What's wrong with a digital multimeter that shuts off when using the peak-oh stop?
Can not be ruled out is that the battery does not have much power, with the buzzer gear, the buzzer is an inductive load, the instantaneous voltage may be relatively large, which may pull down the battery does not have much power, resulting in the main chip voltage is not enough to directly shut down!
If you change the battery or so, may be the buzzer or related drive circuit short circuit and leakage caused by, there is no need to toss it, a multimeter is not a few dollars, spend more than the time.
Or simply replace a buzzer to try, if not, just buy a new one.
Digital multimeter in the use of the buzzer file when the automatic shutdown generally have two cases, one is the multimeter battery is old, the power consumption of the buzzer file work leads to a significant reduction in the battery voltage, so that the multimeter automatically shut down; another situation is the buzzer file is faulty, the file works when the current is very large, resulting in a significant reduction in the battery voltage, which makes the multimeter shut down. Here we introduce the circuit working principle and fault repair of digital multimeter buzzer gear in detail.
In the buzzer file test circuit pass, if the measured resistance Rx resistance value ≤ 70 Ω (also set to other resistance values), LM324 ① foot output a high level, so that the CD4011 composed of voltage-controlled audio oscillator work, piezoelectric ceramic chip emits a beep, and at the same time, the LED indicator also began to light up.
General digital multimeter other gear operating current is mostly within 10mA, and buzzer gear work due to the piezoelectric ceramic chip and indicator power consumption is large (relatively speaking), if the multimeter's batteries with the old, at this time, it may lead to a significant reduction in battery voltage, so that the multimeter shutdown.
In addition, if the buzzer file CMOS gate circuit CD4011 or piezoelectric ceramic chip failure will lead to a significant increase in power consumption of the entire buzzer file, which will also lead to automatic shutdown of the multimeter. I have previously repaired the buzzer file power consumption failure, mostly CD4011 or piezoelectric ceramic chip problem. General piezoelectric ceramic chip has a slight short circuit at both ends, will lead to the buzzer file sound reduction and power consumption increases.
Digital multimeter piezoelectric ceramic chip as shown in the figure above. This piezo is usually equipped with an acoustic chamber to increase the volume of the sound. A common failure of piezoelectric ceramic discs is that the surface ceramic layer falls off.
The buzzer mode of digital multimeter is usually combined with the diode mode, as shown in the figure above. When using the buzzer to test the circuit, set the range switch to the diode position.
