MoTeC Global Forum

Hi all,

On the M800, I'm wanting to use the stock engine temperature sensor as it has 3 pins and serves the in-dash temp gauge.

So I have developed a calibration curve (resistance vs temp C) for the sensor.

However in the custom sensor setup, for the AT, the fields are volts and Temp. I can use V=IR to establish V but I need to know the current ..... or am I going about setting up the calibration table incorrectly?

Also can we use another AT for the Air temp apart from AT1 ?

Thanks for the help

Bazz

Hi Bazz,
To work out your voltage from resistance you need to take in to account the pull up resistor (1000 ohms on M800) supply voltage (5V) and the sensor resistance at a particular temperature. The calculation is:
V=Supply V x (R/(Pull-up+R)).
I have attached a spread sheet which I use for this to make it easier, just fill in the pink cells and you will have your calibration in volts.

Cheers Ross,

We are back on the dyno again on Wednesday and this is one less thing that Lee has to worry about

It was the pull up value I was needing, so it's all good now, thanks

Hopefully the timing belt will stay on this time

Ross's answer surpassed mine over on EFI101 with that spreadsheet, that will come in handy for sure!

Forgot to say, you can use any AT Input for Air Temp. We normally use AT1 and AT2 for Air Temp and Engine Temp and if you were to upgrade a file from an M4 or M48 this is where they would be asigned. I would say that it is probably a good idea to stick to this convention but it is up to you.

Thanks John and Ross, you both had the answer

John, I had actually used your hint successfully, but as you say the spreadsheet is a handy item to have available for future use.

Cheers Guys