A typical 3 ½ or 4 ½ multi meter can measure voltage in the low mV range and current in the low mA range. Voltage measurement in the µV range and current measurement in the nA range are typically only available in the more expensive lab bench multi meters. In this post, I will show you a simple adapter circuit that can be used for precision voltage measurement down to the µV range. Using this circuit along with the current adapter circuit I discussed earlier you will be able to perform most of the low level measurements with a 3 ½ meter.
This circuit is built around TI’s programmable precision instrumentation amplifier LMP8358. The basic circuit is quite simple and is shown below:
The gain is determined by the DIP switches and the Op-Amp LM358 forms a virtual ground circuit so that voltages of both polarities can be handled. Using both supply rails also has some additional benefits. Because either positive or negative signals can be measured, this circuit is capable of measuring AC voltages with a frequency up to 80kHz at the gain of 1000 or 8MHz with a gain of 10.
Read More: Precision Voltage Adapter For Low Voltage Measurement