[pre_ad postid=”7650″]By Joe Glassford. Accuracy of: Plus or minus 0.1% is Best. Check the owner’s manual for your meter under DC accuracy.
Lets compare meter readings of Best (0.1% accuracy) to Poor (1% accuracy). If the actual charging voltage was 14.30V
and your meter had: Plus or minus 0.1% Accuracy (Best) This meter could read: @ + .1% —– 14.31V @ – .1% —– 14.29V and be off actual by .014V.
and another meter had: Plus or minus 1% Accuracy (Poor) This meter could read: @ + 1% —– 14.44V @ – 1% —– 14.15V and be off actual by .143V.
If the actual battery open circuit voltage was 12.66
and your meter had: + / – 0.1% Accuracy (Best) This meter could read: @ + .1% —– 12.67V @ – .1% —– 12.65V and be off actual by .013V (13mV).
and another meter had: + / – 1% Accuracy (Poor) This meter could read: @ + 1% —– 12.78V @ – 1% —– 12.53V and be off actual by .126V (126mV).
Less than .050V (50mV) is a common acceptable voltage drop on a sensor or computer ground. If your meter is off by .126V (126mV), as illustrated in the example, you will never find the problem.
A Word About the .5% Accurate Meter
Some instructors and training facilities claim that for testing on vehicles using modern computers and electronic control modules a meter with an accuracy in the DC Voltage range of .5% is acceptable. I wish to take exception to this claim. Take a look at the statements below:
Using a .5% accurate meter, if the actual voltage is 14.30, your meter could be off in the + .5% side and it would read 14.371.
It could be off in the (-) .5% side and it would read 14.228 the .5% accurate meter can be off the actual reading in either the high or low percentage by: .071V or 71mV.
However, when testing on the ground side of control module or sensor, you are looking for a maximum value of 50mV (.050V) A .5% accurate meter would only be off by .000250V or 250μV that’s 250/000,000 of a volt. The .5% accurate meter would be accurate enough for this testing.
My suggestion then is if you want to be ready for the 21st century in vehicle electrical/electronic diagnosis, and you are now in the market for a new meter, buy a .1% accurate meter or better.
