Author Topic: Suggestions for DC current probes (Read 26168 times)

rx8pilot · « **on:** August 10, 2016, 05:41:10 am »

I am hoping to find some suggestions for DC current probes. They are expensive, so hearing some real world feedback may help me avoid an expensive mistake or spending too much.

General specs:
>30Mhz
One low current (5-10A) with low noise.
One medium current 30A continuous.

DIY (if that is even possible) is totally out. I need a proven and reliable probe. Reasonably modern is preferred. I have a Keysight InfiniVision scope so if it interfaces direct that would be great (Agilent/Keysight models). External power supply is totally fine too if it is more affordable or better in technical capability.

The goal is to find a professional tool at a good price, not the cheapest/crappiest/knock-off thing. Hoping someone out there knows of some model that always seems to show up on eBay that would be a good fit.

Thanks in advance......

Someone · « **Reply #1 on:** August 10, 2016, 07:08:15 am »

There are only two manufacturers for these range of high frequency probes, Tek and Hioki. I've never seen the Hioki branded probes for sale but they may be available inside Japan. You will see them available as:
Agilent/Keysight: N2782,N2783 (proprietary but well known interface that happens to match your scope)
Lecroy: CP030,CP031 (proprietary interface, no known adaptions?)

Cheaper and easier might be the indigenous Tek probes:
Tektronix: TCP312,TCP305
They run from a bulky power supply which has a convenient BNC output and are more common than the above probes that meet your edge case requirements.

Current probes for 15A RMS are much more common, and as with all current measurements you can play tricks with impedance and windings to change their response. We make use of "dumb" DC clamps for those higher DC currents you are looking at.

D3f1ant · « **Reply #2 on:** August 10, 2016, 07:16:53 am »

You could consider the Keysight->TEK adapter (N2744A) to open the possibility of using some 2nd hand TEK current probes which are apparently good. I think the Keysight even recognizes them autoprobe style.

Your options are really limited if you don't want a dodgy/semi accurate tool. I decided current probes are too expensive to be tied to a brand of scope so have gone with Hioki on the assumption the probe will be around a lot longer than the scope. TEquipemnt sells Hioki probes so can use the eevblog discount.

The 30A probes require an exernal PSU...so be prepared

ez24 · « **Reply #3 on:** August 10, 2016, 07:26:24 am »

What about a Tek P6021 ? I know it is old but it is NOS (still in sealed bag). I am not sure what it is so I do not know if it fits your needs. It is just the current probe and termination (in bag) with manual. Guaranteed

rx8pilot · « **Reply #4 on:** August 10, 2016, 07:41:49 am »

Thank you. I took a look at the Tek options. They seem like they are more than capable - high frequency and high current. They are a similar price as the Keysight probes. Do you suppose the external amplifier may offer an improvement in low mA measurments?

Hioki makes the Keysight/Agilent current probes?

Sent from my horrible mobile....

D3f1ant · « **Reply #5 on:** August 10, 2016, 07:54:46 am »

Yes Hioki make them for everybody apart from Tek. If you want sensitivity, Hioki make new sensitive 1V/1A models that have not found their way down the rebrand ladder yet.
https://www.hioki.com/en/products/detail/?product_key=5846

ez24 · « **Reply #6 on:** August 10, 2016, 07:57:50 am »

rx8pilot PM sent

tautech · « **Reply #7 on:** August 10, 2016, 08:07:14 am »

Quote from: ez24 on August 10, 2016, 07:26:24 am

What about a Tek P6021 ? I know it is old but it is NOS (still in sealed bag). I am not sure what it is so I do not know if it fits your needs. It is just the current probe and termination (in bag) with manual. Guaranteed

They're AC only and no good at all for DC.

Very good AC current probe even though originally released decades ago still available new but the price is truly shocking ~$3k

rx8pilot · « **Reply #8 on:** August 10, 2016, 08:13:49 am »

The crazy thing is that they seem to hold value. These suckers will melt down a credit card in a hurry. I was hoping there was a little known model that has a lower price, but that does not seem to be the case at all. $2k seems to be the starting line for used.

Sent from my horrible mobile....

nctnico · « **Reply #9 on:** August 10, 2016, 08:15:59 am »

For low voltage I'd go for a current shunt resistor and a differential pre-amplifier so you can make floating measurements. In many circuits using SMD components you'll have to break the loop anyway so connecting a current shunt isn't much different. The reason current probes use hall+transformer is because they are traditionally constructed to clamp over a wire so you don't have to alter the circuit but with SMD that is no longer an option. Also a current shunt is much more precise: 0.1% versus 1.5% or worse for the current probe.

tautech · « **Reply #10 on:** August 10, 2016, 08:38:37 am »

Carlos, Siglent have CP5030, a DC to 50 MHz 30A current probe. It has 2 sensitivity ranges with 1 or 10 mA resolution.
http://siglentamerica.com/prodcut-fjxx.aspx?fjid=4797&id=-1&tid=1&T=1

There's a link to the manual on the page linked above that lists detailed specs for all the models.

List for the one I've mentioned is ~$2600.

chris_leyson · « **Reply #11 on:** August 10, 2016, 08:51:42 am »

LEM make closed loop Hall effect current transducers, bandwidth is only a few hundred kHz, but they use a Hall effect sensor and a feedback winding to null out the DC field. LEM LTSP 25-NP is a PCB mount example. Probably not very practical from a general purpose current probe point of view but they are reasonably accurate.

joeqsmith · « **Reply #12 on:** August 10, 2016, 12:34:19 pm »

What sort of current do you need at 30MHz? Check the derating curves.

For home hobby work, I can't justify spending a lot on one. For DC I too use a few different LEMs, my modified UT210E or a shunt. LEMs
For higher frequencies I have my old modified Tektronix P6042 (DC-100MHzish). For higher currents I use a Pearson. I would guess I have under $100 invested. The Tektronix was non-working when I received it for free. The Pearson came from one of my trips to the Dayton HAM show. The LEMs I have were all pulls. Antique shunts were given to me by an old friend of mine. The UT210E was the high dollar ticket!

rx8pilot · « **Reply #13 on:** August 10, 2016, 05:09:28 pm »

Quote from: nctnico on August 10, 2016, 08:15:59 am

For low voltage I'd go for a current shunt resistor and a differential pre-amplifier so you can make floating measurements. In many circuits using SMD components you'll have to break the loop anyway so connecting a current shunt isn't much different. The reason current probes use hall+transformer is because they are traditionally constructed to clamp over a wire so you don't have to alter the circuit but with SMD that is no longer an option. Also a current shunt is much more precise: 0.1% versus 1.5% or worse for the current probe.

Definitely - I recently purchased two LeCroy 1855A amplifiers for current sense resistor and other uses. Previously, I had a lower performance Tek amplifier and it was my main current measuring tool. The probes would be for parts of the circuit that already have a wire available or a specific test on a section of a circuit.

These are for SMPS design, power monitoring, etc. The slew rate (di/dt) is generally what I am after more than the RMS current which will max out at about 15A. That is what the high bandwidth is helpful for. My next design is using eGan FET's that have very fast edge rates.

Quote from: tautech on August 10, 2016, 08:38:37 am

Carlos, Siglent have CP5030, a DC to 50 MHz 30A current probe. It has 2 sensitivity ranges with 1 or 10 mA resolution.
http://siglentamerica.com/prodcut-fjxx.aspx?fjid=4797&id=-1&tid=1&T=1

There's a link to the manual on the page linked above that lists detailed specs for all the models.

List for the one I've mentioned is ~$2600.

Are those models Hioki as well? Do they need any amplifier or special power supply?

HighVoltage · « **Reply #14 on:** August 10, 2016, 05:23:57 pm »

I have 3 Agilent / Keysight DC current probes

1147B, 15A / 50 MHz
1147A, 15A / 50 MHz
N2893A, 15A / 100 MHz

They all interface directly to the Agilent scope connector and they are recognized by the Infiniivision scopes.
Once in a while you can get lucky with these on the secondary market

I bought two of them broken and repaired them:

https://www.eevblog.com/forum/repair/agilent-1147b-current-probe-%282013%29-repair-need-advise/

And

https://www.eevblog.com/forum/testgear/agilentkeysight-n2893a-current-probe-%28teardown-and-repair%29/

If you have the time to wait, you can get them under $ 1000

rx8pilot · « **Reply #15 on:** August 10, 2016, 06:05:44 pm »

Thanks for those links. I am in no major hurry, so maybe I could wait for a deal or a damaged cable option. Anything under $1000 would be worth some elbow grease.

It would be nice to be have the direct interface for sure.

georges80 · « **Reply #16 on:** August 10, 2016, 06:20:30 pm »

Somthing like -> http://www.ebay.com/itm/Tektronix-TM502A-Power-module-AM-503B-Current-Probe-Amplifier-/112081913785?hash=item1a189a47b9:g:lNEAAOSwtnpXom9R

Don't get the AM503, you want the AM503B.

and a Tek A6302 probe is what I use.

I picked my 'set' up for about $600 for all 3 units (power supply, current probe amp and the current probe).

They work very well and have used them for several years now.

The combination can reliably measure current in the 10mA range and of course is AC/DC measurement capable.

cheers,
george.

HighVoltage · « **Reply #17 on:** August 10, 2016, 06:32:22 pm »

If you want a good general purpose DC current probe, look at the:

Tektronix A622, it is 100A but only 100 kHz
It is made by AEMC, Model SL261
and also sold as Fluke, 80I-110S
or Agilent 1146A

These are really great general purpose current probes, just may be too slow for your applications.

rx8pilot · « **Reply #18 on:** August 10, 2016, 06:37:52 pm »

Quote from: georges80 on August 10, 2016, 06:20:30 pm

Somthing like -> http://www.ebay.com/itm/Tektronix-TM502A-Power-module-AM-503B-Current-Probe-Amplifier-/112081913785?hash=item1a189a47b9:g:lNEAAOSwtnpXom9R

Don't get the AM503, you want the AM503B.

and a Tek A6302 probe is what I use.

I picked my 'set' up for about $600 for all 3 units (power supply, current probe amp and the current probe).

They work very well and have used them for several years now.

The combination can reliably measure current in the 10mA range and of course is AC/DC measurement capable.

cheers,
george.

Is the power supply the TM501 module on the right side of the amplifier? $600 would be amazing! Especially if I could find 2 of them for a similar price. Added those model numbers to the list.

Do you suppose there are any significant performance considerations compared with the more modern probes? Other than the size being a lot smaller - are there any measurement limitations with these that may not exist in the Keysight (Hioki) models?

georges80 · « **Reply #19 on:** August 10, 2016, 07:30:53 pm »

Yeah, the TM5xx is the power supply unit. There's ones with 2 slots and ones with 1 slot. You only need the 1 slot (smaller), but often the 2 slots are all you can find.

I see no advantage with a newer unit (if you have room for the AM503B amplifier). I like that the amplifier lets you get down to low current levels right from the probe output.

Anyhow, like I wrote, I've had my setup for several years (probably near 10) and never had any problems with the unit. I've tested it against known DC current levels and it's 'close enough' to dead on. I use it to test/design LED drivers up to 10A output and the Tek setup works just fine. The 'output' of the AM503B goes straight to any 50 ohm input (no need to worry about tek/agilent 'fancy powered scope bnc's).

I've used it it my older tek scope and now with my agilent scope. Any scope from the last 15+ years allows you to configure a channel for Amp display and set the scaling factor, with that you get direct current display in the appropriate scaled values so no mental arithmetic needed to convert the readings on the scope.

cheers,
george.

tautech · « **Reply #20 on:** August 10, 2016, 09:37:07 pm »

Quote from: rx8pilot on August 10, 2016, 05:09:28 pm

Quote from: tautech on August 10, 2016, 08:38:37 am
Carlos, Siglent have CP5030, a DC to 50 MHz 30A current probe. It has 2 sensitivity ranges with 1 or 10 mA resolution.
http://siglentamerica.com/prodcut-fjxx.aspx?fjid=4797&id=-1&tid=1&T=1

There's a link to the manual on the page linked above that lists detailed specs for all the models.

List for the one I've mentioned is ~$2600.

Are those models Hioki as well? Do they need any amplifier or special power supply?

They come with a wallwart, termination and BNC cable as illustrated in the manual I mentioned you can download.
I couldn't say for sure who Siglent sources them from but I'd doubt it's Hioki, there's other Asian current probe manufacturers that I'm aware of.

rx8pilot · « **Reply #21 on:** August 11, 2016, 01:02:13 am »

Quote from: georges80 on August 10, 2016, 07:30:53 pm

Yeah, the TM5xx is the power supply unit. There's ones with 2 slots and ones with 1 slot. You only need the 1 slot (smaller), but often the 2 slots are all you can find.

I see no advantage with a newer unit (if you have room for the AM503B amplifier). I like that the amplifier lets you get down to low current levels right from the probe output.

Anyhow, like I wrote, I've had my setup for several years (probably near 10) and never had any problems with the unit. I've tested it against known DC current levels and it's 'close enough' to dead on. I use it to test/design LED drivers up to 10A output and the Tek setup works just fine. The 'output' of the AM503B goes straight to any 50 ohm input (no need to worry about tek/agilent 'fancy powered scope bnc's).

I've used it it my older tek scope and now with my agilent scope. Any scope from the last 15+ years allows you to configure a channel for Amp display and set the scaling factor, with that you get direct current display in the appropriate scaled values so no mental arithmetic needed to convert the readings on the scope.

cheers,
george.

These models seem like a great bang for the buck overall. I have enough room for a pair of them on my bench so the size will not slow me down. Unless I get lucky and find an unusual deal on an Agilent model - I believe these are the best fit as they appear to have the performance and a modest price tag. Thank you for sharing your thoughts and experience.

timb · « **Reply #22 on:** August 11, 2016, 01:23:43 am »

Quote from: rx8pilot on August 11, 2016, 01:02:13 am

Quote from: georges80 on August 10, 2016, 07:30:53 pm
Yeah, the TM5xx is the power supply unit. There's ones with 2 slots and ones with 1 slot. You only need the 1 slot (smaller), but often the 2 slots are all you can find.

I see no advantage with a newer unit (if you have room for the AM503B amplifier). I like that the amplifier lets you get down to low current levels right from the probe output.

Anyhow, like I wrote, I've had my setup for several years (probably near 10) and never had any problems with the unit. I've tested it against known DC current levels and it's 'close enough' to dead on. I use it to test/design LED drivers up to 10A output and the Tek setup works just fine. The 'output' of the AM503B goes straight to any 50 ohm input (no need to worry about tek/agilent 'fancy powered scope bnc's).

I've used it it my older tek scope and now with my agilent scope. Any scope from the last 15+ years allows you to configure a channel for Amp display and set the scaling factor, with that you get direct current display in the appropriate scaled values so no mental arithmetic needed to convert the readings on the scope.

cheers,
george.

These models seem like a great bang for the buck overall. I have enough room for a pair of them on my bench so the size will not slow me down. Unless I get lucky and find an unusual deal on an Agilent model - I believe these are the best fit as they appear to have the performance and a modest price tag. Thank you for sharing your thoughts and experience.

If you need a TM501 (single slot) or TM503 (three slot) let me know, I have both, fully restored with brand new caps (major PITA to do) plus I removed the power cord and added a real IEC connector to the TM503.

rx8pilot · « **Reply #23 on:** August 11, 2016, 01:27:40 am »

Do you have the probes or just the amplifier? Does it provide power or is that a separate thing?

rx8pilot · « **Reply #24 on:** August 11, 2016, 01:29:54 am »

I think I figured it out -

The TM501 and 503 are the powered chassis for the AM5xx amplifiers? Is that right?


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Author Topic: Suggestions for DC current probes (Read 26168 times)

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