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Beckman high voltage probe 231-22

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Physikfan

Tue Jul 12 2016, 01:33PM

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

Hi

This Beckman high voltage probe 231-22 should be used with a dc voltmeter with
an input impedance of 22Mohm.
The probe extends the voltage range up to 40 kV dc and has an input impedance of 1 GOhm.
Inside this probe is a 1000:1 voltage divider.

Beckman2Banane400x181

Accuracy: (HV231 -22) DC Volts Â± 1 % (1 kV bis 20kV),
Â± 2% (20kV bis 40kV)

Please,
1. who has done high voltage measurements with this and other high voltage probes?
2. what is to say about the performance of such probes?

Regards

Physikfan

Patrick

Tue Jul 12 2016, 06:40PM

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

Please,
1. who has done high voltage measurements with this and other high voltage probes?
2. what is to say about the performance of such probes?

1. Me.
2. The higher the impedance/resistance, the more garbage you get from an other than perfect DC source. 1G ohm is very high, uA and nA can be sabotaged by any little change in the environment.

40kV / 1G ohm = 40uA thats a very weak signal. then it goes into a high resistance DMM (10M ohm).

What exactly are you interested in measuring ? I spent years asking your same questions, and found the end purpose to be more important than most of factors.

Physikfan

Wed Jul 13 2016, 08:03AM

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

Hi Patrick

1. I have to build up a Cockroft-Walton circuit and a Marx-generator, voltage as high as possible with limited resources.
2. I am working on IGBT based electronic interrupters for big induction coils,
spark length as high as possible but on the other hand NOT to destroy the secondary coils of these generally very old instruments.
3. I would like to develope some procedures to check the electrical conditions of such old induction coils.

The main pupose of this work on these high voltage probes was:

1. to check the function of my test possibilities and also
2. to get an overview which items are more reliable compared to others and finally
3. which measurements with finally selected instruments seem to deliver reliable data

The work on these high voltage probes could be divided in:

1. high voltage probes with no frequency compensation like Fluke, Beckman, Coline, etc.
2. high voltage probes with frequency compensation like TEK 6013, 6015, 6015A, etc.
3. Using large resistors as a part of voltage dividers like Leybold 30GOhm for 300 kV DC for 10MOhm impedance voltmeters, etc.

Regards

Physikfan

Patrick

Wed Jul 13 2016, 06:22PM

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

in the case of a CW multiplier i think option 3 is best.

I think thats what this was meant for.

Physikfan

Thu Jul 14 2016, 09:25PM

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

Hi Patrick

Here are the results of preliminary measurements of the frequency dependence of the Beckman high voltage probe 231-22 at 10 Hz, 30 Hz,
100 Hz, 300 Hz, 1 kHz, 3 kHz, 10 kHz, and 30 kHz.

Equipment: HP function generator with an output voltage of 30 Vpp, Tek 7854, 7A22 and 7A26.

The output signals of the high voltage probe are shown in the next pictures (7A22, 2mV/div).
To eliminiate all kinds of electrical noise as far as possible the external trigger of the oscilloscope was used to add up
the small signals one hundered or one thousand times with the right phase:

Beckman2F10Hz400x358

11mVss

11 mVss

10 mVss

7 mVss

2 mVss

2 mVss

2 mVss

etwa 2 mVss

From the frequency of 1 kHz and above these signals remain constant at about 2 mV.
Due to the not shielded cable between probe and scope these signals are presumably caused by electrical noise.

From this dataset the frequency dependence can be determined.

Regards

Physikfan

Patrick

Sat Jul 16 2016, 12:03AM

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

I think you're seeing the limits of the probe, and it will only get worse.

Heres some of my previous work, an HEI coil given a single low voltage pulse.

(EDIT: from tough to trough is 178uS)
I only tapped a 9V battery to the HEI iggy and captured this waveform...
5.08 Kv peak, 800 volt ring below ground. 254 uS for the main pulse (i think) 1/0.000254 = 3937 Hz, i think thats close to its resonant freq.

The probe is only expected to work up to 100Mhz, the math in the simulation tries to go perfect towards 10GHz which obviously wont happen in a real device. but this work of Turkey9 was important, it really saved me, and lets me make another better one sometime.

Turkey9 helped me a great deal this graph is important:

Turkey9 wrote ...

Well looks like I made a mistake in the simulation. I forgot that in Spice M is the same as m so the plots I posted before were with 125 miliohm resistors! Oops!

I redid the sim with the right values and got a very different plot. There is still something interesting, however. The plot below is to 10kHz and stays completely flat all the way past 10GHz. The low frequency is interesting though.

Sorry for the error!

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