Why can't a multimeter measure the polarity of an alternating current?
The so-called alternating current refers to its polarity is alternately changing, and the speed of change is very fast, whether it is a pointer or a little more advanced general digital multimeter, can not respond to its instantaneous polarity, its polarity is the number of changes per unit of time is called the frequency, which is the unit of Hertz, which is to commemorate the famous physicists Mr. Hertz and named the unit of physics. Because the polarity of this power supply alternates so with a general multimeter simply can not measure its polarity, if there is a need to understand the polarity of a certain moment, can also be said to be the polarity of its instantaneous the easiest way, that is specifically for the observation of alternating current or direct current pulses of electronic instruments oscilloscopes.
The direction of alternating current changes at any time, do not speak of polarity. If the measurement of the fire line zero line, you can play the multimeter to the AC voltage of the highest grade, a hand pinch the black pen head, with the red pen probe wire, the pointer deflection is the fire line, does not deflect is the zero line. In addition, some digital multimeter nowadays, with the function of the power test pen.
Alternating current is the size and direction of the periodic changes in current, no polarity, only frequency, the frequency of our alternating current is 50 hertz, that is, the current changes back and forth 50 times per second, the direction changes 100 times, the question itself is a problem.
Multimeter can not measure capacitance how to do
If you have a weak foundation can be repaired, of course, a new one is also a good choice, after all, the table is not expensive.
Multimeter capacitance file is generally used to limit the fixed frequency AC signal through a resistor, added to the capacitor for measurement, and then the feedback signal through the op-amp amplification limiting added to the AD conversion circuit. The focus should be to check the AC signal oscillator circuit, capacitor socket, op-amp amplifier path, range switch, and current limiting resistor filter capacitor.
If you have an oscilloscope is half the effort, measuring the waveform of each circuit can easily determine the scope of the fault, and then find out the specific components.
Definitely can measure the capacitance, pointer 10k block, digital meter can be measured. Measured according to the principle of capacitance charging and discharging!
