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Dorsal
02-22-2012, 01:13 PM
Does anyone know where I can find the resistance vs temp curves for the Rotax oil sensor? I'm still trying to debug some erratic and high oil temp readings on my Dynon.

Av8r_Sed
02-22-2012, 05:19 PM
Dorsal,

This link has information that may be helpful, but isn't exactly what you're looking for. http://www.bullyhawk.com/troubleshooting-rotax.pdf

-- Paul

HighWing
02-22-2012, 08:08 PM
I don't know if this will help. I have always used the Westach gauges and their temp sensors were failing fairly regularly so I decided to try to make my own. I buy a lot of stuff from Mouser and on their thermister page(s), they give the resistance value at 25° C. By measuring the resistance at that temp, I was able to find an off the shelf thermister that I was able to pot into the original brass housing. This worked for me as I thought that the internal parts were likely off the shelf components and should be available somewhere. My home made units worked fine. My theory is that Westach uses heat shrink to insulate the wires in the brass housing before potting and that vibration is sufficient through the heat shrink that it can damage the soldered connecion to the thermister. The ones I made avoided the heat shrink and were potted directly to the wire and lasted many times longer than the factory ones.

This doesn't answer your question about resistance vs. temps on a chart, but it might help. It is interesting that the thermister I needed had a somewhat interesting resistance at the standard temperature. Where the bulk of them had resistances in typical even numbered increments - 100, 200, 1K, 2K ohms, etc., the one I needed (2.786K) was right there.
Lowell

Dorsal
02-26-2012, 04:03 PM
Thanks for the responses, I did find the critical piece of information that I needed which was that the resistance varies inversely with temperature, I had been looking in the wrong place for the problem.