Avionics expert needed.

[johnM]

hi

thanks to you all for your help on this matter. Recently a friend of mine put an oscilloscope on the oil pressure sender output and we discovered that there are indeed spikes in the oil pressure. I then contacted Conrad Beale and discovered that Rotax are aware of this problem and have been working on an alternative oil pressure relief valve, which seems to be the source of the problem. It has only come to light with the introduction of digital monitoring systems.
MGL EFIS's ( and Dynon I believe) do not have any damping inside. At present I have managed to damp the oscillations considerably by putting a capacitor on the oil pressure input to the RDAC. Hopefully I will find the correct size to eliminate them entirely.
The fluctuating water temperature reading turned out to be caused by a loose connector onto the engine. As for the complete failure of all the readings for five minutes, I am at a loss to explain it.

My advice to others who suffer oil pressure reading fluctuations is to try to get hold of an oscilloscope( off ebay if necessary) as I found that a digital multimeter did not show the problem at all. I was told by many that I must have an earth loop issue when in fact I did actually have fluctuating pressure.

Once again, thanks for all your help
John

[bertdeleporte]

Happy end,

thanks for feed-back, as often, the trick was not where expected, and a combination of different problems (oil pressure fluctuation + one loose connector) blured the scheme and did give clues thinking of a different cause than it was.

Very glad for you,

Bertrand