New 200A / 2000A current probe / clamp

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New 200A / 2000A current probe / clamp

Postby Alan » Fri Aug 09, 2013 11:36 am

Hi,

We have just introduced a new 200/2000 A current probe (for some reason many in the USA call these current probes, whilst in the UK and elsewhere they are more often known as current clamps, both terms mean the same).

We have been asked a few times how the new clamp compares to the other clamps we offer. Firstly in terms of size, this photo shows the range with from left to right - "Old" 2000 A clamp, "New" 200/2000 A clamp, 600 A clamp and 20/60 A clamp. As you can see the new clamp is similar in size to the existing 600 A clamp. The jaws are big enough to get around any battery cable I have come across - to be honest the old 2000 A clamp is a bit of a monster size wise compared.

pico current clamps.JPG


Of course all of you read the instructions carefully :wink: but there are a couple of things to note when using this clamp:
1. The clamp performs an auto-zero when you switch it on so switch it on BEFORE you put it around a wire.
2. It features an auto power off after about 10 mins so if you forget to switch it off it saves the battery. There are of course times when you need to measure for longer periods (eg vehicle shut down / ECU shut down testing). To disable the auto power off simply hold the auto zero button when you switch on the clamp. If auto power off is enabled the LED will be green, if it is disabled then the LED is red. If the LED flashes (either red or green) its time for a new battery.

High Current Measurement

For this first test I compared the old 2000 A clamp, the new clamp in 2000 A mode and the 600 A clamp whilst starting a diesel Volvo XC90. This vehicle normally pulls above 800 A when starting from cold, but this was done with a warm engine on a warm day.

starting test current clamps.jpg


All three clamps performed equally well. The main conclusion here is that I prefer the new clamp to the old 2000 A clamp on size alone. Whilst not needed here the higher range over the 600 A clamp will prove useful when working on commercial vehicles and high compression passenger vehicles where the starting current can often be 1000 A.

Low Current Measurement

So how does the new clamp work with lower currents - can it work as well as the 600 A clamp? Whilst still connected to the battery I switched the interior lights on and off. This caused a jump of about 1 A. The top trace is the new clamp set to its 200 A range and the bottom is the 600 A clamp. I did not include the old 2000 A clamp here as it was too noisy to spot the 1 A jump.

oscilloscope current probe waveform.jpg


It's clear that the new clamp works much better on this 1 A test compared to the 600 A clamp. OK by enabling the filter option in PicoScope we could have cleaned the trace up a bit, but the point here is that the new clamp can not only measure much higher currents than the 600 A clamp, it can also measure much lower currents as well.

Clearly the new 200/2000 A clamp is an improved alternative for both the existing 600 A and 2000 A "high amps" probe.

Even lower currents

Given that the new clamp is better at low current measurements than the 600 A clamp the obvious question is can it also replace the "low amp" 20/60 A clamp. The waveform below shows a 500 mA switching signal captured with both clamps. The top trace is the 200/2000 A clamp and the bottom is the 20/60 A.

200A vs 60A modes.jpg


Clearly we are now beginning to see the limitations of the new clamp. I am however very impressed as a single clamp can measure up to 2000 A yet still resolve signals well below 1 A. It does not replace the need for a "low amps" probe but can certainly be used for many measurements such as injectors, fuel pumps etc. Out of choice I would have this new clamp and the 20/60 A clamp in my kit. I can see times where I would use one for say injector current and the other for primary ignition current.

I would say you can use it for signals down to about 100 mA, perhaps a bit lower with filtering - say 50 mA. That will also allow it to be used for those dreaded battery drain issues on vehicles where the jaws of the 20/60 A are that little bit too small to get around the battery cable. OK for this test you ideally want to be able to resolve down to say 10 mA to test to the manufacturers spec for quiescent current, but in reality if you can be sure the vehicle is drawing less than 50 mA then you can eliminate this as the cause of a battery going flat. An 80 Ah battery with a 50 mA drain will last for weeks before going flat.

More info on the clamp including the all important price can be found here:
https://www.picoauto.com/current-probe.html

Update : One of my colleagues has pointed out another key advantage of the new probe I forgot to mention here. The "old" 2000A amp clamp and the 600A clamp have 400Hz bandwidths so are fine for slowly changing signals such as starter motor currents etc. They are not suitable for faster signals such as injector currents. The new 2000A clamp has a 20kHz bandwidth (which is the same as the 20A/60A clamp) so is fast enough for injector / igntion signals etc.
Alan
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Re: New 200A / 2000A current probe / clamp

Postby Robski » Sat Aug 10, 2013 9:53 pm

When (if at all) do you plan on doing a micro amps clamp/probe ?
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Re: New 200A / 2000A current probe / clamp

Postby Alan » Tue Aug 13, 2013 12:00 pm

Hi Robski,

Good question. The 20/60A "low amps" probe can detect changes down to say 25mA so is OK for nearly all low current measurement.

The obvious exceptions to this are

A) Magneto resistive ABS sensors which tend to switch from about 5 to 15mA. Most of these can also be seen as a voltage change - the voltage is often near battery voltage, but AC couple and you can usually see the signal switching. When this does not work then often you can loop the wire through the jaws of the current clamp 2 or more times. Looping a wire through the jaws 2 turns doubles the sensitivity of a current clamp by 2 times. Three turns by three times and so on.

B) Some wideband lambda / O2 sensors. Some of these switch from about -1mA to +1mA. Again some can be seen via voltage changes but for those than can not the 20/60A clamp is going to struggle.

One option is as above - loop wire through the jaws multiple times. You will need to do this probably with 50 turns however so its unlikely you will have enough slack wire. Some people get around this by making up a 50 or 100 turn coil of thin tinned wire - whilst this works, you do have to break into the sensor circuit to insert the coil of wire in series.

We can make a clamp to do this, but it will be perhaps 2 or 3x the price of the existing clamps. Unless there are other uses where the 20/60A clamp can not do the job I am not convinced there will be enough demand?
Alan
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Re: New 200A / 2000A current probe / clamp

Postby Robski » Tue Aug 13, 2013 2:51 pm

We can make a clamp to do this, but it will be perhaps 2 or 3x the price of the existing clamps. Unless there are other uses where the 20/60A clamp can not do the job I am not convinced there will be enough demand?

Yes there is that, baring in mind the cost of a Chauvin Arnoux :roll:

I'm aware of the looping round the jaws trick & TBH i don't really want to break into the wiring, it's possible with the breakout leads but a bit of a faff, so much easier sticking a clamp on !
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Re: New 200A / 2000A current probe / clamp

Postby eric989 » Thu Aug 15, 2013 8:25 am

Hi Alan,

Will you stop selling the old 2000A and 600A current clamps in future, because of the excellent new clamp coming out?

Cheers,
Eric
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