Digital multimeters

All digital meters contain a battery to power the display so they use virtually no power from the circuit under test. This means that on their DC voltage ranges they have a very high resistance (usually called input impedance) of 1M or more, usually 10M, and they are very unlikely to affect the circuit under test.

Typical ranges for digital multimeters like the one illustrated:
(the values given are the maximum reading on each range)

• DC Voltage: 200mV, 2000mV, 20V, 200V, 600V.
• AC Voltage: 200V, 600V.
• DC Current: 200µA, 2000µA, 20mA, 200mA, 10A*.
  *The 10A range is usually unfused and connected via a special socket.
• AC Current: None. (You are unlikely to need to measure this).
• Resistance: 200, 2000, 20k, 200k, 2000k, Diode Test.

Digital meters have a special diode test setting because their resistance ranges cannot be used to test diodes and other semiconductors.