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Precision voltage source – voltage calibrator

Posted on Thursday, August 31st, 2017 in DIY by DP

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Mare writes, “What I missed in my workshop is nifty small programmable precision voltage source which can be used as calibration voltage source for testing and calibration purposes. I decided to make one, because instruments which have word “calibrator” have price with same digits as there is vocals in this magic word.”

More details at Mare & Gal Electronics.

This entry was posted on Thursday, August 31st, 2017 at 4:06 am and is filed under DIY. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

3 Responses to “Precision voltage source – voltage calibrator”

  1. Drone says:

    From the block diagram and the designer’s Blog post on this supposed Work-in-progress, to me it looks like there sooo many things wrong – right from the start!

    Once you have a “Requirement Specification” of what the “Reference” is supposed to be capable of, the next step is to do both Accuracy and Resolution “Budgets”, as well as how the two interact. Once a design block diagram starts to settle out, next comes the (usually difficult) analysis of stability.

    The designer skips ALL of these steps and seems to simply launch into system design. IMHO this is a recipe for FAILURE.

    You can’t design a “Reference” without some way to test it against calibrated standards. This involves a LOT of necessary equipment, not only calibrated metrology, but thermal environment chambers as well.

    Obviously, launching into designing a “Reference” because you don’t already have a “Reference” is pure nonsense.

    Finally, the designer’s approach seems to lean heavily on ADC/DAC stages. While this is seemingly a panacea (to the uninformed), it really isn’t. Multple ADC/DAC stages in the design introduces a LARGE number of degrees of uncertainty.

    There are plenty of excellent monolithic fixed voltage reference parts already out there, and they are available at multple voltages. If you really want to your reference to be “programmable”, take a look at the YouTube video tear-downs of some venerable manually switched wide range analog reference sources available on the Daves EEVBlog – as a start.

  2. KH says:

    Agree, I don’t think anyone should rely on this design for serious work without carefully studying the main circuits. But well, nobody in a commercial setting should be using DIY equipment like this unless they really, really know their stuff. I made a dual low-voltage fixed ref board myself to check cheap DMMs: ADR3412 1.200V 1% and ADR431 2.500V 0.04%, and I have seen the eye-watering pricing for some of these parts, so I wonder what he really means by +10.000V, heh heh.

    I am mostly interested in his parts selections for the +10.000V reference, DAC and main opamp, but the schematics in the PDF seems to be mostly the switching power supplies and the battery/charging stuff. Also how he’s getting the voltage value for the display. And the load capability for the amp, since if it has large current capability, the device and surrounding parts dropping all those volts and amps need to be pretty temperature-stable for stable and accurate output.

    • Drone says:

      @KH, a I agree with what you’ve said. I posted a comment on the designer’s page about this project that points back here. I suggested he/she read the comments here for some added insight.

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