Why does the multimeter read 2400hz voltage but the voltage reading on the display is incorrect?
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.
Relevant requirements for multimeters stipulate:
1. The multimeter can not only be used to measure the resistance of the object to be measured, but also the AC and DC voltage can also measure the DC voltage. Some multimeters can even measure the main parameters of transistors and the capacitance of capacitors.
2. The DC current file of the multimeter is a multi-range DC voltmeter. The voltage range can be expanded by connecting the closed-circuit voltage dividing resistor in parallel with the meter head. The DC voltage file of the multimeter is a multi-range DC voltmeter. Connecting the voltage dividing resistor in series with the meter head can expand its voltage range.
3. Different voltage dividing resistors of the multimeter have different corresponding ranges. The head of the multimeter is a magnetoelectric system measuring mechanism, which can only pass through direct current, and use diodes to change alternating current into direct current, thereby realizing the measurement of alternating current.
