Any time the voltmeter probes see the same line (L1 to L1 or L2 to L2), 0 V will be read on the voltmeter because there is no voltage difference between the same lines. So, if the service technician ...

When it comes to electrical circuits, there’s a lot to remember and understand. We've got you covered with this Intro to Circuits BBC Bitesize guide.

The resistor values (R1&R2) in the circuit diagram provide some over-voltage protection then measuring low voltages. Keep it in mind that any input voltage higher than about 55V could fry the Arduino.

This digital thermometer circuit diagram uses a common 1N4148 diode as the temperature sensor. The temperature coefficient of the diode, -2 mV/°C is. ... Set P1 so that the digital voltmeter will ...