I am building a system for a bike where a dynamo charged a li-ion cell which can be used to charge USB lights or mobile phones etc. I have a small digital led panel volt meter measuring the battery voltage. My problem is that the meter always reads 0.05v higher than the actual reading. Is there any known way to calibrate these cheap meters? Cheers

 

I think accuracy within 0.05V is pretty good and better than a lot of digital multimeters.

 

My problem is that the meter always reads 0.05v higher than the actual reading.

1% is very good. How do you know that the DPM is wrong? Why do you care? Most devices will tolerate at least a 10% supply variation. The USB spec allows +/-10%.

Is there any known way to calibrate these cheap meters?

Part number? But not likely unless it's an expensive one.

 

Most of the little cheap panel mount volt meters I have, have a tiny little pot on the back to adjust the meter.

 

I am building a system for a bike where a dynamo charged a li-ion cell which can be used to charge USB lights or mobile phones etc. I have a small digital led panel volt meter measuring the battery voltage. My problem is that the meter always reads 0.05v higher than the actual reading. Is there any known way to calibrate these cheap meters? Cheers

Some small DPMs (Digital Panel Meters) allow for calibration and some do not. Some use a small potentiometer and some you go through a programming routine. This all depends on the meter and manufacturer. If you can find a manual or data sheet for the meter it should tell you if it can be calibrated and how to go about it.

Additionally an error of 0.05 volt is awfully small. At 12 Volts an error of 0.05 volt is less than a 0.5% error which isn't all that bad. Now if you want better uncertainty, like ±0.02% of reading ±1 count on a 4 1/2 digit display 20 volt range and 1.0 mV resolution, you can have that but will pay for it. Meters like this also allow scaling and calibration as long as you have the standards needed to calibrate it.

Ron