Whether the multimeter's voltage is wired in series or parallel
The voltage of the multimeter is connected in parallel, and the current is connected in series, whether it is AC or DC, the internal resistance of the voltage range of the multimeter is close to infinity, so if the voltage range is selected and the multimeter is connected in series in the circuit, there is actually no current in the circuit or It is said that the current is very small, so that no data can be measured. For the current range, the internal resistance is close to 0, so connecting it in series in the circuit will not affect the operation of the following electrical appliances.
However, if the wrong current gear is selected and connected in parallel in the circuit, such as the situation asked by the subject, if the voltage gear is changed to a current gear and connected in parallel to both ends of the 220V power supply, it is quite dangerous, and it is directly short-circuited, and it is possible to use a multimeter or The lines are all burnt out.
The voltage file is relatively safe to measure. Even if it is connected in series in the circuit, it will not be as harmful as the wrong connection of the current file. We use a multimeter to measure some data, so we must think about it before measuring. Measurement.
Whether to connect in series or in parallel, we must first understand the principle of the multimeter to measure AC voltage. The head of the multimeter can only pass through DC voltage, that is, it can only measure DC voltage. Then why can it measure AC voltage? It is because there is a rectifier circuit inside the multimeter. The unidirectional conductivity of the diode turns the AC signal into a DC signal, so the AC voltage can be measured, that is to say, the AC gear of the multimeter measures the household 220V voltage, which is a parallel circuit.
AC voltage measurement principle: When the multimeter measures the AC voltage, because there is a half-wave rectification circuit inside the multimeter, when the AC voltage is to be measured, the AC voltage is rectified and turned into a DC voltage and then passed through the two meters, and finally according to the DC voltage. The magnitude of the AC voltage is measured, and the AC voltage displayed by the multimeter is not the instantaneous value of the AC current, but the average value over a period of time, that is to say, the effective value. In fact, the inside of the multimeter is not only that simple, but also needs to amplify the signal through the operational amplifier, and perform analog-to-digital conversion after sampling, and the final result is displayed on the screen.
When measuring the household 220V voltage, you only need to select the AC range. The following is a description of the Fluke digital multimeter. The black and red test leads are inserted into the corresponding positions and directly connected to the neutral and live wires of the mains. There is no need to distinguish which is the live wire and which is the neutral wire. , the voltage can be read directly.
