard message includes 8 status bits for the light transmitter and 8

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The first eight status bits of the status message are included in the standard message sent to thedata processing unit. The standard message includes 8 status bits for the light transmitter and 8status bits for the light receiver. The CONT/OTHER FAIL is used as a common failure indicationfor status bits 9, 10, 11 etc. Only bit 9 is operative and informs on contamination lamp brightness.Status bits 10, 11, etc. are not presented, they are reserved for future use.

The status information can be analyzed by means of the following alternatives:

MEAS MODE OFF - Transmissometer is in stand-by mode.

MEAS MODE ON - Normal visibility measurement is performed.

CONT/OTHER STATUS OK - Contamination lamp intensity high enough, no failures detected.

CONT/OTHER STATUS FAIL - Contamination lamp intensity below 1000 (too low) or some other failure detected.

OPTICAL SURFACE OK - No cleaning of protective windows is needed.

OPTICAL SURFACE DIRTY - Protective windows should be cleaned.

- Transmittance is decreased with four percent per window and the visibility output is slashed.

Status Information

Transmissometer status information in detail

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The corresponding status bits in the light receiver(s) operate in the same way.There are some special status bits available only at the light receiver side:

CALIBRATION OK - No calibration error detected.

CALIBRATION FAILURE - The transmittance data is continuously 0.998 which is an

unusual situation.

- The autocalibration constant K1A is less than 0.95.

- The cause can be in the light transmitter or receiver. - If this status occurs from time to time, the optical alignment

should be checked.

Troubleshooting Hints

Hints for troubleshooting:

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POWER SUPPLY FAIL * Check the fuses on the mother board.

* Replace the LPP11 power supply unit.

HEATING FAILURE 1. Check internal temperature by the STATUS command.

2. Check the heating fuses, heating supply switch and heating voltage on the connector X7 of LPT11 (a.110 VAC).

3. Observe the length of the heating duty cycle indicated by the green LEDs on the LPH11 unit: is it reasonable concerning ambient temperature?

* If not, replace LPH11 and check the length of the heating duty cycle again. If this did not help, check the temperature voltage signal from the LPI11 output TEa.

4. If the heating duty cycle is reasonable and replacement of LPP11 (or LPI11) did not help:

* Check whether the bimetallic switch in the electronics box is conducting ( turn mains heating and supply power off and measure resistance over it, should be lower than 1 ohm ).

* Check the cables, connectors and heating elements.

Troubleshooting, cont.

Hints for troubleshooting :

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FLASHLAMP FAILURE 1. Check the TM(I), i.e. intensity of the flashlamp by the DMES or MES 1 commands,should be over 1000.

2. Check the flashlamp intensity setting values.

* Try to give a bigger value for SETF and check whether the brightness of the flashlamp increases to a sufficiently high level, for instance over 1500 is acceptable.

* If the cause for reduced intensity was aging of flashlamp, check the stability of it after giving a new SETF value, and taking TM(I) values in one hour's intervals,

at least 10 values each time.

CURRENT LOOP FAILURE 1. Give reset to the light transmitter, check the operation of the current loop by means of the green LED on the LPT11 unit.

2. Give reset to the light receiver(s).

3. Check the current loop supply voltage on the LPT11.

NOTE: More hints for troubleshooting can be found from Users Guide.

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Maintenance

Periodic Maintenance

The periodic maintenance of the transmissometers guarantees that the MITRASsystem operates within the range of its characteristics and the ICAO

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p gsystem operates within the range of its characteristics and the ICAOrecommendations.

The following table presents the recommended interval for periodic maintenance.

Maintenance Action Recommendedinterval

MaximumInterval

Operational check of

transmissometers via data

processing unit or PC

1 week 2 weeks

Cleaning of windows 1 month or asindicated

3 months

Cleaning of windows if no

contamination compensation

1 week or as

indicated

2 weeks

Alignment and calibration check 6 months (or after

wet or frostyseason)

12 months

General checking of cables,

connectors, and parts in

electronics box and optics heads,

and Backround Luminance Meter

LM11

6 months 12 months

Check After 1 Month of Operation

Stability troubleshooting during start-up period, first 6 months:At start-up after installation

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p

- Make sure that the transmissometer is not in the contamination compensation mode.

- Clean the windows.

- Check the calibration of the transmissometer.

- With PAR check thar the K1A equals 1.00.

Alignment check after one month's operation

(The main purpose is to check that the transmissometer alignment is stable.)

- Change ECONOMY mode OFF.

- Clean the windows.

- Check the upper-range value(s) by giving MES 1 C or DMES. If it has decreased 3 percent or more:

* Check that anchor bolts and frangible bolts are fixed properly.

* Realign the light transmitter and the light receiver(s).

* Check that the fixing nuts of the alignment adjustment screws are locked properly.

* Recalibrate the transmissometer.

- If the upper-range value has changed less than 3 percent, the installation of the transmissometer can be considered stable.

- Check K1A by giving PAR.

- Give CAL to rescale the transmissometer, if the upper-range value has changed more than 1 percent.

Checks After 2 Months of Operation

Stability check 2 months after installation

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- Clean the windows.

- Compare the transmissometer output transmittance values with the values you checked one month ago.

- If changes are less than 1 %, stability of the transmissometer is OK.

NOTE: Changes in visibility conditions may increase fluctuation in transmittance values. With a 75 m baseline transmissometer the output changes 1.1 % when visibility changes from 15 km up to 50 km.

- With MES 1 C check the upper range value. If changes are in the range of 1.5 %...3 %, the obtained differencies in the upper-range values may be due to visibility variations, which must be first considered. However, the checkpoint at 50 % should not change more than 1.5 %, and the checkpoints 10 %, 25 % should not change more than 1 %.

- Check that K1A is between 0.95 and 1.00.

* In case change of upper-range values is 1.5 %...3 %, repeat the stability check on the next clear day.

- If the above mentioned limits are exceeded, go through the linearization check.

Operation and Maintenance

Contamination compensation operational check

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- When stability check is passed, change the transmissometer to operate in the contamination compensation mode.

- Make a calibration check after one month's operation of contamination compensation.

- Do not clean the windows.

By STA command you can read the contamination percentage, signals and actual transmittance values.

- Save or write down the values.

- Clean now the transmitter window and see by DMES that C(T) is 0.9...1.1 and stable.

- Recheck by STA and save the values. The change of T(LONG) and T(SHORT) compared to

the change in the percentage value shall be approximately the same. - Repeat the steps for the receiver window(s).

- If the differencies are more than 1.5 %, you may calculate a new compensation power Ap:

where C = contamination signal before cleaning

T = T before/T after

NOTE: Ap = 24 is recommended to be used.

In( C)

ln (T )

Ap =

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Calibration and Linearization check

Calibration CHECK-1

1) Collect tools, filters, laptop terminal, cable, manual, cleaning liquid, unlintedcloth and ladder.

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cloth and ladder.

2) Take a copy of Calibration Sheets, visibility over 10 km and no wind overthe runway to the transmissometers.

3) Connect the Laptop PC to LP11 and start Terminal emulation-program at PC.

Check STA for status and DMES C for the outputted visibility.4) Clean optical windows of LP11, LR11 and LM11.

5) Check the current settings of the jumper (X2) from Heating Control BoardLPH11.

6) Switch the AC and heating power on both the transmitter LP11 and receiverunit(s) LR11. Inside temperature need about 30 to 60 minutes to stabilize.

7) Use STATUS command to check that transmissometer status does notindicate FAIL.

Calibration CHECK-2

8) Use MODE command to select the correct functional modes.>MODE

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MODE

SELECT OPERATION MODES

MEAS MODE (1=ON, 0=OFF) 1 1

ECON MODE (1=ON, 0=OFF) 1 0

CONT MODE (1=ON, 0=OFF) 1 0

AUTO CALIBRATION (1=ON, 0=OFF) 1 0

BL METER (1=ON, 0=OFF) 1 X

AVE COUNT (1=ON, 0=OFF) 1 1

9) Test the contamination measurement of the transmitter and receiver unit(s)with the TCON command. The SIGNAL and REF parameters must be at range1000...3500 when protective windows are clean. TCON command must begiven separately for both transmitter and receiver(s).

10) Use DMES command to verify that the scaled contamination values C(TM)and C(L) (and C(S) for short baseline) are close to 1 (0.96...1.04) when thewindows are clean. If the value is below 0.96, clean the windows againg andrepeat test. If the value is below 0.96 after several cleanings, give CLEANcommand. If the value is above 1.04, give CLEAN command.

Calibration CHECK-3

11) Use the CONF command to check that the baseline length is correct.

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) g

12) In the case the Ligth Intensity Measurement Board LPI11 of the receiver isreplaced, check that the scaling factors K1, K1A, K2, K3 and K4 are initializedcorrectly before the calibration and linearization checks are performed. Use

the CONF command to write down the previous set values. After this initialize all the scaling factors K1, K1A, K2, K3 and K4 of the

corresponding baseline(s) to 1.

13) Use DMES C command to check current visibility value V(L) (and V(S)) andcompare the value with reference visibility value. If the reference visibility

value and V(L) (and V(S)) correspond calibration is not needed.

If the V(L) is not close to reference value, give the correct MOR value with CALcommand

>CAL ie. > CAL 10000

14) Use MODE command to retreive earlier functional modes (see step 8).

Linearization CHECK-1

1) Check the calibration and visibility. If calibration needs adjustemnts do thecalibration procedure.

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2) Use MODE command to select the correct functional modes.

>MODE

3) Clean all optical surfaces as described in calibration section.

4) Use the Mitras calibrator filter set. Use the test filters 0.90, 0.50 and 0.25 andthe combination of 0.50 and 0.25 as 0.125. Clean the filters with a milddetergent and a soft, lint-free cloth.

5) Give command

> CHECK 6) Insert the test filter into the transmitter hood in such a way the filter value can

be seen from front. Wait until the VER and TER values have settled. VER is thedifference from the filter determined visibility and TER is the difference fromthe filter determined transmittance. Stop the output on the screen by pressingthe ESC key.

7) Write the FILTER, CURRENT T, VISIBILITY, VIS, VER, and TER values down tothe Calibration Sheet.

Linearization CHECK-2

8) Remove the test filter. Give the DMES C command and wait until the V(L) (andV(S)) value stabilizes back to the current visibility value without the filters.Stop the output on the screen by pressing ESC

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Stop the output on the screen by pressing ESC.

9) Repeat the steps from a to e with all the filters and filter combinations.

10) Check from the Calibration Sheet that the TER values are within the tolerance

|TER| < 0.02. If a test filter is out of tolerance, perform the check again. Smallamounts of pollution, dust, sand, or other fluctuations may cause erroneousresults. Also check that the test filters are clean and undamaged. In casefurther problems arise, contact Vaisala.

NOTE:The FCAL command should not be used without permission from Vaisala.

11) Use MODE command to retreive earlier functional modes (see step 2).

Calibration and linerization check sheet

Filter Calibration with FCAL CommandDATE INITIALS RVR ID

CORRECT VIS.

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DATE INITIALS RVR ID

FILTER CURRENT T VISIBILITY VIS VER TER OK

DATE INITIALS RVR ID

FILTER CURRENT T VISIBILITY VIS VER TER OK

DATE INITIALS RVR ID

FILTER CURRENT T VISIBILITY VIS VER TER OK

DATE INITIALS RVR ID

FILTER CURRENT T VISIBILITY VIS VER TER OK

VALUE INST (L) AVE (L) INST (S) AVE (S)

FILTER P1 (LOW)

FILTER P2 (HIGH)

NEW SCALING FACTORS K2: K3: K4:

Linearization Check with CHECK CommandThe recommended visibility tolerances are

given in the table below

MOR Visibility ( metres ) Tolerance ( metres )

< 150 25

150...500 50

500...10000 100

1000...1200 200

>1200 20 % of the reference visibility

Select filters for FCAL

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Linearize the T(NOC) with parameters K1, K2, K3 and K4.At the end K1=K1A=1 and K2, K3, K4 have new values.

Choose the two (2) filter values where the LPI11 are most unlinear. Draw Tfilter/ Toutput graphics indicating TER values

Select the filters where TER are the biggest or on the different side of linar line. If the TER of very short visibility is over 0.015 consider how many meters the visibility differs from correct- often it could be only couple of

meters.

FCAL command

FCAL Used to determine the scaling factors K2, K3 and K4 used in the transmittance scaling. These factors are recalculated automatically after FCAL procedure. See chapter 4, "Periodic maintenance", for further information. The command sequence is as follows:

FCAL

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>FCAL

FILTER CALIBRATION

GIVE CORRECT VISIBILITY VALUE

GIVE FILTER P1 (LOW) VALUE

SET FILTER AND TYPE ESC WHEN VALUE IS STABLE

INST(L) AVE(L) INST(S) AVE(S)

0.5510 0.5511 0.5510 0.5511

GIVE FILTER P2 (HIGH) VALUE

SET FILTER AND TYPE ESC WHEN VALUE IS STABLEINST(L) AVE(L) INST(S) AVE(S)

0.9310 0.9320 0.9110 0.9107

NEW SCALING FACTORS K2 K3 K4

0.9078 1.1070 0.9042

ARE THE SCALES OK ? ( Y / N ) Y

NEW SCALES ARE UPDATED TO EEPROM

FILTER CALIBRATION DONE

FCAL Linearization -1

1) Check that there is no filter in the Transmitter hood.

If there is remove the filter and wait one minute for stabilizing

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If there is remove the filter and wait one minute for stabilizing.

Follow the stabilizing with MES 1 C command

2) Give FCAL-command with your maintenance terminal.

3) MITRAS ask for following inputs:

VISIBILITY

LOW FILTER VALUE

4) Insert the low filter into the Transmitter hood. The label showing the transmittance of filter shall be away from coming light direction.

5) Hit key when the difference between INSTANT and AVE values

has settled. The difference should be less than 0.01.If not restart the FCAL-command.

FCAL Linearization -2

6) MITRAS asks HIGH FILTER VALUE

7) Write down INST and AVE values of low filters

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7) Write down INST and AVE values of low filters.

8) Insert the low filter into the Transmitter hood. The label showing

the transmittance of filter shall look at the receiver LR11.

9) Hit key when the difference between INSTANT and AVE

values has settled. The difference should be less than 0.01. If not restart the FCAL-command.

10) MITRAS shows the new K2, K3, K4 and asks: DO YOU WANT TO STORE THE NEW VALUES INTO EEPROM?

(Y=YES)

11) Write down INST and AVE values of high filter.

12) Write down the new K2, K3, K4 values.

13) Perform CHECK-command and check the results.

14) Update your CALIBRATION SHEET for History File.

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Aligning Optics

Aligning Optics

The long baseline is always aligned first.

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The alignment of the optics starts with aligning the lighttransmitter LP11.

Next go to the LR11.

The horizontal alignment:

The flashing light should be seen at an equal distance ateither side of the receiver unit.

The vertical alignment

The flashing light should be seen (50m baseline and 2,5m

masts) at the height of 0,5m and at the distance of 2m eachsides of the receiver unit.

Aligning Optics

Remove the LPI11.Align the receiver unit in such a way that the flashing light

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g y g gpoints roughly to the center of optics when you look throughthe filters.

Connect the LPI11 back and monitor the R(I) values withterminal.

When the R(I) is within the limits of 1500 to 3500 the

alignment is in order.

Perform a calibration check.

Optics Head Alignment

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1 = Allen screw forvertical adjustment

2 = Allen screws for horizontal adjustment

3 = Set screws for horizontal adjustment4 = Allen screws for

horizontal adjustment

Double baseline optics adjustment

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1 Knob for horizontal adjusting

Direction A

Direction A

1

1

2

2

9606-005

3

3

4

4 4 Knob for vertical locking

3 Knob for vertical adjusting

2 Knob for horizontal locking

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Replacing a Subassembly

Replacement of contamination measurement lamp

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4

5

3

7

C

6

A

9606-006

2

1

B

Replacement of flashlamp

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