Use and Precautions of Pointer Multimeter and Oscilloscope
(1) Mechanical zero position adjustment: Before use, first check whether the pointer is at zero position, if not, adjust the zero position adjuster so that the pointer is adjusted to zero position.
(2) Correctly connect the test leads: the red test lead should be inserted into the jack marked "+", and the black test lead should be inserted into the "-" jack. When measuring DC current and DC voltage, the red test lead is connected to the positive pole of the measured voltage and current, and the black test lead is connected to the negative pole.
When using the ohm block "Ω" to judge the polarity of the diode, note that the "+" jack is connected to the negative pole of the battery in the meter, and the "-" jack is connected to the positive pole of the battery in the meter.
(3) When measuring voltage, the multimeter should be connected in parallel with the circuit under test; when measuring current, the circuit under test should be disconnected, and the multimeter should be connected in series to the circuit under test. Note: When measuring the current, you should estimate the magnitude of the measured current and select the correct range. The fuse of the MF500 type is 0.3A~0.5A, and the measured current cannot exceed this value. Some multimeters have a 10A range, which can be used to measure larger currents.
(4) Range conversion: the power should be cut off first, and it is absolutely not allowed to change the range with power on; according to the measured position, do not use the current block or ohm block to measure the voltage, otherwise the multimeter will be damaged.
(5) Reasonably select the range block: when measuring voltage and current, the needle should be deflected to more than 1/2 or 2/3 of the full scale; when measuring resistance, the needle should be deflected near the center scale (the design of the electric block is Center scale is standard).
When measuring AC voltage and current, note that the measured voltage must be sinusoidal AC voltage and current, and the frequency of the measured signal cannot exceed the specification on the manual.
When measuring the AC voltage below 10V, you should use the 10V special scale to mark the reading, and its scales are not equidistant.
(6) When measuring resistance, the ammeter should be zeroed first. The method is to short-circuit the two test leads, adjust the "zero adjustment" knob to make the pointer point to zero (note that the zero scale of ohm is on the right side of the dial). If the zero point cannot be adjusted, it means that the voltage of the battery in the multimeter is insufficient, and a new battery needs to be replaced. When measuring a large resistance, both hands cannot touch the resistance at the same time to prevent the measurement error caused by the parallel connection between the resistance of the human body and the resistance to be measured. Every time the range is changed, the zero adjustment must be done again. If the above method cannot be adjusted to zero, the winding resistance of the multimeter (resistance with a resistance of about a few ohms) may be blown, and it needs to be disassembled for maintenance and calibration.
There are multiple scale lines on the dial, corresponding to different measurands, and the value should be read on the corresponding scale line when reading. In order to improve the measurement accuracy, try to keep the pointer in the middle position.
Reading of the measured value: the measured value is obtained by multiplying the reading marked by the pointer during the measurement by the range magnification. When measuring the resistance, be careful not to touch the two test leads or the metal end of the measured resistance, so as not to introduce human body induction resistance and reduce the reading, especially for the R×10K file test.
(7) After using the multimeter, put the switch on the maximum AC voltage position to avoid damage to the meter.
(8) When the multimeter is not used for a long time, the battery should be taken out to prevent battery leakage, corrosion and damage to the internal parts of the multimeter. There are two types of batteries for the multimeter: ordinary AA (1.5v) and laminated batteries (9v). Among them, 9v is used to measure the resistance above 10k and to judge the leakage of small capacitors.
(9) Since the resistance file R×10K of the multimeter uses a 9V battery, components with very low withstand voltage cannot be detected.
