Principle and requirements for multimeter on-off equipment
Almost all multimeters offer an on-off measuring mode that is used to determine if a line is on or off (short circuit). A buzzer and an LED light are typically employed. When the circuit is linked, either the buzzer or the LED light will activate. The multimeter's on/off gear is indicated by the sign in the red box in the figure.
The principle of on-off gear
The internal circuit is activated when the multimeter is set to the on-off position. The black test lead is connected to the internal battery's negative pole, the positive pole is connected to a resistor with a low resistance, and the other end of the resistor is connected to the red test lead. The resistor provides the trigger signal to the internal chirping circuit. The voltage on the trigger resistor inside the meter is high if the two test leads are shorted together or their resistance is low, which causes the beep to be activated.If the resistance between the two test leads is large, then the divided voltage of the internal trigger resistor connected in series is very small, and the beep cannot be triggered.
On-off gear standard
According to the general definition, conductivity is defined as 80 ohms or less; otherwise, it is non-conductivity. In other words, join the multimeter's red and black test leads to the line's two ends. The multimeter will make a sound and believe that the line is conducting if the resistance is less than 80 ohms.
