Need a small current probe to suit usage with multimeter

[Tubetec]

Ive been looking around for a small low current clamp to use along with my multimeter for measuring mA .
The best I could find at a reasonable price is the Chauvin Arnoux Mini 5 .
It has both 1:1 and 10:1 modes . It says its measurement range is only good above 5ma which isnt great for say checking the cathode current on low powered tube gear .
There are of course current leakage testers , fluke do some nice ones ,but they cost big money , there are a few other budget leakage meters , but the clamp itself tends to be huge and not suitable for small stuff .

Some current clamps are crazy money , the smaller high quality ones tend to cost even more . Any advice appreciated .

 

[shabtek]

I'd imagine affordable clamp on in not very sensitive. i have only used them to measure ac Amps

what about measure voltage drop across 10Ω? and move the decimal over.

 

[ccaudle]

Assuming you are talking about small AC currents, I think the problem is that small current implies small magnetic field. To get a reasonable voltage from a small magnetic field, you basically have to build a high ratio step-up transformer, which means a pretty big coil of wire.

How small are you talking about? That Chauvin probe says 1mV/mA, so a couple of mA AC current would generate a couple of mV. Small voltage.
What about building a small amplifier circuit to go between the probe and the multimeter? A gain of 100 would get into range of any decent multimeter.

 

[Tubetec]

Some of the add on current clamps have active circuitry and a battery but they still tend to be of lower sensitivity .
I have a good multimeter capable of measuring sub milliamp currents .
The jaws of the clamp form one primary turn , I guess it wouldnt be too difficult to add extra secondary turns to increase the sensitivity even on a passive system . The other thing I was thinking of wiring up the usual clamp in balanced fashion to a mic pre and applying a set amount of gain . The passive clamps tend to have quite low bandwidth , usually upto around 500hz . I know its a simple matter to determine current via voltage drop across a known resistance , but say measuring the cathode current of a power tube with its cathode connected to ground , be quite handy not to have to splice in a 1 ohm resistor and be able to take a direct measurement .
Thanks Shab and CC .

 

[Tubetec]

I missed a Fluke 772 current clamp meter going cheap on a local website , basic sensitivity is uA ,serious bit of kit .

 

[Audio1Man]

Hi All
Make a CURRENT AMPLIFIER (Field amplifier). Just make two or three turns through the pickup and the probe 2x or 3x times the min sensitivity.

Duke