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Stable AC current source for "calibration"?

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c4757p:
So, I finally got my Fluke 45 fixed, after multiple broken parts. One of the parts that I had to replace was the EEPROM, which was totally dead, so I'm in the process of recalibrating it. So far I've managed to calibrate everything except the AC A range, because I can't think of anything stable enough to use as a standard. If anybody is curious, I've found these to be quite stable enough for the other modes, and used my HP 3468A to measure them as a transfer standard.


* DC V less than 20: Power Designs 2005 precision power supply
* DC V less than 50: Power Designs TP343A (seriously, this is actually stable enough that even the least significant digit on the 3468A completely froze)
* DC V 50-1000: homemade boost converter
* DC mA/A: homemade constant current source
* Ohms: Resistors mated to heating elements for thermal stability
* AC V less than 7: HP 3325A
* AC V greater than 7: HP 3325A -> buffer -> transformer
* Frequency: HP 3325A locked to a rubidium reference
I have no idea how to get a stable AC current source. For the lower current ranges, I suppose I could feed a constant AC voltage through a resistor, and just measure the current sense resistors in both meters and mathematically compensate for the difference. I don't really like that approach, though, and I like it even less for high current because of the heat generated. Any ideas? (And does the waveform matter? I would assume it should be a sinusoid, but a square wave would be much easier.)

oscopeface:
I'm not sure if any of that equipment will really get you true calibration? I calibrate those Fluke 45's all the time using a Datron 4808 or Fluke 5500 Calibrator at work.
I don't think a homemade AC current source will do much for you in terms of a real calibration.

c4757p:
Well, as I said I'm using my 3468A as a transfer standard, and I'm OK with that. I don't need the value to be exactly what I want it to be, I just need it to stay fixed between measuring it on the 3468A and typing the measured value into the 45.

mzzj:
I would use same strategy  as with AC volts:  HP 3325A -> buffer -> transformer

Just reverse the transformer to get higher amp low voltage output. Add some series resistance to help keeping the current stable.

I don't think it would be that difficult to keep it enough stable.  Besides, You need something like stability only for 1 minute to write down numbers from both meters. 

Another option would be true voltage controlled bipolar current source, but I don't think its really necessary.

AlfBaz:
This may take a bit of looking into but you could use a transformer. You pass the current through the primary winding (so that is in series with the load) and then run some dc current throught the secondary. by varying the DC current in the sondary you are basically saturating the core thereby creating a "variable" choke

If I remember correctly the more you saturate the core the higher the reactance in the ac winding, so if the AC current increases you divert some of it into the scondary via a rectifier, increasing the reactance. If the AC current starts to drop the dc current in the secondary drops lowering the reactance.

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