Cosworth

Torque sensor systemAPPLICATION NOTE

Research

2 Torque Sensor System Application Note

DisclaimerPi Research makes no representation or warranties of any kind whatsoever with respectto the contents hereof and specifically disclaims any implied warranties of merchantabilityor fitness for any particular purpose. Pi Research shall not be liable for any errorscontained herein or for incidental or consequential damages in connection with thefurnishing, performance or use of the software, associated hardware, or this writtenmaterial.

Pi Research reserves the right to revise this publication from time to time, and to makechanges in the content hereof without obligation to notify any person of such revision orchanges.

A copy of the Pi Research Terms and Conditions of Sale is available on request, andincludes a declaration of the warranty and limitation of liability which apply to allPi Research products and services.

Health and Safety informationUnder the terms of European and UK Health and Safety Legislation, Pi Research isrequired to classify any hazardous materials in the product it supplies and to providerelevant safety information to users.

Any hazardous materials in Pi products are clearly marked with appropriate symbols.Product Safety Data Sheets relating to these materials are available on request.

3Contents

Safety information ................................................................................... 5Transmitter unit battery safety ........................................................ 5Disposal of used batteries .............................................................. 6

About this document ............................................................................... 7

Introduction .............................................................................................. 8

System requirements .............................................................................. 9

Installation .............................................................................................. 10Drive shaft preparation ................................................................. 10Fitting strain gauges ..................................................................... 11Fitting a torque sensor transmitter ............................................... 14Fitting a torque sensor transmitter battery ................................... 15Fitting a torque sensor receiver .................................................... 16

Setup and test ........................................................................................ 17Torque sensor transmitter checks ................................................ 17Torque sensor receiver checks .................................................... 18

Torque sensor monitor software ......................................................... 19Starting the torque sensor monitor software ................................ 20Communications port .................................................................... 21Baud rate ...................................................................................... 21Team code .................................................................................... 22Graph scale .................................................................................. 23Start and stop monitoring of the sensor ....................................... 24Toolbar button .............................................................................. 25


System test and calibration .................................................................. 26System test ................................................................................... 26Possible failures ........................................................................... 28Calibration ..................................................................................... 31Version 6 Setup channel calibration ............................................ 32Zeroing and aging of sensors ....................................................... 35Logging issues .............................................................................. 36

Interpreting torque data ........................................................................ 37Hop/waddle mode ......................................................................... 37Start and steering ......................................................................... 38Gear change ................................................................................. 39Off load zero estimation ............................................................... 40Torque difference/sum ................................................................. 41Frequency response ..................................................................... 42Alternative method to plot frequency response ........................... 43

Specifications ......................................................................................... 44Torque sensor transmitter ............................................................ 44Torque sensor transmitter battery ................................................ 45Strain gauge ................................................................................. 45Torque sensor receiver ................................................................ 45Connectors ................................................................................... 46

Dimensions ............................................................................................. 48Torque sensor transmitter ............................................................ 48Torque sensor receiver ................................................................ 49

Parts numbering .................................................................................... 50Kits ................................................................................................ 50

Contact information ............................................................................... 52

5Safety information

Transmitter unit batterysafety

For full safety information on the batteries read the Product Safety Data Sheet LST 01Lithium /Thionyl Chloride Cells. A copy of this Product Safety Data Sheet is availableon request from Pi Research.

The battery in the transmitter unit contains a number of chemicals and materials, whichcould potentially be hazardous if they leak from the battery.

If a battery exceeds 150C it may leak electrolyte. If a battery is leaking electrolyte takethe actions detailed below.

Accidental Release Measures Do not breath vapours. Do not touch the liquid with bare hands. Use rubber gloves. If the skin has come into contact with the electrolyte it should be washed

thoroughly with water. Graphite powder should be used to absorb the exudation. Seal the leaking battery and graphite powder in plastic bag and dispose of

as Special Waste according to local regulations.

First Aid Measures

InhalationRemove from exposure, rest and keep warm. In severe cases obtain medical attention.

Skin ContactWash off skin thoroughly with water. Remove contaminated clothing and wash beforereuse. In severe cases obtain medical attention.


Eye ContactIrrigate thoroughly with water for at least 15 minutes. Obtain medical attention.

IngestionWash out mouth thoroughly with water and give plenty of water to drink. Obtain medicalattention.

Further TreatmentAll cases of eye contamination, persistent skin irritation and casualties who haveswallowed the electrolyte substance or have been affected by breathing its vapours shouldbe seen by a Doctor.

Disposal of usedbatteries

Do not incinerate used batteries. Such abuse can result in loss of seal, leakage, and/orexplosion of the battery.

Dispose of used batteries in accordance with appropriate local regulations.

7About this document

This document covers the installation and use of the Pi Propshaft torque sensor system.

Some procedures in the document require prior knowledge of Pi PC Software, especiallyin the use of graphs, math channels and naming channels. Refer to your PC SoftwareGuide for more information.

To help you interpret torque data, sample graphs are shown in a section entitledInterpreting torque data.


Introduction

The Pi Torque sensor system uses a Torque sensor transmitter in conjunction with straingauges and a Torque sensor receiver, to measure the torque being applied to a drive shaft.

Strain gauges are fitted to a drive shaft and are connected to a torque sensor transmitterwhich is also fitted on the drive shaft. The torque sensor transmitter converts the outputfrom the strain gauges into a data stream which is then transmitted to a receiver locatedon the car close to the transmitter unit.

The analogue output from the Torque sensor receiver is connected to an analoguechannel of a Pi data logger. The logged data can be then be analysed usingPi PC Software.

The strain gauges should be fitted onto the drive shaft by Pi Research. The Torque sensortransmitter units and Torque sensor receiver units can be fitted by your engineers or byPi Research.

Torque sensor transmitter units can be manufactured to fit drive shafts with diametersbetween 25mm and 30mm. Torque sensor transmitter units can be manufactured to othersizes on request.

To allow Torque sensor transmitters to be used on both drive shafts simultaneously,different transmit frequencies are available.

Always consult Pi Research for recommended gauge installations.

9System requirements

To use the Pi Torque sensor system you need a Pi Research Data Logging System.

Whilst the Propshaft torque sensor system does not require specific system boxcode orPC Software releases, you should consult with Pi Research to ensure that your systemboxcode and PC software are compatible with the Propshaft torque sensor system.


Installation

This section gives information on installing the Torque sensor system.

Drive shaft preparation

It is imperative that the torque sensor transmitter is a precise fit onto the drive shaft.

The loads imposed on the torque sensor transmitter unit are large, and the worst effectoccurs when the drive shaft is under full power at a speed where there is insufficienttraction to stop the wheel from spinning.

Under these circumstances, the drive shaft twists under the imposed loading, and thenwhen the wheel becomes free, the only restraining effect is the inertia of the wheel,bearing and brake assembly. This allows between 100g and 200g of rotational shock tobe experienced by the torque sensor transmitter unit. The effect of this is to try and spinthe drive shaft inside the clamping area of the torque sensor transmitter unit. Following onfrom this, when the recoil of the drive shaft stops, the torque sensor transmitter unit triesto continue rotating around the drive shaft, attempting to free itself from the drive shaft.

The contact area on the drive shaft is much smaller than the bored section of the torquesensor transmitter unit, and most of this is only providing a stabilising effect. The clampingforce is provided on a small ring about 2mm to 3mm wide directly in line with the clampbolts. It is imperative that the surface of the contact area of the torque sensor transmitterunit after boring is smooth and flat, without being polished. This gives the best contactbetween the drive shaft and the torque sensor transmitter unit which enables the rotationalshock loads to accelerate the whole sensor in sympathy with the drive shaft.

If this does not happen, the torque sensor transmitter unit rotates and rips the wires fromthe strain gauge anchor points.

In summary, the drive shaft must be: smooth, with no ripples or no high spots; perfectly cylindrical; unpolished and clean.

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Fitting strain gauges

When fitting strain gauges to drive shafts: choose a position on the drive shaft so that the strain gauges are not in

areas of high temperature or will be subjected to heat soak. It is advisableto stick temperature sensitive labels at 50mm (2") intervals along the driveshafts to obtain their thermal profile before fixing the gauge and torquesensor transmitter unit locations;

use high extension strain gauges. Refer to Pi Research for specifications; surface preparation is vital and the area where the strain gauge will be

fitted on the drive shaft should be etched to provide a good surface for thestrain gauge to adhere to;

use only silicone rubber as the sealing material; do not use teflon tape, use only a tape that bonds to silicone rubber; use 26AWG wire to Raychem 55 specification to connect the strain gauges

to the torque sensor transmitter unit; keep the wires between the strain gauge and the torque sensor transmitter

unit as short as possible and use a fabric type tape to secure them to theshaft;

crimp the wires from the strain gauge to the torque sensor transmitter unitconnector. DO NOT use solder.

Typically the drive shafts will twist considerably, hence the strain gauges will need to bebonded to the drive shafts with a flexible adhesive.

The connecting wires and temperature compensation wires will also need to be mountedsuch that they can move with the twisting of the drive shaft but are not free to vibrate andfracture.


Fitting and connecting strain gaugesThe torque sensor transmitter unit and strain gauges should be fitted to a drive shaftbefore the drive shaft is fitted to a vehicle.1 Clean the drive shaft at the etched areas where the strain gauges are to be

fitted.2 Fit two strain gauges on to each drive shaft so that they will measure torque.The two strain gauges on each drive shaft must be fitted along the long axis of the driveshaft, diagonally opposite each other.3 Seal the strain gauges to the drive shaft using silicone rubber.4 Loosely fit the torque sensor transmitter unit onto the drive shaft at the

position chosen. (Refer to the steps 1 and 2 in the section To fit a transmitterunit below.)

5 Remove the lid from the torque sensor transmitter unit and measure thelengths of wire required to connect the strain gauges to the torque sensortransmitter unit.

The wires should reach to the end of the friction clamp on the torque sensor transmitterunit.6 Cut the wires to length.7 Strip off 2.5mm insulation from each wire, fold the wire back and place it in

the socket contact part with conductors innermost.For the HE14 connector details, refer to the Connectors section of the Specificationssection of this document. Location of the mating connector at the torque sensor transmitterunit is shown in the next figure.8 Using the size 2 position on the crimping tool, crimp the socket contact to form

the metal and then finish with the size 1 position on the crimping tool.9 Crimp the wire clamp part of the contact using the size 2 position on the

crimping tool to form the metal and then finish with the size 1 position on thecrimping tool.

Note: Dont forget to connect the torque sensor transmitter battery lead to the HE14connector.

10 Tape the wires to the shaft so that they will not move when the shaft isrotating.

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11 Mate the HE14 connector to the transmitter unit.This completes the fitting of the strain gauges. To continue the installation, refer to theTo fit a transmitter unit instructions in the next section.

Strain gauge andpower connector

pin 1

pin 5

Location of torque sensor transmitter strain gauge and power connector


Fitting a torque sensortransmitter

When fitting a torque sensor transmitter on a drive shaft: choose a position near to the centre the drive shaft where the torque

sensor transmitter is not in an area of high temperature or will be subjectedto heat soak. Temperatures in excess of 60C (140F) can reduce batterylife. At 80C (176F) the battery life is half that at 50C (122F);

ensure that the torque sensor transmitter is the correct size for the driveshaft diameter;

fit the red coloured transmitter to the left hand drive shaft and the greencoloured transmitter to the right hand drive shaft (left and right hand whenstanding at the rear of the car looking forward);

ensure that the torque sensor transmitter unit will not come into contactwith parts of the car under extreme movement, for example, parts of thesuspension.

To fit a torque sensor transmitter unit:1 Clean the drive shaft and inside mounting faces of the torque sensor

transmitter unit with brake cleaner.2 Place the two halves of the torque sensor transmitter unit around the drive

shaft and fit the bolts so that you can see only one bolt head and one nut at atime. This ensures that they do not upset the balance of the drive shafts.

3 Adjust the position of the torque sensor transmitter unit so that the gaugewires are held in the clamping area of the torque sensor transmitter unit lid.Make allowances for taping required to hold the wires to the drive shaft. Thegauge wires should not be tight or have room to wobble about.

4 Tighten the nuts evenly, and finally torque each nut to 8 Nm (6lbf/ft)(70lbf/in).

5 Fit the lid on the torque sensor transmitter unit.6 Fit the torque sensor transmitter unit battery (see next page).

15

Fitting a torque sensortransmitter battery

The torque sensor transmitter battery is a 3.6V Lithium Thionyl Chloride cell. The only cellcertified for use is the SAFT LS14250.

WARNING: Do not allow batteries go above 150C as they may vent. If ventingdoes occur, handle the batteries using gloves, and wash your hands aftertouching a venting battery. Graphite powder should be used to absorb theexudation. Seal the leaking battery and graphite powder in plastic bag anddispose of as Special Waste according to local regulations. For full handlinginstructions read the Product Safety Data Sheet which is available on requestfrom Pi Research.

When fitting a battery:1 Remove any plastic and paper labelling from the battery to reveal metal

casing.2 Clean the battery metal casing with brake cleaning fluid.3 Insert the battery with the positive connection towards the metal bolt in the

battery compartment.4 Tighten the closing screw with a small coin. Do not use a screwdriver as you

might apply too much force and distort the battery compartment.5 Use a fabric tape to seal the cover against dust and water.6 Fit locking wire through the holes on both sides of the battery case. This will

prevent the battery from being thrown out if the battery compartment coverbecomes loose.


Fitting a torque sensorreceiver

Fitting the torque sensor receiverWhen fitting the torque sensor receiver: choose a position where the torque sensor receiver is not in an area of high

temperature or will be subjected to heat soak. The temperature must notexceed 80C (176F);

the receiver should not be mounted near to a source of electricalinterference e.g. inside any bodywork near the engine. (The rear crashstructure is an ideal site on F1 cars.);

fit the torque sensor receiver with the red coloured base to the left handside of the car and the torque sensor receiver with the green coloured baseto the right hand side of the car, when viewed from the rear of the carlooking forward;

line of sight operation between the correct torque sensor transmitter unitand the torque sensor receiver is required;

the siting should be such that one torque sensor receiver is screened asmuch as possible from the other torque sensor receiver;

looms must be screened and must be run separately as far as is possible; looms must not have any loops at the torque sensor receiver; use anti vibration mounts; do not run other cables or looms, or place objects made from carbon fibre,

close to the plastic cover of the receiver unit.

17

Setup and test

It is important that you take time to check over the Torque sensor system before runningto ensure that you get the best information possible from it.

Torque sensortransmitter checks

1 Remove the lid of the torque sensor transmitter unit and check the gasketseals. Replace any that are worn.

2 Check that the wires from the strain gauges are not nicked or chafed and thatthe wires into the connector are OK.

If a repair is needed then consider extending the wires and moving the transmitter a littlefurther down the shaft. Secure the wires to the shaft with a fabric reinforced tape, not tiewraps. Tie wraps may damage to the wires.3 Check that the connectors have not had any dust ingress.4 Use a contact cleaner such as Servisol contact cleaner to blow any dust from

the internals.5 Carefully check the wires to the strain gauge and make sure that they are not

crossing each other in the area of the rubber gasket seal. Refit the lid.6 Remove the battery from the battery compartment and clean the battery with

brake cleaner.7 Check the transmitter battery terminal connection has not become loose.If it is a new battery, remove the labels and clean the battery with brake cleaner.8 Fit the battery into the battery compartment and fit the cover. Use a fabric tape

to seal the cover against dust and water.9 Check that the battery voltage is greater than 3.2V when powering the sensor.

Fit a new battery if the voltage is below 3.2V.10 Fit locking wire through the holes on both sides of the battery compartment.

This will prevent the battery from being thrown out if the battery compartmentcover becomes loose.


Torque sensor receiverchecks

1 Clean the torque sensor receiver unit using Servisol contact cleaner.2 Ensure that the torque sensor receiver unit is securely fixed to the vehicle.3 Check that the loom is secure and does not interfere with any other fittings on

the vehicle.4 Apply power to the torque sensor receiver unit. The illumination of the LEDs

indicates the following:

LED colour Indicates

Red Torque value is stable.Yellow Data is being received. The LED is dimmed or flashing when noise is

received.Green Data with the correct codes has been decoded and output. Cancels

after 10ms if no valid data packet has been received.

RedLED

YellowLED

GreenLED

Torque sensor receiver LED indicators

Note: The torque sensor transmitter sleeps to conserve power. This shows as a pulsingof the yellow and green LEDs on the torque sensor receiver. The Europeanspecification unit sleeps for approximately 1.5 seconds, the USA specification for 10seconds (FCC regulations). If the transmitter notices that significant activity isoccurring, then data will be transmitted and the red LED will extinguish to signify this.

19

Torque sensor monitor software

The Torque sensor monitor software is a stand alone program which you use to check thereadings being sent by a torque sensor transmitter to a torque sensor receiver. Thisenables offset and calibration values to be obtained away from the full logger system.

The Torque sensor monitor software is a 32-bit program and will function correctly usingWindows 98. Windows NT is not supported.

The Torque sensor monitor software operates using the debug loom provided. The debugloom connects a torque sensor receiver to a COM port on a PC. The debug loom also hasterminals to connect to a 12V power supply, and terminal sockets which provide a groundand an analogue output signal for measurement using a meter.

The Torque sensor monitor software, a help file and a team code file are supplied on afloppy disk.

To install the torque sensor monitor software on your computer:1 Create a suitably named folder on your hard disk.2 Insert the floppy disk containing the torque monitor software into the floppy

disk drive. Copy the entire contents of the floppy disk into the new folder.3 Create a shortcut on the desktop to the file tork32.exe in the folder you

created in step 1 above.A Pi Torque icon is created on the desktop.

Refer to the documentation that came with your computer for details on how to create ashortcut.


Starting the torquesensor monitorsoftware

To start the torque monitor software:1 Locate and double click on the Pi Torque icon on the desktop. The Torque

Sensor Monitor window appears.

Torque Sensor Monitor window

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Communications port

You can choose either COM1 or COM2 as the communications port. This option may onlybe changed when the program is not monitoring a torque sensor.

To select a communications port:1 Choose "Port" from the main menu. A drop down menu appears.The current selection is shown dimmed and checked. The alternative port is shown innormal text.2 You can accept the current setting by selecting "Port" again, or you can click

on the alternative value to choose it.The selection must correspond to the port on your computer to which the torque sensorreceiver debug loom is connected. The default value is COM1.

Baud rate

You can choose 9600 baud or 19200 baud for the data rate for the selected COM port.This option may only be changed when the program is not monitoring a torque sensor.

To select a baud rate:1 Choose "Baud Rate" from the main menu. A drop down menu appears.The current selection is shown dimmed and checked. The alternative value to which thebaud rate may be set is shown in normal text.2 You can accept the current setting by choosing "Baud Rate" again, or you can

click on the alternative value to choose it.The selection must correspond to the baud rate set on the torque sensor system. Thedefault value is 9600.

You will be advised if your torque sensor system runs at the 19200 baud rate.


Team code

You can choose the team code number for the torque sensor in use. You will be advisedof the team codes for your sensors when they are despatched to you. This option may onlybe changed when the program is not monitoring a torque sensor.

To select a Team code:1 Choose Team from the main menu. The Select code button appears.2 Click on the button. The Select Team Code dialog appears.3 Choose the appropriate code from the list.If the code chosen from the list does not match the code for the torque sensor systemconnected to the PC no data will be displayed during monitoring and monitoring will stopautomatically after a short period.

If you purchase additional torque sensors you can join the new team code file and thecurrent team code files together.

To join team code files1 Insert the floppy disk containing the new team code definition file into the

floppy disk drive of your computer.2 Start an MS-DOS session.Refer to the documentation that came with your computer for information on starting aDOS session.3 Make sure that you are in the Torque sensor folder.4 Type copy /B torque.def torque.def+A:torque.def and press

the (Enter) key.The details from the torque.def file on the floppy disk will be appended to thetorque.def file on the hard disk.

23

Graph scale

The graph scale determines the span of the graphical display from fine (a range of +50 to50) to coarse (a range of +5000 to 5000). The scale may be changed while monitoringis in progress, in which case the graph will be cleared and the graph will start again fromthe left hand side.

To change the graph scale:1 Choose Scale from the main menu. A drop down menu appears.The current selection is shown dimmed and checked. The alternative value is shown innormal text.2 You can accept the current value by choosing Scale again, or you can click

on the alternative value to choose it.If the graph scale is set to fine and the graph has been filled completely, the monitorprogram will automatically recalculate the graph axes to offset the graphical display aboutthe last reading. For example if the last measured value was 5, the new graph range willbe from +55 to 45.


Start and stopmonitoring of thesensor

The torque sensor receiver unit contains a receiver module and a signal processingmodule.

The torque sensor monitor software works by accepting 50 readings at a time from thereceiver module. This is the raw data before it is processed by the decode and analoguecircuitry in the signal processing module prior to being sent to the logger.

The torque sensor monitor software displays certain values in a window on the PC. Thesevalues are shown in the next table.

Torque monitor window Remarks

Current The last value of the 50 readings.Maximum The maximum value of the 50 readings.Minimum The minimum value of the 50 readings.Filtered This is the value that the signal processing module would

use to generate an analogue output signal.Average The mean value of the 50 readings. This value is used

to plot a point on a graph.

The range of the torque raw value is 4096 to +4095 counts. At zero torque the valueshould be inside the range +50 to 50 counts.

Note: The transmission range of the torque sensor system is short (10m) and requiresline of sight between the torque sensor transmitter unit and the torque sensor receiverunit. Torque sensor receivers will therefore not decode correctly data from torquesensor transmitters which are screened by walls or other obstructions, or from carswhich are out on the track.

25

Toolbar button

The button on the toolbar indicates the monitoring status. When the button is green thesystem is not monitoring, and when it is red the system is monitoring. If no sensor isdetected from starting monitoring of the sensor, monitoring will automatically stop. If asensor is connected after monitoring has started, the sensor will not be detected. Stop andrestart the monitoring to ensure the sensor is detected.

To start monitoring:1 Choose Start from the Monitor menu, or press the green button on the

toolbar.

Torque Sensor Monitor window when monitoring is in progress

To stop monitoring:1 Choose Stop from the Monitor menu, or press the red button on the toolbar.


System test and calibration

This section gives details on testing and calibrating the torque sensor system afterinstallation. Although parts of this section refer to Pi Version 6 PC software, if you are usingdifferent Pi PC software for setting up channels and analysing data, you should refer tothe relevant manuals for information.

To perform a system test you need the following items: a torque sensor receiver debug loom; a PC with the torque sensor monitor software installed; a 12V power supply.

System test

To perform a system test:1 Disconnect the torque sensor receiver being tested from the logging loom.

Connect the torque sensor receiver debug loom to the torque sensor receiver.2 Connect the torque sensor receiver debug loom to the selected COM port on

the PC.3 Connect the torque sensor receiver debug loom to the 12V power supply. The

red plug is for +ve and black plug is for ve.4 On the PC run the torque sensor monitor software and start monitoring.

Check the current value on the PC display.This should be within 50 counts from zero.5 Twist the drive shaft. Hold the drive shaft in this position until the torque

sensor receiver acquires new data from the torque sensor transmitter(2 seconds for European specification systems and 10 seconds for USAspecification systems).

27

You can use your hands to twist the drive shaft or you can turn the wheel on the end ofthe drive shaft. The engine end of the drive shaft must be turned in its normal direction.The wheel end of the drive shaft must be turned backwards.

The current value on the PC display should change by a few counts.6 Twist the drive shaft in the opposite direction.The value on the PC display should change by a similar amount in the opposite direction.The sign of the calibration value used depends on the sense that the strain gauges havebeen wired and the side that the drive shaft is being used on. It is normal for one side tohave a positive sign and the other side to have a negative sign.7 Disconnect the torque sensor receiver debug loom from the torque sensor

receiver. Connect torque sensor receiver to the logging loom.8 Repeat the above test, using Watch Channels in raw mode in Version 6 Setup.For information on watching channels refer to your PC Software Guide.

It is normal to get more sensitive results from the torque sensor monitor software as thevalues from the torque sensor system are transmitted as a 13-bit number and have notbeen measured at 12-bit resolution in a logger.


Possible failures

Intermittent RF FailureIntermittent RF failure usually exhibits a stepped response, with flat lining at a non zerovalue being the extreme case. This flat lining can also be caused by a flat battery in thetorque sensor transmitter, although it will normally be preceded by a gradual shift in thezero point and ultimately flat lining near the zero point. It will also exhibit flat lining if thebattery restraint is inadequate and the battery is thrown from the battery compartment.

The graph below shows the effects of RF failure. The output signal from the torque sensorreceiver freezes at some value for a period of time, from a very short interval (andtherefore difficult to spot) to a much longer interval. The reason for this is that the receivergets no updated messages, so holds the last value received.

The main difference between RF failure and gauge failure is that the error values are notrepeated (as in gauge failure) but are essentially random, and are usually in the rangenormally seen by the sensor.

transmitting correctly

transmitter failed

Example of RF failure

29

Gauge failureGauge failure also exhibits flat lining but usually at a maximum, minimum or zero reading.This may not be exactly zero as it will be offset by the original error in the gauge zero point,but this is normally small (50 counts).The graph below shows the output of a system when a wire fatigue failure occurred on thestrain gauge. The output is sometimes present but keeps returning to zero counts (raw)which is its most negative value.

Gauge failure


Power upOn power up, the torque sensor transmitter unit sends a series of synthesized sine signals.The sine signal frequencies are at 16.96Hz, 1.06Hz, 2.12Hz, 4.28Hz, 8.48Hz and finally16.96Hz again. The reception of these sine signals during normal use indicates that thesensor has detected some disturbance in its power. This could be either from a loosebattery connection, or intermittent contact in the connection plug, or intermittent shortingdue to chafed wiring.

31

Calibration

Care should be used when calibrating the drive shafts. Two similar drive shafts can matcheach other quite closely, with typically less than 5% difference between them. To getquantitative readings, calibration should be performed over as wide an operating range aspossible, without damaging the drive shafts.

The output from the torque sensor system is very linear, so multi-point calibration is notrequired. (Track noise exceeds any error introduced by non-linearity).The calibration range should cover, if possible, just on load e.g. 5%, to full load in top gear.Remember to share the expected torque values between the two drive shafts. This shouldencompass about 10% to 20% of the total range of the sensor (half of the range beingnegative).The value entered into the logging is a measurement of the torque required to generatea 1 count change at 12-bit resolution or 10-bit resolution in the logged reading. Thisresolution is governed by the logger.

If the torque sensor monitor software is used to calibrate the shaft, then the resolution ofthe logger must be taken into account by multiplying the value of torque per count fromthe torque sensor receiver output at 13-bit resolution, by two for a 12-bit resolution loggingsystem, and by eight for a 10-bit resolution logging system. Beware of rounding errors.Always calculate directly from the original numbers.

Examples of recorded data and calibrations for different system resolutions are given inthe following section, Version 6 Setup channel calibration in this document.


Version 6 Setup channelcalibration

You will need to calibrate a channel using Version 6 Setup. Details on calibrating a channelare given in the Setup section of Version 6 PC Software Guide. You use an ax+b calibrationtype for the channel.

Example data and calibration information for different logger resolutions are given below.

Example recorded data

Nominal Actual load Readings in Torque Monitor software

5% load 44Nm +68100% load 880Nm +1360

13 bits = (880 44)1360 68 =8361292

= 0.64706 Nm per count

Calibration for 13-bit resolution

12 bits = =

1.29412 Nm per count

(880 44) x 21360 68

16721292

=


10 bits = =

5.17647 Nm per count=

66881292

(880 44) x 81360 68


To ensure best accuracy in the final measured values do not round numbers atintermediate stages of the calculation e.g. do not round 0.64706Nm per count to

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0.65 Nm per count because this would give a 10-bit value of 5.2Nm per count and an errorof +0.45%.

No-load (0%) readings from the torque sensor monitor software may not be exactly zero.This is due to small imbalances of the strain gauge resistor bridge caused by movementof the metal of the drive shaft and any residual errors of the sensor or bridge attachment.This error should be within 25 counts.

You will need to set the maximum and minimum calibrated channel values in Version 6Setup. Refer to the Changing channel parameters section of the Version 6 PC SoftwareGuide for full details on changing the channel parameters.

To set the maximum and minimum values:1 Choose Change Channel Parameters ... from the Calibrate menu. The

Channel Parameter Editor dialog appears.2 In the Units box enter Nm.3 Set the Precision value to 3.4 Set the Max value to 6000, and the Min. value to 6000.5 Choose OK.You must now enter the calibration values. You will need to enter a value for a Y co-ordinateand an X co-ordinate for two points.


To enter calibration values:1 Select the Ins button. The Co-ordinate entry dialog appears.2 Enter the Y value and then the X value for the two points.3 From the Calibrate menu choose Calibration Type, and then check the ax+b

option.Enter the values you have calculated from your recorded data. The values in the tablebelow are examples only and your own data will give different values.

Points for ax+b calibration in Version 6 Setup

Co-ordinate entry 12-bit 10-bit Value

Y co-ordinate 1 0 0 NmX co-ordinate 1 2048 512 counts

Y co-ordinate 2 1294.12 517.647 NmX co-ordinate 2 3048 612 counts

Note: In the above table the Y co-ordinate 2 value is scaled to allow a sensible numberof counts difference to be used between the X co-ordinate 1 and 2 values.

35

Zeroing and aging ofsensors

Zeroing of the sensors on the car should be done at the beginning of the day, and if it is anew drive shaft, at other reasonable intervals for about the first 20 laps. After this periodthe drive shafts and strain gauges settle down to a consistent zero point. If it is noted thatthis zero is beginning to move again, be prepared to change the shaft as it is almostcertain that the strain gauges will fail totally soon. (The only other reason for the zero tomove is that the torque sensor transmitter battery is going flat.)A zero can be checked for a moving car by plotting left torque against right torque andviewing the data for 100Nm for each axis. What will probably appear is a crossing pointfor the drive shafts when an upshift gear change occurs, but only when the car is goingstraight. This is illustrated in the Offload zero graph in the Interpreting torque data sectionof this application note.

Recalibration of a new shaft after the first test day should be considered as the settlingdown period may have slightly changed the calibration.

Shafts which operate in excess of their elastic limit will continue to show progressive creepof the zero position.


Logging issues

To log the torque sensor system data you will need to create two analogue channels inVersion 6 Setup. If you give similar names to the channels e.g. Torque_RR and Torque_RLthe two channel names will appear in channel list close together. This will help whencreating math channels or graphs.

The frequency response of the sensor is designed to give an upper 3dB limit at 25Hz. Thelogging rate should therefore be chosen appropriately and 100Hz or more isrecommended. Logging at too slow a rate will result in an aliased display at each gearchange.

Some reasons why the data is not as expected can be: Variability due to fluctuations in the track. Check the wheel contact forces,

and push rod strains. Check for contact with kerbs. Effect of the springiness of the drive shaft. Look at RPM and wheelspeed.

The differences appear much more exaggerated in the drive shaft. Violence of gear changes. This can be up to 8 times the normal loading and

violent gear changes are frequently the cause of strain gauge failure. How straight is the straight? Check with steering angle, crosswind effects

etc. Relaxation of the built up torque in a shaft when the wheel unsticks. Check

the wheel contact forces, look at wheelspeed.

37

Interpreting torque data

This section contains graphs of data, and explains how to interpret the graphs. This shouldhelp you when examining graphs of your own data.

Hop/waddle mode

This graph is a distance graph, with right torque and left torque channels plotted againstdistance.

The traces at 3405 seconds show the oscillations set up in the shafts running in phase,(hop mode) where the energy is built up in the shafts and then transferred to the car. At3411 seconds the suspension changes to a situation where the energy is built up in oneshaft in preference to the other. This energy is then transferred to the car while the energyis built up in the other shaft, (waddle mode).At 3440 seconds the waddle mode starts again but changes abruptly at 3443 secondswhen it returns to hop mode.

Hop/waddle mode


Start and steering

This graph shows pulling out of the garage and turning a corner. The graph is a time graphwhich has three channels; Steering Angle, right torque, and left torque. The graph showsa spike at 4344 seconds, which is probably a gear selection. Then left and right tracesfollow each other as the torque is applied. There is probably no wheelspin here. Steeringis turned at 46 seconds which generates differing torques and the torque traces diverge.

At 47.5 seconds the torque input exceeds that of the tyres and the traces start to convergeviolently, probably as a result of wheelspin. Wheelspin is probably evident until about 50seconds where the steering is beginning to straighten. At approximately 52 seconds thethrottle is closed and the torque in the shafts falls away rapidly and in phase with eachother. As the steering is returned to straight the traces gently track each other.

The sections of this graph which give confidence in the correctness of the data are thecorrelation between the left and right traces up to 46 seconds and the section where thetraces fall rapidly at 52.1 seconds.

The correlation between the two traces when the car is running straight, with little powerinput, should be close.

Start and steering graph

39

Gear change

This is a time graph which has three channels; torque, right wheelspeed and RPM.

The graph shows a gear change at approximately 134.50 seconds. When the power isapplied the wheel slips slightly at 134.66 seconds and produces little torque in the shaft.When the grip returns, it slows the wheel and the engine RPM is reduced quite rapidly asthe rotational energy is transferred into the shaft generating a large increase in the torque.

The energy in the shaft then causes the car to increase in speed and the torque reduces,the load on the engine falls away and the RPM increases. This produces an oscillatingsystem between the engine, shaft and tyre, which dies away over the next 0.5 seconds.

torque

rpm

wheelspeed

Time graph showing the effect of a gear change on torque


Off load zero estimation

This XY plot, using dots, of left torque against right torque for a section of the data wherethere are gear changes along a fixed straight (in fixed zoom area mode). The scales havebeen set to show just the section where there is little torque (100Nm on both axes).It shows a concentration of dots in the centre which are centred on zero horizontally butat about 6 vertically. This could be caused by drag in the bearings or brakes. It would beprudent to check the shaft zeros when the car is at rest in the garage.

This type of graph can be used to check the zeros around the track, and can be used toidentify where a problem has occurred. This allows you to use the data up to the pointwhere the fault appears.

Off load zero estimation

41

Torque difference/sum

Two math channels, torque difference and torque sum were created in Version 6 AnalysisPC Software. The graph below is an XY plot, using dots, of these two math channels.Torque difference is the vertical axis and torque sum is the horizontal axis. The graphshows the action of the differential and a concentration of dots at the full power straightahead condition.

These types of graph are not always aligned with the zero difference line, as some circuitsare not of the "straights with corners" type, but have a more circular plan. This causes abias to one side as significant amounts of time are taken cornering with power applied.

When the sum is less than zero the car is slowing and a differential action can clearly beseen. At the smaller area of 0 to 1.5 the differential action is less clear but still exists.

full power straight

off power/braking on power/accelerating

Plot of torque difference against torque sum


Frequency response

With torque sensor data from a full lap plotted against frequency, a graph of the frequencyresponse of the engine, drive shaft and wheel is generated.

The graph below shows the right torque sensor signal frequency response.

You could equally graph the left torque signal or gain a comparison by plotting both leftand right signals on the same graph.

DC content

natural roll-off ofchassis/tyre effects

peak possibly dueto chassis effects

Frequency response of the right torque signal

43

Alternative method toplot frequency response

There is another way to generate a plot which removes the problem of the DC componentsin the data. This method utilises the math function Deriv3 in Version 6 Analysis software.

In Version 6 Analysis create a math channel of the form:

UserFn ( choose , Throttle > 90 , Deriv3 ( Torque_RR + Torque_RL ) , 0 )

This will produce a graph which gives a plot of the frequencies of the drive train, wheelsetc.

The graph below is a frequency plot and shows two laps plotted against a math channelof the form above (which is named torque_freq). The smoothing is set to 63 points andlinear scales are used.

lap 1 lap 2

Alternative frequency plot

Care should be taken in its interpretation as there seems to be some variability in thegraph produced from laps even on the same outing. This is probably due to differences inthe driving. The inclusion of the throttle term in the math channel helps to clarify the resultdisplayed on the graph.


Specifications

Torque sensortransmitter

Torque sensor transmitter specifications

Description Value

Shaft size 2530mm1Max RPM 2200Centrifugal loading 0.5g per Km/hBattery life at 20C 100% on 32h, 10% on 147hBattery life at 50C 100% on 15h, 10% on 79hBattery life at 80C 100% on 7.5h, 10% on 53hMeasurements 240 readings/secResolution 13 bitsGain of strain gauge amplifier 35.42Transmit frequency 400450MHz2Operating temperature +10C to +80C (+40F to +176F)Weight 150g including batteryEnvironmental IP642

1 Outside this range contact Pi Research.

2 Transmit frequency depends upon use.

45

Torque sensortransmitter battery

The torque sensor transmitter battery is a 3.6V Lithium Thionyl Chloride cell. The only cellcertified for use is the SAFT LS14250.

Strain gauge

Please contact Pi Research for strain gauge specifications.

Torque sensor receiver

Torque sensor receiver specifications

Description Value

Resolution 12 bitsFrequency response 0 25HzGain of receiver 1 or 2Operating voltage 10V 16V DCOutput 2.505VOffset 2.505VOperating current 50mAOperating temperature +10C to +80C (+40F to +176F)Weight 75gEnvironmental IP65


Connectors

Strain gauge connection details

Connection Wire colour Connection Wire colour

Excitation +ve Red Excitation ve BlueSignal +ve Green (or White) Signal ve Yellow (or Black)

Torque sensor transmitter connector details

Connector Mating connector

AMP HE14 (5 pin plug) AMP HE14 (5 pin socket)

Torque sensor transmitter connector pin details

Pin Function Pin Function

1 Battery +ve 4 Signal ve2 Excitation +ve 5 Excitation ve (Ground)3 Signal +ve

47

Torque sensor receiver connector details

Connector Mating connector

AS0-06-05SN-HE AS6-06-05PN-HE

AS0-06-05SN-HE

Torque sensor receiver connector pin details

Pin Function Pin Function

1 +12V 4 no connection2 Ground 5 no connection3 05V output (no shaft load = 2.5V)


Dimensions

Torque sensortransmitter

64.02.52"

64.o

2.52

"

43.81.72"

62.0 typical2.44" typical

8.0 typical0.32" typical

38.01.50" Note:The diameter when rotating

is 66.0 mm (2.60").

Dimensions in millimetres and inches

49

Torque sensor receiver

26.5

(1.04

")

48.0 (1.89")

86.5

(3.40

")92

.5 (3

.64")

6.0

(0.25

)

12.5

(0.5")

2.5

(0.10

)"

M43 posns

144.

0 (5.

66")

18.0(0.71)

18.0(0.71)

Dimensions in millimetres and inches


Parts numbering

Kits

Torque sensor kit Europe

Kit Part Number Quantity

Torque sensor kit Europe 30B-050331 ComprisingTorque sensor Tx RHS Europe 01B-050322 1Torque sensor Tx LHS Europe 01B-050323 1Torque sensor Rx RHS Europe 01B-050324 1Torque sensor Rx LHS Europe 01B-050325 1Installation kit 13B-050294 1

Torque sensor kit USA


Torque sensor kit USA 30B-050332 ComprisingTorque sensor Tx RHS USA 01B-050326 1Torque sensor Tx LHS USA 01B-050327 1Torque sensor Rx RHS USA 01B-050328 1Torque sensor Rx LHS USA 01B-050329 1Installation kit 13B-050294 1

51

Installation kit


Installation kit 13B-050294 ComprisingSwitch cleaner super Servisol 32A-0048 1Tx battery 06B-0012 4Rx debug/monitor loom 03E-1634 1Tx gaskets 10B-050338-1 4Crimp tool 28A-0002 1Torque sensor system Application Note 29B-071175 1Right side Rx sensor loom 03E-15691 1Left side Rx sensor loom 03E-15691 1Twin shaft strain gauge kit 13B-050332 1

1 State length of loom when ordering

Twin shaft strain gauge kit


Twin shaft strain gauge kit 13B-050332 ComprisingGauging instructions 29B-071176-1E 1Gauges 21A-0078 4Tx battery loom 03E-1635 2Tx connector 09G-0209 2Crimp terminal 09F-0044 20


Contact information

For more information about Pi products and details of worldwide authorised agents,please contact:

Pi ResearchBrookfield Motorsports CentreTwentypence RoadCottenhamCAMBRIDGEUK Customer Support Tel +44 (0) 1954 253600CB4 8PS Fax +44 (0) 1954 253601

Pi Research, Inc.8250 HaverstickSuite #275IndianapolisIN 46240 Tel +1 (317) 259-8900USA Fax +1 (317) 259-0137

Research

Part Number: 29B-071175-6E

November 2003

Pi Research, 1998, 2001, 2003

Pi and the Pi logo are trademarks of Pi Group Limited

www.piresearch.com

Safety information Transmitter unit battery safety Disposal of used batteries About this document Introduction System requirements Installation Drive shaft preparation Fitting strain gauges Fitting a torque sensor transmitter Fitting a torque sensor transmitter battery Fitting a torque sensor receiver Setup and test Torque sensor transmitter checks Torque sensor receiver checks Torque sensor monitor software Starting the torque sensor monitor software Communications port Baud rate Team code Graph scale Start and stop monitoring of the sensor Toolbar button System test and calibration System test Possible failures Calibration Version 6 Setup channel calibration Zeroing and aging of sensors Logging issues Interpreting torque data Hop/waddle mode Start and steering Gear change Off load zero estimation Torque difference/sum Frequency response Alternative method to plot frequency response Specifications Torque sensor transmitter Torque sensor transmitter battery Strain gauge Torque sensor receiver Connectors Dimensions Torque sensor transmitter Torque sensor receiver Parts numbering Kits Contact information

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