Why does the digital multimeter shut down when using peak mode?
It cannot be ruled out that the battery is low on power. When using the buzzer mode, the buzzer is an inductive load, and the instantaneous voltage may be relatively large. This may pull down the battery that does not have much power, causing the main chip to shut down directly due to insufficient voltage.
If the problem persists after replacing the battery, it may be caused by a short circuit or leakage in the buzzer or related driving circuit. There is no need to worry anymore. A multimeter costs only a few dollars and takes a lot of time.
Or simply try replacing a buzzer. If it doesn't work, just buy a new one.
There are generally two situations when a digital multimeter automatically shuts down when using the buzzer setting. One is that the battery of the multimeter is worn out, and the buzzer setting that consumes more power causes the battery voltage to drop significantly, causing the multimeter to automatically shut down; Another situation is that the buzzer gear is faulty. When this gear is working, the current is very large, causing the battery voltage to drop significantly, causing the multimeter to shut down. Below we will introduce in more detail the working principle of the digital multimeter buzzer circuit and troubleshooting.
A micropower four-2 input NAND gate is connected here to form a voltage-controlled audio oscillator. When using the buzzer mode to test circuit continuity, if the resistance of the resistor Rx under test is ≤70Ω (sometimes set to other resistance values), pin ① of LM324 outputs a high level, causing the voltage-controlled audio circuit composed of CD4011 to The oscillator works, the piezoelectric ceramic piece buzzes, and at the same time, the LED indicator light starts to light up.
Generally, the working current of other settings of a digital multimeter is mostly within 10mA. When the buzzer setting is working, the piezoelectric ceramic chip and the indicator light consume a large amount of power (relatively speaking). If the battery of the multimeter is used up, it may occur at this time. This causes the battery voltage to drop significantly, causing the multimeter to shut down.
In addition, if the CMOS gate circuit CD4011 or the piezoelectric ceramic chip of the buzzer gear fails, the power consumption of the entire buzzer gear will increase significantly, which will also cause the multimeter to automatically shut down. The author has previously repaired the problem of high power consumption in the buzzer mode. Most of the problems were caused by the CD4011 or the piezoelectric ceramic chip. Generally, when there is a slight short circuit at both ends of the piezoelectric ceramic piece, the sound of the buzzer will be reduced and the power consumption will be increased.
