The basic use of pointer multimeter of pointer multimeter
(1) Measurement of DC current
Multimeter generally has 1mA, 10mA, 100mA three DC current range block, the choice of range should be based on the size of the current in the circuit. If you do not know the size of the current, you should first select the highest range block, and then gradually reduce to the appropriate range.
When measuring DC current, first disconnect the corresponding part of the circuit, and then connect the multimeter pens at the two ends of the breakpoint, the red pen is connected to the breakpoint connected to the positive pole of the power supply, and the black pen is connected to the breakpoint connected to the negative pole of the power supply. When reading, the DC current block should read the value of the second scale line, if you choose 100mA block, the third line of numbers under the scale line can be used, and the reading can be multiplied by 10.
(2) AC current measurement
Usually, the multimeter is only set up 1 to 2 blocks of AC current test stops, and is only suitable for measuring the power supply internal resistance or the circuit under test has a high impedance, the frequency of 3kHz below the low-frequency current. In order not to affect the waveform and working state of the circuit under test, the AC current block of the multimeter must adopt symmetrical full-wave rectification.
Measurement, in the measured circuit into a string of low-value precision sampling resistor, and then the multimeter's AC voltage block and connected to the sampling resistor at both ends, by reading out the AC voltage at both ends of the resistor is converted to the current of the circuit under test.
(3) Measurement of voltage
Measurement of AC and DC voltage, should be used respectively AC voltage block and DC voltage block, the range selection and measurement of the same current. When measuring, connect the multimeter with the measured circuit in parallel, connect the red pen to the measured circuit and the positive pole of the power supply, connect the black pen to the measured circuit and the negative pole of the power supply, and read out the voltage value.
Note: DC voltage block scale line is the second scale line, with the 10 block, the third line of figures under the scale line can be used to read out the measured voltage value directly.
(4) Measurement of resistance
Multimeter generally have R × 1, R × 10, R × 100, R × 1k, R × 10k five ranges. Before measurement, the first two pens shorted, while adjusting the "ohm zero knob", so that the pointer just to the right of the ohm scale position. In order to ensure the accuracy of the measurement, every time you change the multiplier block, you need to carry out an ohm zero adjustment.
Measurement, the two pens and the measured resistor ends of the contact, observe the meter readings multiplied by the multiplier, that is, the resistance value of the measured resistor.
