G3X OAT probe cal.

Hey guys! Is there anyway to calibrate the OAT probe on the G3X? Mine seems to be about 8 degrees F too high. Thanks! You are the best!

Where do you have the probe mounted?

OAT probe position

It is out on the right wing lower surface. Just with the aircraft sitting there static the G3X reads 58F and the actual is 50F. Also ice seems to form on the wings before the G3X reads 32X.

n700jl said:

It is out on the right wing lower surface. Just with the aircraft sitting there static the G3X reads 58F and the actual is 50F. Also ice seems to form on the wings before the G3X reads 32X.

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Hello Jon,

The GTP 59 is a very high accuracy TSO'd RTD type OAT probe that doesn't require any calibration. These probes generally either work and work well, or they don't.

I suppose this static reading is in the shade of your hangar where there isn't any pavement heating going on which might influence the air temperature under the wing?

When I power up my avionics in the hangar in the morning I have pretty amazing correlation between OAT, oil temperature (also high accuracy RTD probe), and all the high sensitivity type J CHT probes. The higher range type K EGT probes even agree pretty well.

With everything cold and at ambient in the hangar, how do the oil temperature and OAT probe readings compare?

Thanks,
Steve

Another thing to do is to check for loose or dirty connections all throughout the circuit that connects the GTP 59 to the GSU 73, especially the ring terminal at the base of the probe body. This type of temperature probe is simply a precise resistor whose resistance changes with temperature in a predictable way. Just a few extra ohms can cause a significant temperature offset.

- Matt

Thanks

Steve,
I let everything stabilize in the hanger overnight. The EGT and CHT's were dead on 50f and the OAT was on 52f. I will check the ring terminal and see what happens. Thanks for the quick response.
Jon

n700jl said:

Steve,
I let everything stabilize in the hanger overnight. The EGT and CHT's were dead on 50f and the OAT was on 52f. I will check the ring terminal and see what happens. Thanks for the quick response.
Jon

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I was suspicious that my probe was reading High also. Walked into the hangar and fired up the G3X and had solid 60 degrees on all CHT's and EGT's but 62 on the OAT. Removed the probe and scotchbrited the metal under the ring terminal and will check again tomorrow.