measuring high voltage with spectrum analyser

[fonograph]

Conrad Hoffman,in my last post I explained that fundamental is only 12MHz and that my requirment for 100MHz was out of desire to see harmonics.Yes I would now write MHz and mHz properly 

The more I think about using non contact method,the more attractive that options becomes.At 12MHz and 4 thousand volt,like you said the field around should pretty strong,I am noob so I wonder,if I do the non contact method,how is it going change the measurement? For example,how different will freqency response be than if I measured directly? Is it going to be shifted?

Becose I know low freqency AC radiates less photons than higher freqency AC,so the 12MHz fundamental wouldn be displayed lower and high harmonics at 100MHz higher relative to their true amplitude? Is this done capacitivly or using radiowaves/photons or magneticaly by induction? How much harmonic distortion and noise would this non contact method cause,more, or less than HV probe?

[PartialDischarge]

Regarding the mentioned derating of these resistive HV probes I've opened a new thread, as I've always been curious about that graph...

https://www.eevblog.com/forum/projects/tek-high-voltage-probes-derating-with-frequency/msg1207712/#msg1207712

[w2aew]

Conrad Hoffman,in my last post I explained that fundamental is only 12MHz and that my requirment for 100MHz was out of desire to see harmonics.Yes I would now write MHz and mHz properly 

The more I think about using non contact method,the more attractive that options becomes.At 12MHz and 4 thousand volt,like you said the field around should pretty strong,I am noob so I wonder,if I do the non contact method,how is it going change the measurement? For example,how different will freqency response be than if I measured directly? Is it going to be shifted?

Becose I know low freqency AC radiates less photons than higher freqency AC,so the 12MHz fundamental wouldn be displayed lower and high harmonics at 100MHz higher relative to their true amplitude? Is this done capacitivly or using radiowaves/photons or magneticaly by induction? How much harmonic distortion and noise would this non contact method cause,more, or less than HV probe?

4KV is nothing to fool around with if you are a noob, mistakes can be fatal.

Non-contact sensing is certainly safer. It won't change the voltage at your device, and frequency response will be a function of the near field probe / antenna. Since you're dealing with high voltage, low current, the near field energy will be dominant an E-field, thus you'd want to use an e-field probe.

Here's a video I did on near field probes.

[fonograph]

that was excellent video! I instantly subscribed,I hope your ankle is healed.These sniffer magnetic and e-field probes seem perfect,how is the noise and distortion performance when you use these instead of directly probing? Who makes the best sniffer probes?

[Zero999]

The more I think about using non contact method,the more attractive that options becomes.At 12MHz and 4 thousand volt,like you said the field around should pretty strong,I am noob so I wonder,if I do the non contact method,how is it going change the measurement? For example,how different will freqency response be than if I measured directly? Is it going to be shifted?

Yes, go with the non-contact method. When you're in the near field (<<¹/₄ wavelength), you can make the assumption that a metal plate, placed near what you're measuring is just a capacitor in series with it. If you know the area of the plate/wire and the distance, you can easily work out the capacitance.

I'm a bit confused about whether you're measuring voltage or current? 4kV is easy to measure with non-contact methods but 1mA is much more difficult.

Becose Because I know low freqency frequency AC radiates less photons than higher frequency AC

Not quite. The amount of photons is the same, it's just that lower frequencies generate low energy photons, which are much more difficult to detect individually than high energy photons.

[tautech]

that was excellent video! I instantly subscribed,I hope your ankle is healed.These sniffer magnetic and e-field probes seem perfect,how is the noise and distortion performance when you use these instead of directly probing? Who makes the best sniffer probes?

Here's a thread that should give you some guidance:
https://www.eevblog.com/forum/testgear/new-affordable-emc-probe-set-at-a-bargain-price-from-ariel-rocholl's-lab/

[Molenaar]

The more I think about using non contact method,the more attractive that options becomes.At 12MHz and 4 thousand volt,like you said the field around should pretty strong,I am noob so I wonder,if I do the non contact method,how is it going change the measurement? For example,how different will freqency response be than if I measured directly? Is it going to be shifted?

Yes, go with the non-contact method. When you're in the near field (<<¹/₄ wavelength), you can make the assumption that a metal plate, placed near what you're measuring is just a capacitor in series with it. If you know the area of the plate/wire and the distance, you can easily work out the capacitance.

I'm a bit confused about whether you're measuring voltage or current? 4kV is easy to measure with non-contact methods but 1mA is much more difficult.

But wouldn't a near field measurement load down the source too much for a reliable measurement, since in this case both the frequency and the source impedance are quite high?

[Hensingler]

But wouldn't a near field measurement load down the source

The OP doesn't have a 4kV 12MHz source and never will. This whole thread is ridiculous.