At the lab, there is a smoke chamber and it has a photo tube.
This is this problem, for what ever reason the lab has 0 documentation of the electronics and the service tech they tend to use for calibration does not know any more.. All he knows is what it suppose to be at the end of the anode with a 1MEg load on it, which is 0..5V ..
Ok, all that is just fine however, there is some confusion about the voltage requirements for this tube, of course, we can't find any spec's on that either.
In any case, after looking at generic photo multiplier tubes and circuits it appears that -600DC at the cathode seems to allow this to work ok when we calibrate for dark current. We need the tube to have some linkage at dark current so when the filter is applied we have a detectable view of the smoke.
Does 600V sound about right?
The calibration tech seems to think it should be down around -350VDC which works fine for a clear view but has a drop off so the filter view has very low sensitivity, which makes perfect sense to me since the tube needs to be ionized to get some leakage.
We do have photo multipliers in use elsewhere however, those supplies are up around 1kVDC and that we do have proper specs and design work but they are a much larger tube, the supply in the smoke chamber unit can only output up to -700DC.
What's your take on this voltage scale?
Jamie