Why is the displayed voltage value inaccurate when the multimeter measures 2400hz voltage?
First of all, we need to understand the effective value of the multimeter test value. Our current commonly used multimeters include pointer multimeters and digital multimeters. Pointer multimeters have an AC voltage range of 10v to 1000v and a minimum scale of 0.2v. Looking at the schematic diagram, the AC voltage file is a simple rectification circuit designed for 50Hz (60Hz in the United States and Japan) AC voltage test. The internal circuit includes rectifier diodes without considering high-frequency characteristics. If the measured signal frequency exceeds 1KHz, it will be Will not be allowed.
The inside of the digital multimeter is an IC for measurement. It doesn’t make much sense to release the schematic diagram. The high-frequency characteristics of the AC voltage file are related to the bandwidth of the IC’s operational amplifier (OP) and the IC’s AD conversion rate. There will be more content to clarify the parameters, so let’s just mention it for now.
If we want to accurately test the signal in the 2.4KHz frequency band, we need to use an audio millivolt meter. This device is a commonly used device for audio measurement. It used to be pointer type, but now it is digital.
How to Repair a Multimeter
The repair method of the pointer multimeter is as follows: 1: If the multimeter is damaged due to accidentally hitting the wrong gear, you can generally check whether the fuse in the multimeter is blown. If it breaks, just replace it. If it doesn't break, it's a circuit problem. Generally, it is repaired like this: first turn on the multimeter, set the gear to the gear you burned out, and then check whether the resistance on the gear is damaged. If it is damaged, just change it. [Because the resistors in the multimeter are all non-standard resistors, and they are all high-precision resistors with 5 color rings, it is difficult to buy, you can use the method of series and parallel to get the required resistance value], if it is not good, it is generally The meter head was damaged by overload.
