Calibrating Oil Temperature sensor

[cbretana]

Is there any way to calibrate the oil temperature sensor to make sure it is sending the right signal to the EMS? Also, I have been told that single wire oil temperature sensors (that use the engine crankcase as pathway to ground) are frequently unreliable due to ground loops and that two-wire sensors are to be preferred. Is the two-wire GRT sensor (GRT LC-FT-01) compatible with the Skyview EMS (SV-EMS-220), and if so, does it need to be calibrated?

Thanks!

 

[Marc_J._Zeitlin]

Is there any way to calibrate the oil temperature sensor to make sure it is sending the right signal to the EMS? Also, I have been told that single wire oil temperature sensors (that use the engine crankcase as pathway to ground) are frequently unreliable due to ground loops and that two-wire sensors are to be preferred. Is the two-wire GRT sensor (GRT LC-FT-01) compatible with the Skyview EMS (SV-EMS-220), and if so, does it need to be calibrated?

The OT sensor can't be "calibrated", but it can be checked - just did exactly that on the single wire sensor on a Long-EZ this morning. Heat up a pot of engine oil to 300F and buy a candy thermometer (be VERY careful - the last thing you want to do is spill 300F motor oil on you or your airplane). Connect the sensor (single or two wire) to the engine wiring (and ground as necessary) and put the tip into the pot of oil, along with the thermometer. Watch the temperature values as the oil cools and see how much they vary. The one we tested was within a few degrees of the thermometer from 260F to 190F. I've had one (12 years ago or so, on my plane) that was 30F - 40F off (high) when around 210F (read 250F). Nothing for it but to buy another sensor.

While the single wire sensors are more sensitive to grounding issues, if they aren't jumpy and unreliable, they work just as well as the two wire sensor. That said, I recommend the GRT sensor just because you don't ever to worry about grounding issues. And yes, they're compatible with the EMS-220 (I've got one on my plane) and as stated above, there's no calibration - just a test, if you think there's an issue.

 

[RaymondJ]

For what it's worth (and for the ability to potentially salvage really annoying sensors that can't be replaced / rewired), it's possible to "calibrate" the sensor by writing a custom sensor definition with a new voltage->temperature curve. Not something I'd reach for as a first solution (since a sensor going out of spec like that probably means it's dying in some way), but a good tool to have at the bottom of the toolbox.