What problems should be paid attention to when measuring voltage with a digital multimeter?
The digital multimeter can be used to measure DC and AC voltage, DC and AC current, resistance, capacitance, inductance, frequency, battery, diode, triode hFE and continuity test, and has an automatic power-off function. The circuit design of the whole machine is based on large-scale integrated circuits The dual-integral A/D converter is the core, and it is equipped with a whole-process overload protection circuit, making it a tool with superior performance. It is the first choice for laboratories, factories, schools and electronics enthusiasts.
(1) Precautions before operation
(1) Put the ON-OFF switch in the ON position, check the 9V battery, if the battery voltage is insufficient, " " or "BAT" will be displayed on the display, at this time, the battery should be replaced; if not, follow the steps below .
the
(2) The △ next to the test lead jack! The symbol indicates that the input voltage or current should not exceed the marked value, which is to protect the internal circuit from damage.
(3) Before the test, the function switch should be placed on the required range.
(2) Notes on voltage measurement
(1) If you do not know the measured voltage range, set the function switch to a large range and gradually reduce the range (you cannot change the range during measurement).
(2) If "1" is displayed, it means over-range, and the function switch should be set to a higher range.
(3) △! Indicates that do not input a voltage higher than the multimeter requires, it is only possible to display a higher voltage, but there is a danger of damaging the internal circuit.
(4) When measuring high voltage, special attention should be paid to avoid electric shock.
(3) Precautions for current measurement
(1) If you do not know the measured current range before use, set the function switch to the maximum range and gradually reduce the range (the range cannot be changed during the measurement).
(2) If the display only shows "1", it means over-range, and the function switch should be set to a higher range.
(3) △! The above indicates that the maximum input current is 200mA or 20A (10A), depending on the socket used. Excessive current will burn out the fuse, and the 20A (10A) range has no fuse protection.
(4) The maximum test voltage drop is 200mV.
(4) Precautions for resistance measurement
(1) If the measured resistance value exceeds the maximum value of the selected range, it will display over-range "1", and a higher range should be selected. For resistances greater than 1 MΩ or higher, it will take a few seconds for the reading to stabilize. This is normal for high resistance readings.
(2) When there is no input, such as an open circuit, it will display "1".
(3) When checking the internal line impedance, ensure that all power supplies of the line under test are powered off and all capacitors are discharged.
(4) When 200MΩ is short-circuited, there are about four characters, which should be subtracted from the reading when measuring. For example, when measuring l00MΩ resistance, the display is 101.0, and the fourth character should be subtracted.
(5) Precautions for capacitance testing
(1) The instrument itself has set up protection for the capacitance gear. During the capacitance test process, there is no need to consider the polarity of the capacitance and the charging and discharging of the capacitance.
(2) When measuring capacitance, put the capacitance into the capacitance test socket (do not measure through the test lead jack).
(3) When measuring large capacitance, it takes some time to stabilize the reading.
(4) Unit: 1pF=10-6μF, : 1nF=10-3μF,
(6) Precautions for digital multimeter maintenance
The digital multimeter is a precision electronic instrument, do not change the circuit at will, and pay attention to the following points:
① Do not use beyond the range.
②Do not connect the voltage signal in the resistance or diode mode.
③ Please do not use this watch when the battery is not installed or the back cover is not tightened.
④ Only after the test lead is removed from the multimeter and the power supply is cut off, can it be replaced
Batteries and fuses. Battery replacement: Pay attention to the usage of the 9V battery. If you need to replace the battery, open the screw on the back cover and replace it with the same type of battery. When replacing the fuse, please use the same type of fuse.
