The 30-Volt Voltage Probe (30V-BTA) probe was designed to monitor alternative energy sources like large solar panels or wind turbines. The unit has a 30K ohm input impedance. This is low enough compared to the the usual input impedance of multimeters or other Vernier voltage probes that it can induce measurement errors under certain situations.

For example, if the 30V probe is used to measure the potential difference across a 100K resistor (much larger than the input impedance of the sensor), the current flowing to the resistor will be split between the 100K resistor and the 30K internal resistance of the sensor. Most of the current will flow through the sensor, and it will then read about 25% of the expected potential. A multimeter or our Differential Voltage Probe (DVP-BTA) will measure the expected value.

We do not recommend the 30V sensor for use in RC circuits or other high-impedance applications.