Annoyed with unstable voltage sources in your projects? EDN shows how to build a precision voltage reference and an output buffer for a high precision voltage source/sink. Grab the schematic off of EDN’s site.
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Annoyed with unstable voltage sources in your projects? EDN shows how to build a precision voltage reference and an output buffer for a high precision voltage source/sink. Grab the schematic off of EDN’s site.
Ok…, now I want one of those neat 5 decade Kelvin–Varley dividers… Or I just have to fork out $850 for a 7 decade Fluke 720 at eBay.
Nah, for $800 I can get a crappy Chinese laser cutter instead – that would be more fun I think. :-)
.. until the tube burns out.
Can anyone tell my why you can’t just use a high precision DAC for a precision voltage source?
You probably could. If you are using a >=17 bits DAC, a proper reference voltage, battery power and the buffered the output of the DAC. You probably have to get up to 20 bits to achieve the desired Linearity and monotonicity for the required 17 bits for a 5-decade unit.
The Kelvin-Varley unit could also double as a resistor decade box as well as doing the voltage sink/sourcing if you add a switch for it though…
I have the 5.0000V ref from http://www.voltagestandard.com/ and it is very easy to use
The Voltagestandard products seems to have reasonable prices. The DMMCheck Plus for $59 is almost a steal.
But I get a bit of “Digit envy” when I see their 8.5 digit HP3458A, my main DMM is only a 6.5 digit Agilent 34401A currently two years out of its calibration date. :-)
Check out Geller Labs for an excellent value 10.0000 V reference.
…specifically, they sell the “SVR” which is a 10 V, NIST-traceable 10 ppm accuracy reference for $40 which is the best deal I’ve seen. You do need an external +15V supply to power it. http://www.gellerlabs.com/Voltage%20References.htm