Multimeter on-off principle and standard
The on-off mode is a measurement mode that almost all multimeters have to measure whether the line is on or off (short circuit). It is usually coupled with a buzzer and an LED. A buzzer sounds or an LED lights up to indicate that the line is on. As shown in the figure, the red box mark is the on-off mode of the multimeter.
On-off principle
Multimeter dialled to the on-off position, was connected to the internal circuit is: the black pen to the negative terminal of the internal battery, the positive terminal of the battery connected to a small resistance resistor, the other end of the resistor connected to the red pen. The internal chirp circuit then obtains a trigger signal from the resistor. If the two pens are short-circuited or the resistance between them is small, then the voltage on the trigger resistor inside the meter will be higher, thus triggering the chirp. If the resistance between the two pens is large, then the partial voltage across the internal triggering resistor in series is small and the chirp cannot be triggered.
On-Off Criteria
The general definition is 80 ohms and below is on, otherwise it is not on. In other words, connect the red and black pens of the multimeter on both sides of a line, if the resistance of this line is lower than 80 ohms, the multimeter will sound and consider this line to be on.
