Introduction to some tests of digital multimeter
(1) Resistance measurement. Adjust the transfer switch to the Ω block, connect the test lead measurement terminal to both ends of the resistance, and then the corresponding indication value can be displayed. If the maximum value "1" (overflow symbol) is displayed, it must be adjusted to the high resistance value position until the display is valid. value.
In order to ensure the accuracy of the measurement, when measuring the resistance on the road, it is best to disconnect one end of the resistance, so as not to form a loop in the circuit when measuring the resistance, which will affect the measurement results.
Note: Online measurement is not allowed when the power is turned on, the power must be cut off and the bulk capacitor must be discharged before measurement.
(2) "DCV" is a direct current voltage measurement. The test end of the test lead must be in reliable contact with the test end (parallel measurement). In principle, adjust the measurement gradually from the high-voltage gear to the low-voltage gear until 1/3~2/3 of the indicated value of the gear, and the indicated value at this time is a relatively accurate value.
Note: It is strictly forbidden to measure large voltages with small voltage gears. It is not allowed to adjust the transfer switch in the energized state.
(3) "ACV" AC voltage measurement. The test end of the test lead must be in reliable contact with the test end (parallel measurement). In principle, adjust the measurement gradually from the high-voltage gear to the low-voltage gear until 1/3~2/3 of the indicated value of the gear, and the indicated value at this time is a relatively accurate value.
Note: It is strictly forbidden to measure large voltages with small voltage gears. It is not allowed to adjust the transfer switch in the energized state.
(4) Diode measurement. Turn the switch to the diode gear, connect the black test lead to the negative pole of the diode, and connect the red test lead to the positive pole of the diode, and then the forward voltage drop value can be measured.
(5) Measurement of transistor current amplification factor hEF. Turn the transfer switch to the "hFE" gear, select the "PNP" or "NPN" position according to the transistor to be tested, and insert the transistor into the test socket correctly to measure the "hee" value of the transistor.
(6) Open circuit detection. Turn the changeover switch to the gear with the buzzer symbol, and the test lead’s test terminal will reliably touch the test point. If the two are lower than 20±lOΩ, the buzzer will sound, indicating that the line is connected. If it does not sound, it should be The line is broken.
Note: It is not allowed to test while the circuit under test is energized.
(7) "DCA" direct current measurement. At 200mA, insert the red test lead into the mA jack; at 200mA
Insert the red test lead into the A jack, and the test end of the test lead must be in reliable contact with the test end (serial measurement). In principle, adjust the measurement gradually from the high current gear to the low current gear until 1/3~2/3 of the indication value of the gear, and the indication value at this time is a relatively accurate value.
Note: It is strictly forbidden to measure large current with low current gear. It is not allowed to adjust the transfer switch in the energized state.
(8) "ACA"—AC current measurement. At 200mA, insert the red test lead into the mA jack; at 200mA, insert the red test lead into the A jack, and the test end of the test lead must be in reliable contact with the test end (serial measurement). In principle, adjust the measurement gradually from the high-current gear to the low-current gear until 1/3~2/3 of the indicated value of the gear, and the indicated value at this time is a relatively accurate value.
