Working Principle of Digital Multimeter The basic circuit of a digital multimeter is a header circuit. The basic function it completes is to quantize the input DC voltage (analog) and output; other functions generally require the addition of external circuits. Now the chips of multimeters are getting more and more integrated, and there are fewer and fewer peripheral circuits, which has both advantages and disadvantages. Advantages: high integration, simple external circuits, and fewer quality failures caused by component quality problems; disadvantages: once the chip is broken, the replacement cost is high and troublesome, sometimes you can buy another meter for the cost of replacing a chip, so Generally broken and had to scrap. Digital Multimeter Operation Guide 1. DC Voltage Measurement
1. Insert the black test lead into the COM jack and the red test lead into the V / Ω jack.
2. Put the function switch in the V-range of the DC voltage range, and connect the test probe to the power supply under test to measure the open circuit voltage) or load (measure the load voltage drop), the polarity of the terminal connected to the red test pen will be displayed on the display on. (
note:
1. If you don't know the measured voltage range, put the function switch to the maximum range and gradually decrease.
2. If the display only shows "1", indicating over-range, the function switch should be set to a higher range.
3. "" means do not measure voltages higher than 100, it is possible to display higher voltage values, but there is a danger of damaging internal circuits. 0V
4. When measuring high voltage, extra care should be taken to avoid electric shock.
2. DC current measurement
1. Insert the black test lead into the COM jack. When measuring the maximum current of 200mA, the red test lead is inserted into the mA jack. When measuring the maximum current of 20A, the red test lead is inserted into the 20A jack.
2. Put the function switch in the A-range of the DC current range, and connect the test leads in series to the load to be tested. At the same time the current value is displayed, the polarity of the red lead will be displayed.
note:
1. If you do not know the measured current range before use, put the function switch to the maximum range and gradually decrease.
2. If the display only shows "1", indicating over-range, the function switch should be set to a higher range.
3. It means the maximum input current is 200mA. Excessive current will burn the fuse. It should be replaced again. There is no fuse protection in the 20A range, and the measurement cannot exceed 15 seconds.
3. AC voltage measurement
1. Insert the black test lead into the COM jack and the red test lead into the V / Ω jack.
2. Put the function switch in the range of AC voltage range V ~ range, and connect the test pen to the power supply or load to be tested. The test connection diagram is the same as above. When measuring AC voltage, there is no polarity display.
note:
1. Refer to DC Voltage Note 1.2.4.
2. "" means do not input a voltage higher than 700Vrms, it is possible to display a higher voltage value, but there is a risk of damage to the internal circuit.
4. Measurement of AC current
1. Insert the black test lead into the COM jack. When measuring the maximum current of 200mA, the red test lead is inserted into the mA jack. When measuring the maximum current of 20A, the red test lead is inserted into the 20A jack.
2. Set the function switch to the AC current range A ~ range, and connect the test leads in series to the circuit to be tested.
note:
1. Refer to notes 1, 2, and 3 for DCA measurement.
V. Resistance measurement
1. Insert the black test lead into the COM jack and the red test lead into the V / Ω jack.
2. Place the function switch in the Ω range and connect the test lead to the resistance to be measured.
note:
1. If the measured resistance value exceeds the maximum value of the selected range, the over range "1" will be displayed, and a higher range should be selected. For resistances greater than 1MΩ or higher, the reading will stabilize after a few seconds. normal.
2. When there is no connection, such as an open circuit, the meter displays "1".
3. When checking the impedance of the line under test, make sure to remove all power in the line under test and discharge all capacitors. If the power supply and energy storage components in the circuit under test will affect the accuracy of the line impedance test.
4. The 200MΩ range of the multimeter has 10 words when short-circuited. When measuring a resistance, these 10 words should be subtracted from the measurement reading. For example, when measuring a resistance, the display is 101.0, and 10 words should be subtracted from 101.0. The actual resistance of the device under test is 100.0, that is, 100MΩ.
6. Capacitance test
Before connecting the capacitor to be tested, please note that each time the range is changed, it takes time to reset, and the presence of drift readings will not affect the test accuracy.
1. Place the function switch in the capacitance range C (F)
2. Insert the capacitor into the capacitance test socket
note:
1. The instrument itself has been set up to protect the capacitance file, so there is no need to consider the polarity and charging and discharging of the capacitor during the capacitance test.
2. When measuring capacitance, insert the capacitance into a dedicated capacitance test socket (do not insert into the test lead jack COM, V / Ω).
3. It takes a certain time to stabilize the reading when measuring large capacitance.
4. Unit conversion of capacitance: 1μF = 106pFlμF = 103nF
7. Diode test and buzzer test
1. Insert the black test lead into the COM jack and the red test lead into the V / Ω jack (the polarity of the red test lead is "+"). Set the function switch to the "" position and connect the test lead to the diode to be tested. The reading is positive diode Approximate pressure drop.
2. Connect the test leads to the two ends of the line to be tested. If the resistance between the two ends is less than about 70Ω, the built-in buzzer will sound.
From: http: //
Beauty Display Rack
Beauty Display Rack,Glass Display Floor Stand Unit,Retail Display Rack,Retail Store Display Rack
Dongguan Display Leader Co., Ltd , https://www.displayonestop.com