say mates :

I came into a Rotunda timing meter - the lumi probe does not shine light thru it like the Snap On probe for an MT480 - on the greenish side - not sure best how to clean or is I need a new one ( good Luck )

If you can shed some light - appreciate it

cheers in advance

 

you want to use a soft toothpick to clean it with.do not use a solvent.

 

Say FORDF250 :

Done already - improved it a bit - probably 40 % improvement - but no where near as clear as a new Snap On - so I am asking since this probe is a luminosity probe - the intensity of light will effect the reading -

Why I ask specific to the Rotunda - as I have good Snap On probes - if Rotunda used a coloured crystal as to clear

cheers:

 

I have a Rotunda unit as well. My lumy probe is not perfectly clear. It has some fractals in it but I can still see a goo amount of light through it and when installed into the engine, I can see bright flashes from it. Try installing it into the block and if you can see a clear flash coming from it, try the timing.

 

Say Eatont999:

cheers for the reply -

Ok good to hear I quess and I will do so as soon as I am ready - just wondering if this Rotunda would handle one of the Snap On probes - or might it be too bright - as if the electronics are set to only read from a more diffused flash

Rotunda probe head is thicker by 2 mm - ish - so I am sure a Snap On probe could be rigged to fit for temp use - but if the flash is too bright for the Rotunda ........

cheers:

 

I can't say if the two are compatible. I thought the light sensor picked up the flash as a measurement of time, not luminosity, I thought the sensor closed the circuit when the flash is detected and opened it when it is not. This could also be measured by resistance.

 

say eatont9999:

assuming that both your and my Rotunda probes have fractals - and assuming your crystal is not clear - nor is mine ( has a tint , not just from use ) - there would be a reason for this , No?

dunno - just the way I think

cheers:

 

My best guess would a result from the high temperatures and compression of the engine and mistreatment by previous owners. If you drop the lumy probe on a hard surface, like a shop floor, you can expect the crystal inside to crack or fracture. Unless it is really bad, the light sensor should still be able to pick up a signal.

 

Althought the lumy probe doesn't directly measure luminosity in this application, it does provide an intensity signal, which has a threshold level at which the meter detects combustion. Since the combustion is a progression of dark to bright, a probe allowing less light through will reach that threshold later and thus report a more retarded timing.

So although its purpose is just to tell when combustion happens, it does depend on light intensity.

A sensor circuit at this level should not be harmed by low to moderate overload, so the best way to find out is to try the different probes with the same engine and compare.

 

Say NorthernDiesel :

Cheers for the reply - and explaining the process- what I was looking for

will do as you suggest as well as do test with both meters to see if the results match

cheers: