Bench meter regulation

ocool_15

Member
2004-11-26 3:15 am
sk
I was wondering if it would be useful to make a plug in adapter for multimeters. It just gave me a change battery sign and I measured it at 9.0V and 9.1V on 2 meters and the new battery is 12.8V.
Would that not throw alot of error into measurements? It didnt seem to. I making a big deal out of something the designers already covered? Would a regulated 7812 based supply introduce more noise and thereby throw off accuracy moreso?
 
It would tie you to the power lines, so what you then have is a bench meter.

I never thought battery life was much of a problem with my meters. The internal workings use reference voltages, not the battery voltage itself. Your meter will work as well with batteries 20% low as it will with new ones.

If you power the meter from a wall wart adaptor, then the meter circuit is referenced to that supply. Not a problem maybe with low voltages, but if you measure 240VAC with it or the high voltage of a tube circuit, that means the breakdown voltage between the AC mains side of the adaptor and the low voltage side must be able to withstand that voltage differential.
 

ocool_15

Member
2004-11-26 3:15 am
sk
Enzo said:
It would tie you to the power lines, so what you then have is a bench meter.

If you power the meter from a wall wart adaptor, then the meter circuit is referenced to that supply. Not a problem maybe with low voltages, but if you measure 240VAC with it or the high voltage of a tube circuit, that means the breakdown voltage between the AC mains side of the adaptor and the low voltage side must be able to withstand that voltage differential.


but if its 12V battery or regulated 12V supply it wont make a difference? But your saying it will then? Our lines are 120V here and I've never owned anything with a tube but someday maybe.
I just thought it would increase accuracy if the supply had better regulation.
 
A bettery will have better regulation that the wall wart. That will dance up and down with variations in the powerline voltage.

The meter has its own internal volatge regulation. The meter is designed with batteries in mind. They were aware the batteries would fade over time. The meter will work fine until the battrery goes flat. it warns you when it is low so you can change it before the performance suffers.

Your project might be fun, but it will not improve meter performance at all. My concerns are for convenience and safety. Your idea would work, but as far as I am concerned there is no reason to do it.