How can I calibrate a multimeter with "domestic stuff"

[Nickhlx]

Well perhaps a bit more than "domestic stuff" - I have quite a variety of electronic components including resistors, diodes and zener diodes and a nearby Maplin in case a particular component would be needed / useful.

 

I have 3 or 4 multimeters, mostly cheap but one is an old Maplin Gold which I think was "better than average", but being old has probably lost any calibration it may have had...

 

Basically what I am wanting to check / adjust is the DC 0-20 volts range to as accurate as possible. I know I need to try to generate some sort of known reference voltage somehow at around ideally 19.9 volts but perhaps around 12 to 15 volts would be adequate ? Perhaps I can calibrate/adjust the 0-2 volts range and pot down 0-20 volts with high accuracy resistors and measure 14 volts via this external potential divider and measure on this range ? With two or more meters, perhaps they can be used as an interim measuring device to set my better one ?

 

So can anyone suggest any methods or even a circuit I can knock up to provide some sort of reference ?

 

Suggestions welcomed

 

Thanks,

 

Nick

[Keeping Up]

Can you borrow (or even hire) a decently accurate meter for an afternoon? That has to be the easiest way.

[Nickhlx]

Can you borrow (or even hire) a decently accurate meter for an afternoon? That has to be the easiest way.

 

 

Yes - I possibly can, come to think about it - I know a (techie) guy who works for Motorola and he would probably be able to borrow a meter overnight ... probably the "sensible solution"

 

( but I don't want to do that if I can make / have my own calibrator I would like to "have a go" )

 

Nick

[Keeping Up]

If you could borrow the use of meter, you could make a calibrated sub-standard that you could use for the future to check your own

[Gibbo]

There are 2 very simple options.

 

1. Borrow a known good meter and use anything you can find that gives a voltage roughly in the middle of the range. A boat battery, a PP3 battery etc will do. Put both meters on the voltage source and calibrate one against the other.

 

2. Google LM4040. This is a precision voltage regulator available in different voltages. One of those, a series resistor and a small capacitor, all on a battery, will give you a rock steady voltage reference within 0.1% to calibrate your meter against.

 

I think the LM4040 is probably about 50 pence retail.

 

Forget zeners. They're nowhere near accurate enough.

 

Gibbo

Edited May 4, 2008 by Gibbo

[Nickhlx]

Thanks guys,

 

I'll get the LM4040 / calibrate a substandard and then I'll be able to tweek all my meters to greater accuracy

 

Cheers,

 

Nick