Author Topic: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???  (Read 3627 times)

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JuanPC

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Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« on: July 24, 2013, 04:14:03 am »
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Offline c4757p

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #1 on: July 24, 2013, 04:17:06 am »
There are a lot of things under the umbrella of "30A current probe". DC or AC? What are you looking to do with it?
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JuanPC

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #2 on: July 24, 2013, 04:25:52 am »

To Measure Inrush Current of an AC Power Source, DC current could also be interesting.

How much Amps does a "standard" probe can Measure?
« Last Edit: July 24, 2013, 04:32:42 am by JuanPC »
 

Offline David_AVD

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #3 on: July 24, 2013, 04:57:01 am »
Maybe post a link to an example of what you're referring to and how much it is vs how much you want it to be?
 

Offline AlfBaz

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #4 on: July 24, 2013, 05:41:17 am »
CT's are cheap, get a suitable one usually available in xxxA:5A or XXXA:1A, plug it into a decent multimeter with peak record function and away you go
 

Online notsob

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #5 on: July 24, 2013, 07:09:01 am »
Depends on what your requirements are, if it's just an indication without having to do much else, try an induction ammeter, otherwise a clamp meter.

http://www.hoytmeter.com/products/test-equipment/induction-ammeters
 

JuanPC

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Offline Rerouter

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #7 on: July 24, 2013, 08:07:28 am »
its to accurately measure current at 50Mhz for one of the example, that requires quite a bit of guru level magnetism magic to pull off,
 

Offline KedasProbe

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #8 on: July 24, 2013, 09:27:13 am »
50MHz & 30A   ?? ??
Not everything that counts can be measured. Not everything that can be measured counts.
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Offline Neilm

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #9 on: July 24, 2013, 06:07:53 pm »
50MHz & 30A   ?? ??

You would need that sort of bandwidth if you wanted to measure the primary currents in DC-DC switch mode power supplies.

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alm

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #10 on: July 24, 2013, 06:19:11 pm »
If you want useful answers, than please provide some details. Your posts have been absolutely useless so far. You specify that it needs to measure 30 A (RMS? peak?) AC. Are we talking 60 Hz or 50 MHz? What does a Tek 1 GHz differential probe have to do with this? You also don't explain what expensive is. Are you a hobbyist trying to get one for $10? Is this for business with a low budget?

I would either look at current transformers (for low bandwidth), or I might hit eBay for used probes. The Tek P6021 (note that you need the termination or an active amplifier) tends to be quite affordable ($100 or so), but will only do ~10A RMS. The Tek CT-4 is a current transformer that will extend the current range of a probe like the P6021, but only has 20 MHz bandwidth.

Don't be surprised to pay over $1k new (I think a new Tek P6021 might be in that ballpark). These are not mass market items, and manufacturing the ferrite is a fairly complicated process. Now it becomes even more fun if you want to include DC. I believe there are three companies in the world (Tek, Lem and Hioki?) that make current probes from DC to the MHz range, and none of them is very affordable. They're also very fragile and expensive even on the used market.

In the high end it's not unusual to pay as much if not more for the probe than for the scope.
 

Offline nctnico

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #11 on: July 24, 2013, 07:17:50 pm »
Wait a little bit... I'm working on an affordable current probe as a product because I keep running into the same problem. My probe won't be a clamp so the circuit needs to be opened. Preliminary specs: dual channel DC to 10MHz / 10A RMS. 30A peak shouldn't be a problem. Both channels are isolated. The PCB for the prototype is being made...
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Offline Spunky

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Re: Why 30A Current Probes so $$$$$$$$$$$$$$$$$$$$ ???
« Reply #12 on: July 25, 2013, 02:22:37 am »
Just buy a clamp meter with inrush current measurement

If you want to do it with probes, you don't need 30A rating anyway as the inrush only lasts a couple of cycles. That's why you can run a vacuum cleaner with 30A inrush on 1mm flex, it's too quick to even trip a breaker.

Also why not measure it the inrush voltage (rather than current), then do it again at the end of a long extension lead and compare against a known resistive load (fan heater perhaps), then work out the cable impedance from the known load based on voltage drop, and work it backwards again for the test item to find it's inrush current.
 


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