Multimeter AC gear for voltage measurement is series or parallel connection
Multimeter voltage measurement is in parallel, the measurement of current is in series, both AC and DC are so, the multimeter voltage gear internal resistance close to infinity, so if you choose to use the voltage gear to connect the multimeter in series in the circuit in fact, the circuit is not the current or that the current is particularly small, so that the measurement of what data, for the current gear internal resistance close to 0, so he is not too much to affect the back of the series in the circuit! Electrical work.
But if you choose to use the wrong current file connected in parallel in the circuit, such as the main question asked in this case, if the voltage file into a current file connected in parallel at both ends of the 220V power supply, it is quite dangerous, a direct short circuit, it is possible to burn the multimeter or the line are burned out.
Voltage file measurement is relatively safe, even if the series connection in the circuit will not appear like the current file connected to the wrong kind of situation harm so much, we use the multimeter was trying to measure out some data, so before measuring must think about how to measure.
Whether series or parallel first to figure out the multimeter to measure the principle of AC voltage, the multimeter head can only pass DC voltage, that is, can only measure DC voltage, then why can measure AC voltage, that is because of the multimeter internal rectifier circuit, using the diode's unidirectional conductivity will be the AC signal into a DC signal, so you can measure the AC voltage, that is to say, the multimeter AC file measurement Home 220V voltage, is a parallel circuit.
AC voltage measurement principle: the multimeter to measure AC voltage, because the multimeter has a half-wave rectifier circuit, when to measure AC voltage, the AC voltage will be rectified into DC voltage and then through the two heads, and ultimately according to the size of the DC to measure the AC voltage, and the multimeter shows the AC voltage is not the instantaneous value of the alternating current, but a period of time in the average, which means that the effective value. That is to say, the effective value. In fact, the internal multimeter is not only so simple, but also through the operational amplifier to amplify the signal, after sampling analogue-to-digital conversion, the final result is displayed on the screen.
Measurement of home 220V voltage, just choose a good AC range, the following Fluke digital multimeter description, black and red pens inserted into the appropriate position, directly across the utility zero fire line, do not need to distinguish which is the fire line which is the zero line, you can read out the voltage directly!
