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Fluke high voltage probe 80k-40

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hen918

Thu Jul 14 2016, 04:35PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Test results at high voltage would be a much better representation of its true performance.

Patrick

Thu Jul 14 2016, 06:36PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

hen918 wrote ...

Test results at high voltage would be a much better representation of its true performance.

I think the best solution is to build a 1kHz square wave 3kv source, and see if you get a saw tooth pattern, and how bad it is.

Physikfan

Thu Jul 14 2016, 09:33PM

Registered Member #60240 Joined: Mon May 16 2016, 07:01PM
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Posts: 304

Hi Patrick and hen918

"I think the best solution is to build a 1kHz square wave 3kv source, and see if you get a saw tooth pattern, and how bad it is."

I would like to do such experiments.
Please, could you give some hints from where I could get such a 1kHz square wave 3kv source?
A sine wave generator with a fast high voltage amplifier could also do the job?

Regards

Physikfan

Patrick

Fri Jul 15 2016, 08:49AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

You will have to build this device, or go to a nuclear weapons development laboratory, like Los Alamos.

Langston

Thu Oct 18 2018, 09:33PM

Registered Member #64776 Joined: Mon Sept 10 2018, 12:43AM
Location: FL
Posts: 2

Hello Everyone:

I'm new to the forum and found it via a search on the HV probe discussed in this thread. This thread was quite helpful in my purchasing decision, thus I'd like to return the favor a bit with the following. Hope it's OK given the the age of the thread. :)

Fluke doesn't publish bandwidth specs, but it's clear this thing is primarily intended for DC to 50Hz/60Hz power line applications.

One important aspect of this probe is that it's designed to be terminated with 10MÎ© as is expected from most multimeters. Since scopes have 1MÎ© inputs, I added a 10:1 probe with the required 10MÎ© input impedance in series with the Fluke probe and connected that to a Picoscope 200MHz scope running the FRA dual channel FFT Bode plot software. This software uses the Picoscope's built-in waveform generator that has a maximum 4V pk-pk output. The resolution selected was 10 tone bursts per decade.

The first plot I show is a loopback of the 10:1 probe and FLC A400D amplifier (400V max, 20x gain, <0.1Î© Output Z, DC to > 1MHz). The amplifier is the cause of the bandwidth roll off above 2MHz.

The second plot is the addition of the Fluke probe driven by 80V pk-pk from the amplifier. It's down slightly at 60Hz and hits -3dB around 280Hz.

So now I know what Fluke should have included in the specs from the beginning: the 80K-40's bandwidth is DC-280Hz. You'll have to use a different HV probe if you want to look at harmonics.

1539898284 64776 FT177213 10x Probe A400d

Patrick

Sun Oct 28 2018, 09:50PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Langston wrote ...

well this pretty much settles it. though 4 V is a bit low to test with. still i think 200-300 Hz is credible. a bode and gain phase plot is what we need for this kind of thing.

866rectifier

Mon Oct 29 2018, 12:55AM

Registered Member #64743 Joined: Sat Sept 08 2018, 07:41PM
Location: Canada
Posts: 9

I reverse-engineered a Pintek DP15K Differential HV probe 15kV 35MHz bandwidth.
It uses a 15MEG 1W 10kV Vishay VR68 resistors for each (+) and (-) input.
For HF compensation, a 2k in series with three 1,000pF caps, to give 333pF+2k parallel to each 15MEG.

My point is I think you need many pF at 40kV-rating across the gigohm resistors to get better frequency response.

Patrick

Mon Oct 29 2018, 04:36AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

so the lower the divider resistance the greater the capacitance compensation needed ?

I was thinking of getting one of these :

i need it for this and SMPS feedback loop design. But its expensive.

johnf

Mon Oct 29 2018, 06:17AM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

IMHO
resistive only high voltage dividers are low frequency only.
At work we parallel a capacitive divider with the resistive to match the DC characterisitics to the AC. Knowing your frequency you can set each divider up as equal ie the AC divider matches the DC at that frequency ---easy to get 0.1% accuracy ---but this is only at this one frequency with inaccuracies climbing as you move away from that.
a true AC only divider uses lossy capacitors to give broadband response ie series caps get series resistance as well to damp and parallel C's get parallel R for the same damping. Then if above 20kV field shaping (corona rings) becomes important to keep corona losses from causing inaccuracies

Langston

Mon Oct 29 2018, 04:02PM

Registered Member #64776 Joined: Mon Sept 10 2018, 12:43AM
Location: FL
Posts: 2

Patrick wrote ...

well this pretty much settles it. though 4 V is a bit low to test with. still i think 200-300 Hz is credible. a bode and gain phase plot is what we need for this kind of thing.

Hi Patrick:

Actually, the FLC A400D amplifier I used downstream of the 4V pk/pk function generator provided a 20x gain for an 80V test voltage.

That's still quite a long way from the voltages this probe is designed for, but it's the highest voltage I could arrange with a known flat transfer function and low impedance output. I did try 4V straight from the generator and got a similar response BTW, but the transfer function traces were very noisy as you can imagine given the probe's 1000x voltage divider. :)

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