Current Probe Calibration, DIY 1:100 Amplifier [SOLVED]

[HighVoltage]

I am working on a design with a few different dimensions.

- One with smaller wires to accommodate the smaller opening of the Keysight probes (1147B) and
- One with heavier wires for the larger probes.

[PTR_1275]

I'd be interested to see your design. I really like the transmille one with its 3 different coils.

I don't have a current reference so my accuracy is not going to be anything great, but having a better way of checking clamps at higher currents would be nice.

I was honking of putting a DPDT switch in mine so that I can make the current flow one way or the other for checking the difference between positive and negative currents easily.

Once again, I'm only thinking about DC at the moment, but would be interested to see how well it goes on AC and how to test for any problems.

[HighVoltage]

Here was my first attempt for a simple design for 20 loops of 2.0mm diameter copper wire.
Just two of the same parts, mounted together
- The inner opening height will be 24 mm.
- The tube diameter will be 10 mm with a 8mm hole in it
- Material: Black PE
I think I will just place an order in the machine shop and see how good it works and then improve on it.

This one is for the larger current probes and will not fit the Keysight 1147B

[bopcph]

Its funny, I've been working with the Tektronix AM503 / A6302 setup some years ago, and my experience is that they are quite accurate.

A well maintained and calibrated AM503/A6302 will easily give you precision within the limits of your scopes precision and 1-2% on your HP34401 - within the ACV limits of the 34401, crest and frequency.

We used it for work on SMPS, invaluable !, from a few kHz/100mA to 20Amps at 500kHz with risetimes that indicated well over 15MHz (fundamental) - all within 1-2%.
Remember to terminate it with 50ohms, remember to degauss, don't through it on the floor, don't use it as a hammer, don't chew on the cable, don't use it as a wrench - do I need to say more?.

Seeing how many questionable (spare)parts available on eBay inspired me to the list above 

Just handle it like you would your crystal champagne glass, those you only use for special occasions - you don't through your HP3458A on the floor a few times a day either do you - and would you trust it with more than a handfull of digit if you did ?   

[HighVoltage]

Its funny, I've been working with the Tektronix AM503 / A6302 setup some years ago, and my experience is that they are quite accurate.

I think I have a Tektronix A6302 or similar (by the looks) in a drawer without the amplifier, directly to BNC
This one might has the smallest opening of all, so I need to make my design for the amplifier to fit that probe.
Thanks for that reminder!

I have never used the AM503 amplifier, may be something to look in to.

[capt bullshot]

Its funny, I've been working with the Tektronix AM503 / A6302 setup some years ago, and my experience is that they are quite accurate.

I think I have a Tektronix A6302 or similar (by the looks) in a drawer without the amplifier, directly to BNC
This one might has the smallest opening of all, so I need to make my design for the amplifier to fit that probe.
Thanks for that reminder!

I have never used the AM503 amplifier, may be something to look in to.

If it has a direct BNC connector, it's not the P6302/A6302. It's an AC probe, they look quite the same as the P6302 but don't have the hall element for the DC path. Maybe it's an http://w140.com/tekwiki/wiki/P6016 or the like, they can be used with a passive terminator.

[macboy]

Its funny, I've been working with the Tektronix AM503 / A6302 setup some years ago, and my experience is that they are quite accurate.

I think I have a Tektronix A6302 or similar (by the looks) in a drawer without the amplifier, directly to BNC
This one might has the smallest opening of all, so I need to make my design for the amplifier to fit that probe.
Thanks for that reminder!

I have never used the AM503 amplifier, may be something to look in to.

The P6019, P6020, P6021, P6022 probes have a BNC connector. Note however, that these all require one of the following: Its own special passive terminator/compensation box, or an external amplifier (e.g. Tek model 134), or a dedicated scope plugin (e.g. Tek 3A9 or 7A14). The probe must never be operated without one of those terminations. Plugging it directly into a 1 MOhm scope input will not terminate the current transformer secondary properly and high voltages can result, damaging the transformer and/or scope.

I have two P6021 probes, one with the passive terminator and one with a model 134 amplifier. The 134 amplifier gives better sensitivity and extends the low frequency response significantly (from 450 Hz to 12 Hz) but reduces the high end a little (from 60 MHz to ~50 MHz). One of my P6021 probes has the extra long cable option which reduces the bandwidth quite a bit.

The 134 amplifiers are plentiful on ebay.

[HighVoltage]

Thanks for the feedback on the Tek probe.
Yes, it is a P6022 it came with a proper terminator.
It is a really need little probe, just too bad it is only for AC

I think I should look for the 134 Amplifier but only see 110V versions on ebay.
Can the 134 amplifier be rewired inside for 230V?


 

[dl1640]

Here is 9100 calibrator coil, this paper is from Fluke UK

I have both this coil set and 5500 calibrator coil at work,, but both do not fit some probe clamp
Also inductance will hard to drive for higher current, on 5500 series calibrator we need to enable LCOMP
which is degrading the accuracy according to the document

I need a 100 turn coil to simulate 500A at DC and 50Hz but home made one is difficult to determine the uncertanty, but worth playing..

[HighVoltage]

Thank you dl1649, that is a very interesting paper.

Building a current amplifier like this is not as easy as I first thought.

[dl1640]

Anyway, use the x turn coil is easy to check full range of clamp meter and usually they are not so accurate device.

So maybe we can use a thru-hole CT with very good linearity and wind your coil onto it to make a fixture and calibrte them as one,
then we can calibrate clamp meter more accurately.

[tautech]

Thanks for the feedback on the Tek probe.
Yes, it is a P6022 it came with a proper terminator.
It is a really need little probe, just too bad it is only for AC

I think I should look for the 134 Amplifier but only see 110V versions on ebay.
Can the 134 amplifier be rewired inside for 230V?


 

These P6021 and 22 probes are gold, please treat them as such.
The 134 amp has an external supply.....wallwart if you like. Two versions, the 110VAC is easy to find, sadly the 234VAC not so much. The Tek part # on one I have is 015-028 and I luckily got it from member whitevamp who found a box of old Tek stuff.
Not sure if he's got more.
https://www.eevblog.com/forum/testgear/unknown-tektronix-part/
https://www.eevblog.com/forum/buysellwanted/fs-us-misc-tek-parts-and-fairchild-voltage-regulator/msg1113899/#msg1113899

[HighVoltage]

My first attempt to build a 1:20 Amplifier with this small 80 mm diameter holder just failed miserably and looked horrible.

I had no idea, how difficult it can be to get 2mm copper wires through such an opening, although in theory it should fit perfectly.

So, I started over with 1:10 and that works well to get 10 loops through the 8 mm hole.

Next is to scale it it up for 1:20 
And may be eventually 1:100, will see...

[dl1640]

So cute, I like it

[HighVoltage]

Continuing this project, I got some coils professionally built with 50 turns of copper wire as close together as possible. These insulated copper windings are forced glued during the winding process and stick together, as if they are one piece.

This is a rectangular shaped coil that I potted with epoxy in to a little holder and built an adapter box for the connection around it.

It works surprisingly well and could hold 4 of these Keysight/Yokogawa current probes together.

Here are the first test results.
 

[HighVoltage]

The 50 windings are small enough to accommodate the very small opening of the Tektronix P6022 probe.

[HighVoltage]

If anyone is interested, I have some spare parts of the copper windings, already epoxy potted in to the little holder with some short cables attached. All tested and working perfectly.

2 x 50 turns
1 x 59 turns

Euro 10 each plus shipping, send me a PM.

=====================
Edit:
Both 50 turns coils are gone.

[HighVoltage]

And here is a test with a pulse current to take the FLUKE 80i-110s to its limit of 100A,
within a pulse length of 90 μs and a primary current of 2A

[HighVoltage]

With a sine wave input of 1V RMS , the amplitude stays stable until about 1 kHz and the -3 dB point is at 26 kHz.
Here is a picture of a sweep from 1 kHz to 26 kHz.