GRT EIS Oil Temp Probe Specs

Hi,

We are just into our flight testing and are getting high oil temp levels whilst the oil pressure still seems really 'normal'. Removing the oil temp probe isn't trival, but measuring the resistance is.....

Does anybody know the specs for the resistance / temp curve for the GRT EIS Temp Probe - GRT Part # FT-LC-01

[ I've got the question in with Greg @ GRT, but it will probably be Tue Morning NZ time before I get to see an answer ]

Thanks in advance,

Carl (still grinning!)

Does it measure correctly when the engine is cold and at the know room temp?
Danny

Hi Danny,

Yes - Room temp seems sensible and removing the probe and boiling water test is on the list - I just wanted to make sure the display device in the equation was working correctly first (simplist test), I can measure the resistance between ground and sensor - what I need is the probe spec.

Cheers,

Carl

If anybody has the resistance for temp curve specs for a GRT FT-LC-01 oil temp probe, I could make good use of the numbers.

Thanks in advance,
Richard

I believe the sensor is an ntc thermistor but I don't know the Ro and Beta parameters for the actual sensor.

Ro (or resistance at 25 deg C) - this is 10k ohms for the oat sensor and may be the same of the oil temp sensor. Try measuring the sensor at 25c ambient to estimate this. Alternatively replace the sensor with a 10k ohm resistor and see what the EIS indicates, if it is 25c then you have the Ro value.

The beta value is likely to be somewhere in the range 3700-4100.

The resistance of an ntc thermistor is Ro x e^(Beta x ((1/T) - (1/To)))
where To is 25 ( deg c).

Use a second resistor value in place of the sensor, read the EIS temperature. Then solve for the Ro and beta.

Easier to do than describe, junior school maths.

Report back on your findings.
Doug Gray

Your oil temps will run higher during initial break-in. What is your high temp reading?

Check sump temp as soon as you shut down with an infrared thermometer. Watch out for hot exhaust. It should be very close to EIS reading. All of my cht, egt, oat and oil temps are all within 1 degree of each other sitting in the hangar.

Whenever I installed anything electrical on my plane I measured everything I could and recorded it(voltage, amperage and resistance). Every third or fourth flight I record all measurements on my panel. If you have problems down the road this helps in troubleshooting.

Thanks Doug,

3 sources have the OT sensor at 10K @ 25C. The sensor and engine are fine. I am just calculating ADC(analog to digital conversion) values to use the existing sensor with an Extreme EFIS that is being expanded to engine monitor. The EGTs were plug and play. The oil temp allows for several pre programed curves for various makes and types sensors. MGL also allows for your own custom calibration if a sensor not in the menu is used.

In case it helps others, the numbers for the GRT FT-LC-01 oil temp probe are:
25 C =10K Ohms
50 C =3601
60 C =2487
70 C =1752
80 C =1256
90 C = 916
100 = 678
120 = 388
140 = 234
150 = 185

Now to get the ADC values right...