How to measure three-phase voltage with a multimeter
How to use the first multimeter? As shown in the figure below for a digital multimeter, select the jack, to choose with V and with COM end of the two jacks on it, as shown in the figure insert these two holes, this must not get it wrong, otherwise it is very dangerous. Then it is the range and gear selection, some multimeter is only gear without the need to individually select the range, but the figure shows this must be played to the AC voltage gear, that is, the symbol for the V followed by a wavy line, and range selection than you want to measure the voltage level.
The second measurement when the pen contact which two wires? Usually three-phase electricity in accordance with national standards are respectively yellow, green and red three colors to indicate the ABC three-phase, if you want to measure the AB two-phase voltage, put the meter pen to the yellow and green line can be, pay attention to the positive and negative poles do not have to be divided. Similarly, if you want to measure the BC phase voltage, just contact the green and red wires respectively. By analogy, contact the yellow and red wires is to measure the AC phase voltage.
The multimeter will be switched to the measurement of the voltage block, the multimeter with the red and black pens to measure the three-phase power in two-phase voltage to see if it is in the 380V or so, but also to see whether the three-phase voltage is accurate and balanced. When performing these tasks. Be sure to pay attention to safety. This kind is a kind of protection for oneself
Pointer multimeter frequency measurement method
Want to use the multimeter to measure the frequency, you can convert the frequency to voltage to measure. Some new pointer multimeters have a frequency measurement function. It should be noted that if you want to measure the frequency, you must convert the measured frequency into a DC voltage signal to complete the frequency conversion.
Here we will introduce a frequency measurement method. This method uses a pointer multimeter (DC millivolt meter with a full scale of 200mV) and a frequency/voltage converter. Suspicious measurement of 10Hz ~ 20kHz range of frequency, measurement accuracy of up to 2%, the measured frequency signal RMS value of 50mV ~ 10V.
Measurement Principle
First, the frequency/voltage converter is utilized to convert the measured frequency signal into DC voltage, which is then sent to the 2.5V voltage gear. Measurement circuit shown below, the circuit mainly contains operational amplifier TL061, CMOS six inverter CD4069, CMOS timer ICM7555.
