FOT

Digital multimeter to measure the voltage?

by:FOT     2020-11-16
Is one of the most basic tasks of digital multimeter measure the voltage. The typical dc power source is battery, such as used in the car battery. The ac power is usually produced by the generator. Residence in the wall socket is a common source of ac voltage. Some devices can be ac change to dc. For example, connected to the ac socket on the wall of the TV, stereo equipment, electronic equipment such as video and computer is the so-called converts ac voltage to dc voltage rectifier. The dc voltage for the equipment of the power electronic circuit. When the circuit breakdown, the first step is usually to test power supply voltage is correct. If there is no voltage or voltage is too high or too low should solve the problem of voltage before further investigation. Associated with the ac voltage waveform or a sine wave, or is a sine wave ( Sawtooth wave and square wave, corrugated, etc. ) 。 High quality digital use table can display the voltage waveform 'RMS values (' Root mean square value) 。 The RMS value is the effective value of ac voltage or dc value equivalent. Most digital multimeter is 'average response' model, but in the case of a pure sine wave ac voltage signal is given precise number of RMS. The average response multimeter can't accurately measure non-sinusoidal signal. To accurately measure the sine signal, can use until the rules when the wave number can give a 'true RMS' digital multimeter. Crest factor is the ratio of the peak and RMS values of signals. For pure sine wave, the ratio of 1. 414; But the value is often much more ( For example, for current pulse rectifier) 。 As a result, the average response of the multimeter reading is often much lower than the actual RMS values. Signal frequency can limit the ability of digital multimeter measuring ac voltage. Most multimeters can accurately measure from 50 hz to 500 hz frequency voltage, but the digital multimeter ac measurement bandwidth may be a few hundred thousand Hertz. The multimeter because can 'see' more complex communication signals, reading may be on the high side. Digital multimeter ac voltage and current accuracy parameter should be specified frequency range and accuracy of this range. How to make voltage measurement 1. According to the needs, select V ~ ( Communication) Or V ( Dc) Gears. 2. Put the black test probe COM input jack. Put the red test probe V input jack. 3. If digital multimeter can only manual transformation range, please select the highest range, so as not to let the input overload. 4. Across the load or power supply ( With the circuit in parallel) Contact with the circuit, the probe tip. 5. See the readings, be sure to pay attention to the unit of measure. Note: in order to obtain the correct polarity ( ±) Dc readings, please put the red test probe in contact with the circuit is extreme, the black probe and negative minus sign, indicating negative polarity. When using analogue multimeter, may will be multimeter damage. Note: 1/1000 v = 1 mv1000v = 1 kv high voltage probe can be used in the maintenance of television or a cathode ray tube, the voltage can reach 40 kv ( See figure 3) 。 Caution: these probes are not suitable for electrical equipment measurement applications, in these applications, in addition to the high voltage, accompanied by high energy. They are suitable for low-power applications.
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