Usage and Precautions of Analog Multimeters and Oscilloscopes
(1) Mechanical zero position adjustment: Before use, check whether the pointer is at zero position. If it is not at zero position, adjust the zero position adjuster to adjust the pointer to zero position.
(2) Correctly connect the probes: The red probe should be inserted into the socket marked with a "+", and the black probe should be inserted into the socket marked with a "-". When measuring DC current and DC voltage, connect the red probe to the positive pole of the measured voltage and current, and connect the black probe to the negative pole.
When using the ohm range "Ω" to determine the polarity of a diode, note that the "+" socket is connected to the negative terminal of the battery inside the meter, and the "-" socket is connected to the positive terminal of the battery inside the meter.
(3) When measuring voltage, the multimeter should be connected in parallel with the circuit being tested; When measuring current, disconnect the circuit being tested and connect a multimeter in series with it. Attention: When measuring current, the size of the measured current should be estimated and the correct range should be selected. The MF500 fuse has a range of 0.3A to 0.5A, and the measured current cannot exceed this value. Some multimeters have a 10A gear, which can be used to measure larger currents.
(4) Range conversion: The power should be turned off first, and it is absolutely not allowed to change the range while the power is on; According to the measurement being placed in the correct position, do not use current mode or ohm mode to measure voltage, otherwise it will damage the multimeter.
(5) Reasonable selection of range gear: When measuring voltage and current, the pointer should be deflected to at least 1/2 or 2/3 of the full scale; When measuring resistance, the pointer should be deflected to near the center scale (the design of the resistance gear is based on the center scale).
When measuring AC voltage and current, it is important to note that the measured signal must be a sinusoidal AC voltage and current, and the frequency of the measured signal must not exceed the specifications in the manual.
When measuring AC voltage below 10V, the reading should be marked with a 10V dedicated scale, which is not equidistant.
(6) When measuring resistance, the meter should be zeroed first. The method is to short-circuit the two probes and adjust the "zero" knob to make the pointer point to zero (note that the zero scale of the ohm is on the right side of the dial). If it cannot be adjusted to zero, it indicates that the battery voltage in the multimeter is insufficient and a new battery needs to be replaced. When measuring high resistance, both hands should not touch the resistance at the same time to prevent measurement errors caused by parallel connection of human resistance and the measured resistance. Every time the range is changed, it needs to be reset to zero. If the above methods cannot zero, it is possible that the winding resistor of the multimeter (a resistor with a resistance of several ohms) will burn out and need to be disassembled for repair and calibration.
There are multiple scale lines on the dial, corresponding to different measurements. When reading, the values should be read on the corresponding scale lines. To improve measurement accuracy, try to keep the pointer in the middle position as much as possible.
Reading of measurement value: Multiply the reading marked by the pointer during measurement by the range multiplier to obtain the measured value. When measuring resistance, be careful not to touch the two probes or the metal end of the measured resistor with your hands, in order to avoid introducing human induced resistance and reducing the reading, especially for R × 10K testing, which has a significant impact.
(7) After using the multimeter, place the conversion switch in the maximum AC voltage position to avoid damaging the instrument.
(8) When the multimeter is not in use for a long time, the battery should be removed to prevent battery leakage, corrosion, and damage to the parts inside the multimeter. The multimeter has two types of batteries: regular No. 5 (1.5v) and stacked battery (9v). Among them, 9V is used to measure resistance above 10k and to distinguish the leakage situation of small capacitors.
(9) Due to the use of a 9V battery in the resistance range R × 10K of the multimeter, it is not possible to detect components with very low withstand voltage values.
