The principle and standard of on/off shifting of a multimeter
On/off mode is a measurement mode that almost all multimeters have, used to measure the continuity (short circuit) of a circuit. Generally, it is combined with a buzzer and LED light. The buzzer makes a sound or the LED light is on, indicating that the circuit is conductive. As shown in the figure, the symbol inside the red box is the on/off range of the multimeter.
On/off gear principle
When the multimeter is set to the on/off position, the internal circuit that is connected is: the black probe is connected to the negative terminal of the internal battery, the positive terminal of the battery is connected to a resistor with a small resistance value, and the other end of the resistor is connected to the red probe. The internal buzzer circuit obtains a trigger signal from the resistor. If the two probes are short circuited or the resistance between them is small, then the voltage on the triggering resistor in the meter will be higher, triggering a beep. If the resistance between the two probes is large, then the partial voltage of the internal trigger resistor in series is small, and it cannot trigger a beep.
On/off gear standard
The general definition is that 80 ohms or less is conductivity, otherwise it is non conductivity. That is to say, connect the red and black probes of the multimeter to both sides of a circuit. If the resistance of this circuit is less than 80 ohms, the multimeter will make a sound and consider the circuit to be conductive.
