Can't fail?  Well, the probe itself is a tube with a central rod that makes up a capacitor.  If something conductive gets in between it could short and cause a failure.  Or the termination at the wire could go open.  That's not counting the electronics that converts the capacitance to a frequency.  How to test?  The only way I know of is to get a small capacitor and connect it from the central rod to the shell (without touching anything yourself - not easy).  I've forgotten what the likely value should be, but a 100pf should at least make a movement and a 0.1mfd might be more than full scale.  You might have to experiment a little.  Then look at the output.  I think EI puts a simple cap-frequency converter in the probe itself, so you have to read the frequency with a scope.  Not the kind of test that can be done in the average garage, but it's not that complicated either.

Gary

 

 

EII says probes can't fail.

Sent using my iPhone.
Danny

On May 13, 2013, at 12:31 PM, "William A. Hogarty" <billhogarty@gmail.com> w=
rote:

> Does anyone know a method to test a VM probe in the wing when the wing has=
been removed from the ,plane.