Building a voltage reference

[TarHeelTom]

build circuit voltage reference

I would like to build a stable, stand-alone voltage reference, with the output somewhere in the 13 to 15 volt range.

This will be used to check the calibration of VOM's or DMM's. The idea here is to be able to take a (cheap?) DMM and measure the voltage of a battery in a vehicle under various load and charging conditions and KNOW fairly accurately how far off the measurements are from the actual measurements.

This assumes that the error in the DMM, in that range, will be linear. (Will it be?)

Basic idea is probably a pair of nine volt batteries in series, a switch, a resistor, some sort of very stable voltage regulator, then a couple more resistors leading to a pair of external 5-way binding posts. The whole shebang would then fit in an Altoids can.

I can build something that works, but have no idea what regulator to use to make it stable. I'd like to take it somewhere once every year or two and verify the calibration, but not have to worry about it in the interim.

Anyone have any ideas?

Thanks

Tom

 

[millwood]

build voltage reference

a 13-15 precision voltage reference is hard to find, and difficult to build.

however, there are plenty of 1-2.5v voltage references. you can use them to caliberate your DMM and then use a resistive divider in front of the DMM to measure the battery.

the simplest would be a tl431 type voltage reference. if you need a wide operating voltage range, look into a bandgap reference.