Interesting Current Probe

Yes I saw that, but still a lot cheaper than my Tek P6021 (overkill admittedly as most of my applications are in the 1kHz-1.5MHz range) and of course the Iprober does DC too. I will see if I can get a demo.

JB

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It's obvious it won't take calibrated readings and that it will be sensitive to position and whatever external fields are there.

"Nevertheless, the use of the I-prober 520 requires interpretation based upon a proper understanding of circuits and systems. It is a tool for the professional engineer and is not suitable for use by just anyone."

If there's such a disclaimer and it's not in fine print, that should tell you something.

Not saying it's useless, but it's not some sort of magic wand you can wave around at random and get consistent, useful readings. Especially for newbs.

Well, that disclaimer goes for about any measurement you make :-) I recently had a problem with a switcher design so I really needed to measure the currents. Preferably primary and secondary. I used 2 SMD current sensing transformers to make 2 current probes. Works like a charm.

Whew. I paid $175 for my P6042.

Cheers

Phil HObbs

Yes I got this too and am thinking of getting one.

It looks like the "sniffer probe" idea described in Appendix E of this Jim Williams app note (AN118):

There look to be enough details to make your own or you could buy it.

This new one claims a new type of sensor IIRC, could be a useful addition to the collection. But it not clear if it has any advantages over a home made one.

Not as accurate as a proper current probe and more expensive than some second hand ones. But the whole point is that you can probe around PCB tracks without having to break the circuit.

That one is not going all the way down to DC. Which is rarely needed anyhow. But I found that probes being sideways at the end are better, they couple much more tigghtly to the trace. So that's what I am using in my noise hunts. I have an EMCO near field kit.

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Gah! I HATE shiny brochures.

It alleges new sensor technology.

Screw the babble, what physics principle is it based on? I couldn't force myself to read the damn thing.

Mark L. Fergerson

Yes good point, forgot about that. Hall sensor?

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It's a fluxgate that has been miniaturized into their tip (so, the probe is possibly a delicate and expensive part to drop on the floor). The sublink on the page that explains this, is=20

It's uncertain what the high frequency applicability is, because they have a local oscillator that can beat against the input signals, but it should be a stellar performer at low frequencies (and will age much better than Hall sensors would).

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What is the aging mechanism in Hall sensors? How would it show up in the readings?

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Does it still work?

It works perfectly. eBay is a wonderful thing, if you're patient.

Cheers

Phil Hobbs

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The Hall effect is small, so it might only generate a few microvolts; it takes lots of amplification. Any noise, including popcorn noise and=20 the kinds of leakages that cause amplifier drift, will matter. Some=20 inexpensive Hall sensors are so sensitive, that strain on their leadwires has a non-negligible effect - the better sensors have a ceramic substrate.

Several years ago I asked here if scrap hard drive heads could be used to make a current probe (of some limited bandwidth). If you only need AC measurement I still wonder if a poor man's version is feasible.

(Cross-posting to csiphs where people have an interest in HDD heads.)

I doubt it. The problem is that any reasonable current probe needs to wrap a core around the wire being probed and then reads the current on a second winding. That is the reason for the "clamp" design. The "clamp" is actually a ferrite core. If you do not do it that way, you get extreme influence from distance, 1/(d^2) for a straight wire.

Also, HDD heads are both extremely fragile and used for high field strengts at high frequencies. I do not see them ever working reasonably as current probe, even if you glue them to the wiore being probed. The amount of advanced DSP needed to make sense from their output is just not worth it.

Arno

The probe in discussion (link quoted above) has all the same drawbacks (except bandwidth limitation) but costs $800. I thought a head might provide the assembly for a poor man's version.

A head is essentially like the probe in Appendix E here:

But I guess a head might be designed for a very narrow band.

Also, it might be used for finding sources of EMI rather than precise current measurement.

Modern hard disk heads are _quick_. They take some care, though--they aren't inductive anymore, they're magnetoresistive.

Cheers

Phil Hobbs