EEVblog #296 - AIM-TTi I-Prober 520 Current Probe Review

[mikeselectricstuff]

Interesting ! a search through the UK TTi web-site shows no I-prober 520 being available... looks like they consider UK purchase of this device, not worth marketing in the UK;  or is this a patent distribution, partnership-consortium issue ?... as Dave say's Go Figure. 

http://www.ttid.co.uk/go/iprober/index.htm

I bought mine direct from TTi UK

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[D3f1ant]

So few years on, do people who purchased these things still find them useful and reliable?

[MarkL]

I purchased one before Dave's review and still find it useful.

I've found it most useful to track down shorted components, and once to find an extremely elusive short on a PCB that was poorly manufactured.

The method I use is to inject 1kHz on the shorted signal (typically the power supply) using a small signal transformer, and then use the iProber to track where the 1kHz current is going.  The small tip of the iProber allows you to get down to the exact pin on a 0.1" DIP.  You can easily identify the ingress and egress of the current through the shorted component.

I've also used it to get some rough measurements on in-circuit linear regulator performance without cutting PCB traces.  That's nice.


What I don't like about it:

- Absolute accuracy is poor, even after the calibration procedure.

- It's very noisy on low level signals.  That's why they have a 2Hz BW setting.

- It has an attachment for measuring current in a wire, but I can get better accuracy, much less noise, and much better frequency response with a real AC/DC current probe.

- I really dislike the sensitivity to the earth's magnetic field which can cause large DC offsets when you change the orientation of the iProber even a little bit.  I've been playing with the idea of strapping a 3-axis magnetic sensor to it to generate an opposing offset on the output.

- It would have been nice to provide a USB power option instead of the hassle with an external wall wart.


I've had no reliability issues.

All in all, I still think it was a good purchase.  Just don't believe all the marketing hype that it will fix a rainy day.

[D3f1ant]

Thanks. I need a conventional current probe, and hoped this would fulfil that and be useful for debugging too. Looking at datasheet the absolute accuracy didnt look to fancy, so fear it probably better as a debugging tool than concise  measurements. I'll probably pick one up if it's on promo sometime, but looks like have to spend a few $k on a traditional probe in the meantime.

[splin]

I've found it most useful to track down shorted components, and once to find an extremely elusive short on a PCB that was poorly manufactured.

The method I use is to inject 1kHz on the shorted signal (typically the power supply) using a small signal transformer, and then use the iProber to track where the 1kHz current is going.  The small tip of the iProber allows you to get down to the exact pin on a 0.1" DIP.  You can easily identify the ingress and egress of the current through the shorted component.

If that's your main usage then surely all you need is a tiny coil, and perhaps an amplifier, for tracing an AC signal - for very little money? The question then is can you justify the rest of the cost for the less common use cases?

[D3f1ant]

Exactly. I feel the Iprober is slightly gimmicky. As a proper current probe the accuracy isn't there to justify the price, so I feel it's better to spend 2-3x the money on a proper probe. Now I can't decide if should buy a Hioki and psu or save $ and limit myself to my scope branded ones which are powered direct from the instrument. I have a general distaste for proprietary stuff...but current probes seem to hold value remarkably well.

[MarkL]

I've found it most useful to track down shorted components, and once to find an extremely elusive short on a PCB that was poorly manufactured.

The method I use is to inject 1kHz on the shorted signal (typically the power supply) using a small signal transformer, and then use the iProber to track where the 1kHz current is going.  The small tip of the iProber allows you to get down to the exact pin on a 0.1" DIP.  You can easily identify the ingress and egress of the current through the shorted component.

If that's your main usage then surely all you need is a tiny coil, and perhaps an amplifier, for tracing an AC signal - for very little money? The question then is can you justify the rest of the cost for the less common use cases?

Sure, you could build something that would do similarly.  You could also buy an old HP 547A current tracer probe for less than an iPober.

We had an opportunity to buy an iProber as part of a consulting contract to assist in tracking down failures in a third party, battery-powered energy metering device.  The meter was encountering a number of ESD induced failures.  The major failure mode was CMOS latch-up on various parts, so it wasn't as easy as finding a dead short.

The iProber made it very easy to identify which chips were involved in failures, and down to the pin.  It was a board of about 20 SOICs (0.05" spacing), and a microcontroller with even tighter spacing (I think it was 0.65mm).  That might be difficult to achieve with a home brew coil, especially on a tightly packed board.  And add to that repeatability for the relative value, since it's not an "all or nothing" measurement (there's other legitimate current flowing besides the fault current).

The time saved in not having to build something, and the ease of using the iProber with its long insulated tip was justification enough.  It got the job done.

In the case of the voltage regulator I mentioned, there was a problem with it going into dropout for 50us which was causing a board to reset.  At first it appeared to be the voltage regulator was not up to spec.  It took about a minute with the iProber to figure out it was 1 of about 15 chips that was putting a huge spike on the power rail (it was a bad driver chip).  And without cutting any traces.

The iProber saved me time here too, but of course there's plenty of other ways to figure out this one too.

The iProber is handy to have around, and I use it now that I have it.  Without a specific purpose, my justification would be as a convenience.   It's certainly not a necessity.

[SunnySpring]

I had just got hold of this i-prober. The calibration to PCB trace is too troublesome and requires to know the exact current through the PCB trace (unless this trace is not surrounded by other trace and ground plane).  and you need to adjust the PCB Trace sensitivity [which means you need to know the exact current through the pcb trace anyway.  Then you need to hold the probe vertically and maintain the tip to be perperdically with the trace.  ANd I dont have a different probe to do this PCB trace current measurement with 1 ohm resistor. And then the uncertainty associated with the hand holding the probe.  putting the probe nearby a SMPS inductor coil certainly pick up a lot of field although insignificant with the peak current profile that I am only interested in.

 I wound a 24gauge wire 5 x around the provided wire clamp accessory that is provided with the i-probe and measure current the traditional way with this probe  The trace is very clean and no noise (because I position the clamp away from the board, leaving my hand totally free) and I solved my problem in less than 5 minutes to confirm the intermittent peak current  issue. which exceeded the specs of the SMSP IC momentary.