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Accurate Low Amp Current Probe Advice

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KungFuJosh:
What do you recommend for a decent accuracy low(ish) current probe? I want something that has good accuracy in mA range and up to 5A (though I probably won't probe anything over 2A, so 2A or 3A is fine, whatever). Needs to cover AC and DC.

Also, hopefully not insanely expensive. Ideally, I'd like something under $500. Used is fine. If somebody has something awesome they want to trade for my 3532-50, PM me. 😉

Most common use would be tube guitar amp stuff, which mostly ranges in the low mA, but heater current might be significantly higher in the 1.5A level. Also my FUtracer tube curve tracer, but that's mostly the same levels. So 5A is overkill.

I understand there are other ways to measure this, that's not the point. I want to see things on the scope screen for fun, not due to any necessity.

Thanks,
Josh

thm_w:
Any bandwidth requirement?

https://www.eevblog.com/forum/beginners/current-probes/
https://www.eevblog.com/forum/testgear/micsig-cp2100b-current-probe/
https://www.eevblog.com/forum/testgear/which-dso-current-clamp-to-buy/

KungFuJosh:
Not really any BW requirements. Some stuff is DC, and most of what I would be testing are audio circuits.

The power tubes I use are probably going to run between 20mA and 100mA, and those are more important than the preamp tubes that might only see .5mA to ~1.5mA on the plates.

I've already read a lot of threads and opinions on here, but mostly it points to the common recommendations being poor subjects for low current readings. The CP2100B was one I was curious about, but that apparently sucks in the low mA range too. 🤷 The Pico TA189 is also interesting, but it's pricey. I don't need a current probe, I want one to screw around with in the range I need.

Thanks,
Josh

slugrustle:
One option for lower currents is looping the wire through the aperture multiple times.  This works if you can afford the extra wire length, extra inductance, and likely impact on bandwidth.

You might find the Aim-TTI I-prober 520 interesting: https://www.aimtti.com/product-category/current-probes/aim-i-prober-520.  The main selling point is the ability to measure PCB traces directly, but it does come with a ferrite clip thing to measure current through wires.  It quotes ±5% accuracy from ±10mA to ±10A in wire mode and has 5MHz bandwidth.  I have one.  The DC offset is manually adjusted with a potentiometer, and it takes some time to stabilize (thermal, I guess). 

The Pintek PA-699 is a little more traditional.  It claims ±3% ±10mA on its 8A range and ±4% ±100mA on its 80A range.  1.5MHz bandwidth.
https://www.pintek.com.tw/productDetail/land-ctop-2/index/pscsn/33672/psn/185730
https://www.globalmediapro.com/dp/A2H116/Pintek-PA-699-Current-Probe-DC-15MHz/

Looks like the same thing as an Elditest CP6990 at a better price.
https://www.caltestelectronics.com/product/CP6990-NA

The Pico TA189 might be better than either of those in terms of price and accuracy if you're ok with the bandwidth.

Another "out there" option is to build your own measurement device based on an isolated hall sensor like a TMCS1126A5A https://www.ti.com/product/TMCS1126.  It's less convenient than a clamp because you'd have to wire it into the circuit under test.  It also outputs 2.5V at zero current input, so opamps (likely with a potentiometer for offset trim) would be needed to convert to proper zero-referenced bipolar levels for a scope input.

If you're keen on the homebrew route, the AMC3301 is another option https://www.ti.com/product/AMC3301.  It's an isolated amplifier meant to interface with a shunt and has an internal isolated DC/DC converter that powers the circuitry on the sensing side. Again, you'd have to wire it into the circuit.  This one has a differential output so it likewise needs some opamps to interface with a scope.

Poroit:
I have used Prova Model 11 extensively and always found it to be reliable.

https://www.prova.com.tw/product_detail.asp?seq=235

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