VEMS v3.2 EGT instructions

Step One - Install components

The key component is the AD597 IC which is shown soldered into place here:

We need to provide power to the chip, C37 works as a power supply filter, you'll need to check that it is installed
first. Its value is 220nF and comes in a strip of 8 in the Rescue Kit 2. You can see its placement at the top
right-hand corner of the AD597 chip, in the picture above.

L4 is used to smooth any noise from the thermocouple, in most cases this is not needed, so either a thin
wire or a 10ohm resistor can be used, L4 is on the bottom of the board and can be identified in this picture:

The resistor at the top right with the value '100'

And the last job is to short out the pads for C44 which is done by connecting a wire across the pads below pins
3 & 4 of AD597, shown here: (Not required for v3.3 and newer boards)

Step Two - Test power supply

Now we need to test the power supply to AD597. Put your DVM across pins 4&7 and read the voltage, it should be
around that of the supply voltage.
Disconnect the power supply.
Next we need to ensure that pins 5&6 are connected, use your DV to check that resistance is 0Ohms
With some EGT sensors the sensor body is not connected to ground, with the DVM still set for measuring resistance
test the resistance of the sensor's body against each of the two pins, if you find that one has zero resistance
you can skip the next step.

Step Three - Bridge common ground

If your EGT sensor body is not connected to the sensor ground you will need to bridge SG9, this is done by soldering
a link across the open pads directly below AD597's pin one.

Check that pins 1,3 & 4 are all connected (zero resistance) with your DVM.

Step Four - Connecting EGT sensor

To connect the EGT sensor you will have to solder the correct wire (K type) directly to the board, to enable the
sensor to be disconnected a temperature compensated plug will be needed, you can either use a case mounted
connector or a plug and socket (see the Example EGT Sensor section at the bottom of this page).
Connect the EGT+ wire (Green) to Pin 1 and EGT- (White) to Pin 8 of the AD597:

Connect power to the board and test the voltage between pins 1 & 8, at 25degrees C the voltage will be approximately
1mV, which is a little below what many DVMs will read, so to check that the sensor is working put it on the shaft of
your soldering iron, you should see the voltage begin to rise.
Finally check the amplified signal, by measuring the voltage between pins 4&6. At room temperature the voltage will
read around 0.29V. Once again you can use the heat of your soldering iron to see the voltage rise as the thermocouple
heats up

Step Five - Sensor calibration

Before we can rely on the sensor's readings we need to calibrate VEMS. This is best done using boiling water as we know
that at sea-level this boils at 100degreesC. Make sure that the sensor does not touch the sides of the vessel containing
the boiling water as this will result in an inaccurate reading. At 100degreesC the voltage fromt the sensor (measured
across pins 1&8) should read:4.095mV and AD597's output (pins 4&6) will be 1005mV.

Calibration is required to enable VEMS to display and log the temperature value correctly, there are two values in the
Config file that are used to do this:
egt1_cal=40 # EGT calibration multiplier
egt1_offs=00 # EGT offset (signed e.g. 0xF0 is -1)
(The change values are quite small so try increasing in steps of +/-0x5 initially.)
The EGT reading should be on the LCD screen's first page, to show EGT alone you can use Bray terminal to change to
page 8 by using the command: Manmlp08
Put the first few centimeters of the thermocouple onto some ice and watch the value on the scree drop.
Adjust the calibration values until the egt reading is zero. Then using a known temperature heat source (like boiling water) to
Check that the egt value is correct across a wide range.

Example EGT Sensor

The sensor that was used by the author was made up from the following parts:

1 x XF-329-FAR: Thermocouple MI 1.5x150mm (Farnell order code: 424-8193)
1 x FC-001 Thermocouple compression gland nut (Farnell order code: 708-1349)
1 x 0220 0002: Mini K type socket (Farnell order code: 469-1349)
1 x 0220 0001: Mini K type plug (Farnell order code: 469-1325)
2 x Mini thermocouple cable clamps (Farnell order code: 67408411)
You will also require K type thermocouple cable (Farnell order code: 708-5904)
Although this seems to only be available in 25m lengths

Original information came from:
http://www.vems-group.org/wiki/index.php?page=GenBoard%2FManual%2FExhaustGasTemp