True-rms digital multimeter (True-rms): A digital multimeter that can accurately measure the effective values of sine waves and non-sinusoidal waves.

Current-shunt: A low-value resistor in a digital multimeter used to measure current. A digital multimeter measures the voltage across it and uses Ohm's law to calculate the current value.

Average Responding Digital Multimeter (Average Responding): It can accurately measure sine waves, but it is not accurate enough when measuring non-sinusoidal waves.

Non-sinusoidal waveform: waveforms such as pulse sequence, square wave, triangle wave, sawtooth wave, peak wave, etc.