Talking about Correct Use of Pointer Multimeter
1. Quantitative measurement
In order to reduce the error, before measuring, first check whether the pointer points to the zero position of the voltage (current) scale. If the pointer does not point to this position, you can adjust the mechanical zero adjuster on the cover to make the pointer return to zero, that is, mechanical zero adjustment.
1. Measurement of common physical quantities
(1) Measurement of resistance. Adjust the range switch to the "resistance (Ω)" block, short-circuit the two test leads, and adjust the zero-adjustment potentiometer knob until the pointer points to zero. Then separate the test leads and connect them to the two ends of the measured resistance. In order to reduce the measurement error, select the pointer to stay within the range of 1/3 to 2/3 of the full scale of the resistance dial before reading, otherwise select other appropriate ranges.
(2) Measurement of DC voltage. Adjust the range switch to the "DC voltage (DCV)" block, and connect the red and black test leads to the high potential end and low potential end of the DC circuit under test or the positive and negative ends of the power supply respectively. In order to reduce the measurement error, select the pointer to stay above 2/3 of the full scale of the voltage dial but not exceed its maximum scale before reading, otherwise select another appropriate range.
(3) Measurement of AC voltage. Set the range switch to "AC voltage (ACV ～)", connect the two test leads (without polarity) to the two ends of the AC circuit or power supply under test, and the reading method and range selection method are the same as above.
(4) Measurement of DC current. Set the range switch to the "DC voltage (mA)" position, disconnect the measured circuit first, and then connect the red and black test leads to the two ends of the high potential and low potential of the DC circuit under test respectively. The reading method is the same as the range selection method. (2).
(5) Measurement of alternating current. Since the measured current needs to be disconnected from the circuit under test, and the AC current is generally large, the operation process is more troublesome, so the AC current measurement usually uses a clamp ammeter.
2. Measurement of other physical quantities
(1) Measurement of high-voltage direct and alternating voltages. Adjust the range switch to "2500", connect the "+" pole of the test rod to the 2500V jack for measurement; if it is equipped with a high-voltage probe, it can measure the high voltage of the TV (less than 25kV), and the switch should be set to 50μA during measurement In the gear position, the red and black plugs of the high-voltage probe are inserted into the "+" and "-" jacks of the multimeter respectively, and the measurement can be performed after the grounding clip is connected to the metal bottom plate of the TV.
(2) DC capacitance measurement. First turn the switch to C×10k, short-circuit the two test leads, and calibrate to zero. The capacitance to be measured is connected to both ends of the pen, and the maximum display value of the needle swing is the capacity of the capacitance. If there is a polarized capacitor, it should be connected according to the correct polarity. The reading method and range selection method are the same as those for measuring resistance.
(3) Measurement of DC magnification of ordinary transistors. First turn the switch to R×10hFE (that is, R×10 ohm block), and after zeroing in the same method as the ohm block, insert the NPN or PNP transistor into the N or P socket of the transistor correspondingly, the table
The value indicated by the needle is the DC magnification of the tube.
(4) Inductance measurement. First prepare a standard voltage source of AC 10V/Hz, turn the switch to AC 10V gear, first connect the inductance to be measured to the multimeter in series, and connect to the standard power supply. At this time, the dial (LH) scale value indicates the value to be tested Measure the inductance value.
(5) Audio level measurement. It is used to measure the gain of the amplifier and the loss of line transmission on a certain load impedance, and the measurement unit is expressed in decibels. The measurement method is basically similar to that of AC voltage. When the circuit under test has a DC voltage component, a 0.1μF/250V DC blocking capacitor can be connected in series with the "+" socket.
