I am trying to monitor a HV circuit and isolate it at the same time. I am kind of limited with scraps parts I have lying around. I have box of 1:3 transformers. The original feedback is just a series of resistors to bring the HV down to MCU level voltages. I tried putting a 1:3 transformer flipped around, between two 1M resistors, and it worked, but the issue is that when I swap out to a different transformer in the box, the voltage deviates a lot on some of them. I am guessing that the those 2 1M ohm resistors really limit too much current?

 

Monitor its voltage, its presence, its current ? AC or DC ? 1KV, 10KV, 100KV ...?

 

Happy to help IF we know the HV you're measuring. Just starting off, I'm assuming your HV is AC, not DC. But lets assume you're running 500VAC and want to measure it. With two 1MΩ resistors in series forming a voltage divider your voltage would be 1/2 the source voltage (the 500VAC). The amount of current the two resistors are drawing is Voltage divided by Total Resistance. In this example, 500 ÷ 2,000,000 = 0.000,25A (or 250µA) That's almost nothing. As far as affecting the circuit - I wouldn't worry about it. As long as it's only providing a reference voltage for measuring the output.

 

Yeah, it is AC. It can be anywhere from 100VAC to 500VAC @ 15kHz. I was trying to use it to see what the exact Voltage was, but that does not seem feasible with the huge variance, so it will probably just be presence detection for now. I wanted to do presence detection with an optocoupler, but I do not have one in house.

 

Regular transformers don't work well with 15kHz. They're typically designed around 50 ~ 60Hz.

 

Regular transformers don't work well with 15kHz. They're typically designed around 50 ~ 60Hz.

It's an audio one.... MET 39

 

Perhaps ?

----> https://www.amazon.com/10-Light-100...2?keywords=neon+tester&qid=1643652098&sr=8-12

----> https://www.amazon.com/KAIWEETS-Sen...words=neon+tester&qid=1643652098&sr=8-30&th=1

Once upon a time, I bought a multimeter and decided to test it at my workplace against an AudioPrecision reference instrument. It was accurate to 20KHz. So I adhered a chart on its back referencing VAC <---to ---> dBu. Still have it and has served me very well.