I asked about this on the laser forum, but was advised to bring it here. Before I explain the problem, let me state that my first project was a Tesla coil I built for a science project in the 6th grade. From an ‘gifted’ AM commercial transmitter tube by an amateur radio Elmer. I moved on to fix TV’s (when they actually had tubes in them and hv) and dealt with many fly back transformers. Moving on to some micro wave tubes that had many Kv on them. So I’ve had experience. But, I’ve never built a hv probe… so
I have, or will quickly have, a 50 watt laser that I would like to monitor the high voltage. Everybody monitors the current with a ma meter, as will I. I would also like to monitor the hv.
I have four, 100 meg High Voltage resistors coming. These are the 100.4 series.
Assuming a max of 20kv, I can series ‘stack’ them for 400 meg and that should give me a full scale 50 micro amps, indicating 20kv.
Now for the physical, and the main question, can I stack these in a piece of 1/2" PVC pipe. Secure the hot end connection down in the pipe a 1/2 “, and insulated with some kind of high voltage silicon? At the cold end a simple bolt through the pipe wall to connect to meter. Overall distance from hot end to cold end would be around 10”.
I figure it to be about 1 watt of dissipation. These are three watt devices, so I’m hoping heat won’t be an issue. I thought 1/2 " PVC would be OK based on this dielectric chart showing that this material has a dielectric of a minimum of 10kv/mm. The wall thickness of schedule 80 PVC is about 3.7 mm.
I have seen hv probes that have a neon bulbs wired across the meter and assume it’s for an open meter situation. Could/should I replace this with a zener of some low voltage? I am hoping to be able to put my scope on the meter and get some idea of how the hv is performing…
Thanks for the assistance.