Electronics > Projects, Designs, and Technical Stuff
Linear Power Supply based on HP/Agilent E3610A
timsu:
Should the ADC/DAC should be level shifted up to get a higher accuracy at lower output voltages and allow better calibration?
Kleinstein:
It depends on the quality of the ADC / DAC whether it might be worth using different ranges.
As the modern sigma delta ADCs offer rather good resolution, there is usually not need for a range switching. Also many ADCs measure negative values as well, so no problem with offsets around zero. It might be a good idea to make use of the differential inputs.
For the DAC it might be worth using two ranges, as really good DACs are expensive. A little shifting near zero might be needed if digital offset calibration is wanted.
timsu:
How would be the differential inputs used?
What would be connected to the inverting inputs other than GND?
Kleinstein:
The GND for current sensing (e.g. pin of shunt -> amplifier for current reading) can be a little different from the Ground for voltage sensing (e.g. Sensing line to output connector). For a low ohms shunt the wires/lines going to the resistor can add to the resistance. So voltage should be read close to the resistor, possibly even using a shunt with 4 wires. The difference will not be large, maybe a few mOhms times the output current, but it's possible with little effort to avoid the error.
mcckevin:
Hey Roberoni --
I just stumbled across an E3610 with the same problem. I also replaced U4 (great minds ...) with little success. Did you have any luck with this? Thanks.
Kevin
--- Quote from: Robaroni on June 01, 2016, 12:46:20 pm ---I have an E3610A that the current adjust seems to drift. That is, I can't set the current to zero. I tried to recalibrate the supply but after awhile it drifts above zero and can no longer be set to zero.
I swapped out the current opamp U4 as I didn't see anything that stuck out as being bad but it didn't fix the trouble. It might be something as simple as the wire wound current pot breaking down but I was wondering if any of have seen this problem before I dig it apart.
Thanks for the help,
Rob
--- End quote ---
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