MoTeC Global Forum

Hi there,

I've been running my car using various sensors hooked up to gauges for a while.

I've been using a STACK solid state pressure sensor (0-10 Bar), 0-5V to measure oil and fuel pressure and a SPADesign 0-5V temperature sensor hooked up to SPADesign digital gauges to measure water and oil temperature.

The STACK pressure sensor is a ST747 with a 1/8" NPT thread:



And the SPADesign sensor is a TSU-110-FL with a 1/8" NPT thread:



I now want to route all of these into my new MoTeC M800 ECU to allow me to datalog their outputs and possibly relay them to a mini-dash display. Some sensor values are also used to trigger oil pumps and cooling fans.

Does anyone have experience with using these sensors on MoTeCs?

I'm going to do a manual calibration check of the output of the temperature sensors so that I can accurately know signal voltage with respect to temperature, but is it possible to do custom calibrations for 0-5V three-wire temperature sensors? (I've only seen them for variable resistance 2-wire sensors). If so, do I just need to tabulate the signal voltage next to temperature in the Motec software?

I'd rather stick with these sensors if possible since I've not a lot of room to modify some of the locations they are situated in to a more common M12 thread.

Cheers,

George.

Most pressure sensors are linear...
sometimes 0v = 0 pressure 5v = full pressure , or in most cases 0.5v = 0 pressure 4,5v = full pressure and there are cases that they will be 0.2v to 4.8v

I would suggest you connect it to your M800 next to a known pressure reading. 0 pressure`s voltage is easy to know, now just plot a voltage point for a known pressure that you exert on the unknown senor. If its 5bar, then just extrapolate the calibration line from 0 pressure reading to the known reading and beyond.


temperature sensors are way more difficult to do. When you do them, make sure you give the unknown and the known sensor enough time to stabilize at a reading. If you have both in a kettle and just ramp the temp up the cal will most likely be bad since different sensors dont respond at the same rate. You really need a constant temperature source with the whole sensing part of the sensor exposed to the medium you are using to calibrate it. Best Idea would be to get the calibration curve from the manufacturer.

Martin,
Been looking for a 1/8 NPT threaded water temp sensor compatible with M series ecu for a while, any ideas ?

Yes, send me a mail

Thermistors will have a known value at 25c, this will be the cal curve, "1K" "5K" "10K" etc. They are all very similar if not exact.

http://www.motec.com/forum/viewtopic.php?f=11&t=92&start=0&st=0&sk=t&sd=a

Read that thread and download the handy spreadsheet within. In most cases you can write a calibration for a particular NTC/PTC thermistor, then test it and see if an offset is required. Sometimes (low mass thermistors), due to the 1K pullup providing more current to the thermistor making it self-heat, a slight offset is required in the cal.

If you notice adjusting the pullup value changes the calibration curve, if you want better resolution within a certain range you can always switch the temp sensor to an AV channel and provide the custom pullup value externally .

20B wrote:Martin,
Been looking for a 1/8 NPT threaded water temp sensor compatible with M series ecu for a while, any ideas ?

The one in the Motec catalog works great.
Pg 42 Item #8 PN M 25-2197 D US $ 69.22

HTH
Mike

Is this the USA Catalogue?

Yes.