Suggested method of EGT input calibration / verification.

Quick hint: if EGT reading goes down (often rails to 0) when sensor temp goes up, swap the EGT sensor polarity.

Needed for calibration:

For offset-calibration, only an alligator clip is needed.

Round device typical EGT calibration value: 157 (0x9d).

If calibrating, start from this.

Calibration is for device input, NOT the sensor. No need to calibrate if using with a different sensor.

Recently (since 2008-03) EGT input is calibrated.

(the default value gives smaller reproducible error than the error related to sensor placement).

Calibration is useful verification any time one .

Offset calibration

Before adjusting offset, make sure egt calibration has a reasonable (near 157 value, say +- 8). If it's way off, like 0 or 255, you will have to repeat offset step later, so better start with a reasonable offset.

offset: 0-255 (device dependent, no typical value)

Now follow to EGT calibration step:

EGT calibration with 15-45mV signal

A voltage divider (or hot EGT sensor) can be used to provide a small appr 30 mV signal. Maybe divide from a 4V signal (eg. temporarily steal from wbo2 pump- ),

result: 4V * 1k / (100k + 1k) = 39.6mV

example calculation:

This 39.6mV is equivalent to 39.6 * 25C + 27C = 990C + 27C = 1017C

(where +27C is the cold junction temperature).

Adjust EGT calibration until reading is 1017C.

That's all. Attach the alligator-clip again (0mV) and verify that cold-junction temperature is still OK. (if offset was adjusted with a weird calibration value, it might be off now: than go back to offset adjustment).

Take note of the offset and calibration values for future reference (with permanent pen on the side or on a white tape on a cable).

Ice / Boiling water - because of the 100C (=4mV) not as precise as the 15-45mV signal above

Set the offset to 255 and the calibration to 157.

Adjust the calibration until you get a 100degree difference between the ice and boiling water - then use the offset to set the temperature so that it reads 0 in ice, and check the boiling water temperature to ensure that the temps are scaling properly.