The difference between the diode mode and the on/off mode of a multimeter

The diode mode is mainly used to measure the forward voltage drop of the diode, while the buzzer mode, also known as the on/off mode, is mainly used to measure the continuity of the circuit. Some multimeters combine the buzzer mode with the diode mode, while others separate these two modes.

The diode block mainly generates a voltage source of about 2.8V inside the A/D converter, which is applied to the V Ω hole and COM hole. When you connect the red and black probes to the two ends of the tested diode, it is mainly this 2.8V voltage source to measure the forward and reverse conduction voltage drop of the diode.

The on-off mode mainly relies on the operational amplifier to control the buzzer to sound. If the resistance of the tested circuit is lower than 70 ohms, some are 60 ohms, and this resistance depends on the threshold of the operational amplifier. That is to say, we can change the buzzer's sound resistance value by changing the operational amplifier's sound threshold, for example, we can make it sound at 50 ohms.