Review of the digital multimeter (Fluke 87) shows a discussion about making current measurements with the usual how to instructions. Near the end of that section, voltage burden is introduced. The “mA” range has about 1.8-ohms resistance, so as the current increases the voltage drop across the meter resistance starts to have an influence. If the source voltage is relatively low the voltage drop has a profound effect.
A short study using a 6Vdc source with various load resistance showed that the error at 400mA was greater than 10% and with burden compensation calculated the error was less than 1%.
Bottom line – you should become very aware of the voltage burden and compensation that may be required for any measurement. The “A” range has a voltage burden too because of 0.03-ohm resistance, so certain conditions could have an effect.
For more information about voltage burden effects – contact us.Article Reference ID: DYK00008
Posted in: Did You Know? Measurements