Tips for Troubleshooting Low Voltage Measurement Issues

Measuring electrical signals at a microvolt level raises the potential for errant readings. Such tiny signals can be easily masked by external factors, including thermal effects and EMI, and internal effects such as crosstalk from other signals on the same board or device. Knowing such obstacles await will give you the opportunity to plan for them and troubleshoot the issues that could arise when taking low voltage measurements.


Sources of signal errors


As consumers continue to look for smaller devices and lighter-weight materials, research and production processes using low voltage measurements are becoming more prolific. As mentioned already, the potential for error in the form of voltage offsets and noisy readings increases right along with the demand for low voltage technology.
While a number of factors can affect the accuracy of your readings, thermal effects represent the largest source of error in low voltage measurements. The key is recognizing the signs of potential errors and adjusting your equipment to increase the accuracy of your measurements.


Voltage offset


Connecting a voltmeter to a test circuit with low impedance should read “zero” if no voltages are present. Thermal effects might be seen as non-zero. Sources of thermal effects include thermoelectric EMFs and offsets coming from the voltmeter’s input circuitry.


Internal Zero offset

Sensitive instruments like nanovoltmeters will very rarely indicate zero when no voltage is applied to the input because there are offset voltages that can’t be avoided in the circuitry. The first step toward troubleshooting this offset begins with checking the instrument’s zero offset after allowing it to warm up. After disconnecting it from the external measurement circuit, select the desired measurement range and then short the test leads together.

This is only a very brief introduction into the troubleshooting process for low voltage measurement issues. If you’re working with a particular measurement device for the first time, it’s always a good idea to seek out help from the experts, and MATsolutions is here to help. Contact us with your questions regarding low voltage measurement, or visit our website to learn more about our test and measurement products.


Image: Effects of offset voltages on voltage measurement accuracy. (Keithley)