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Registered Member #1316
Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365
I was thinking of buying a current probe (tek p6022) for general electrics use. I think it would be useful for calibrating CT's and calculating transistor loss by finding the V*I overlap. It would also be useful for some class E amplifier work. I am probably going to drop around $250 on the probe.
I just wanted to get the general consensus from the people on 4hv on the usefulness of a current probe before I buy one.
Also, I have one question about the current probes. I know they are for only measuring the AC component of the current. However, how do they preform with unipolar pulses? The max DC component the probe can handle without saturating is 0.5 amps. For a unipolar pulse train would it saturate when the RMS current is 0.5 amp? Would it give accurate current measurements up to that point?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I use a current probe almost every week, some (the cheaper ones) are just current-transformers and are ac only some (more expensive) are hall-effect ac/dc probes more than 90% of the time an ac probe is ok though some problems do require a dc probe.
I suggest that you wind 1000 turns on a high permeability MnZn toroid core as a current transformer, (100 turns on a NiZn for hf to vhf) then use a 'burden' resistor for the range that you want (e.g. 100 Ohms 1 watt = 100 mV per amp, 100 amp max. etc.) .. more accurate than a commercial probe (no leakage or stray pickup) but you loose the convenience of 'clamping' .. not a great loss for hobby work. If 'clamping' is important to you then use a 'U' core for the winding and an 'I' or 'U' core to close the magnetic path.
i.e. I would use a ct to calibrate a current probe .. not the other way around.
Use your hobby $$ for either a hv or differential probe - depending on your interests.
Registered Member #1316
Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365
I already have a P6015 1000x hv probe, they are easy to get. Differential ones still cost more then my scope. The current probe would mostly for class E amplifier work for my next years science fair project. The clamp on it is even small enough to fit on larger component leads mounted to the PCB.
How would a home made current transformer be more accurate then a current probe? The current probes have relatively flat response from only a few Khz to the Mhz range. I have heard people having issues with the phase shift of home made current transformers at frequencies lower then that.
Registered Member #989
Joined: Sat Sept 08 2007, 02:15AM
Location: São Paulo, Brazil
Posts: 476
I done a current probe myself, buying a cheap oscilloscope probe at Dealextreme and soldering the current transformer and burnden resistor to it. I have a few pics. It is a 1:100 Transformer with a 10R Burden resistor. in the 1x of the probe, I get 1V per 10A, or in 10x I get 1V per Amp. I made it to measure the current of DRSSTC primary:
And here a pic of the primary waveform, measured with that probe (The Yellow one)
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Usefullness Of Current Probes
