The exploring electrode detects a voltage of −20 μV. The output voltage is 50 μV. What voltage did the reference electrodes detect at this time?

To determine the voltage detected by the reference electrodes, it's important to understand the relationship between the exploring electrode voltage, the output voltage, and what the reference electrodes report.

The output voltage is calculated by taking the difference between the exploring electrode voltage and the reference electrode voltage. In this scenario, the output voltage is 50 μV, indicating that the sum of the exploring and reference electrode values leads to that output.

Given that the exploring electrode detects a voltage of -20 μV, we can express the calculation as follows:

Output voltage = Voltage of exploring electrode - Voltage of reference electrode.

Substituting in the given values, we have:

50 μV = -20 μV - Voltage of reference electrode.

To find the voltage of the reference electrodes, we rearrange the equation:

Voltage of reference electrode = -20 μV - 50 μV = -70 μV.

This calculation shows that the reference electrodes detected a voltage of -70 μV at that time. Therefore, the correct answer indicates that the voltage detected by the reference electrodes is indeed -70 μV.