Introduction to the multimeter's header
The head of the multimeter is a sensitive galvanometer. The dial on the head is printed with various symbols, scale marks and values. The symbol A-V-Ω indicates that the ammeter is a multimeter that can measure current, voltage and resistance. There are multiple scale lines printed on the dial, among which the one marked with "Ω" on the right is the resistance scale line, the right end is zero, the left end is ∞, and the scale value distribution is uneven. The symbol "-" or "DC" means direct current, "~" or "AC" means alternating current, and "~" means the scale line shared by AC and DC. Several rows of numbers under the scale line are the scale values corresponding to the different positions of the selector switch.
There is also a mechanical zero adjustment knob on the meter head to correct the zero position of the pointer at the left end.
Why can't the multimeter measure high frequency AC signal
Inside the multimeter, some non-pure resistance components are involved in the measurement of AC, such as the pointer coil of the pointer meter, the DC isolation capacitor of the digital meter, etc., and its impedance is related to the frequency and waveform of the AC. Therefore, the calibration of the multimeter is calibrated with a certain frequency and waveform of alternating current as the standard. If you use it to measure alternating currents of other frequencies and waveforms, the readings will be inaccurate.
Precautions for use
① Adjust the "zero point" (only for mechanical watches). Before using the watch, first check that the pointer is on the "zero position" at the left end. If not, you should slowly turn the "starting zero position" in the center of the case with a small screwdriver Adjust the screw so that the pointer points to the zero position.
②The multimeter should be placed horizontally when in use (machine only).
③Before the test, determine the measurement content, and turn the range conversion knob to the corresponding gear for the measurement shown, so as not to burn the meter head. If you do not know the size of the measured physical quantity, start the test with a large range.
④The test leads should be correctly inserted into the corresponding sockets.
⑤During the test, do not rotate the gear changing knob arbitrarily.
⑥ After use, be sure to adjust the gear change knob of the unused meter to the maximum range gear of the AC voltage.
⑦ When measuring DC voltage and current, pay attention to the positive and negative poles of the voltage, the flow direction of the current, and connect (when) with the test leads correctly.
