Why can't the square wave signal amplitude be measured with an AC multimeter?
Internationally, the frequency with high and low changes above 1Hz is called alternating current, the symmetrical duty change is called sine, the linear change with radian is called S wave sine, and the regular rate change is called linear, even if it is not proportional , as long as there is regularity, it is also linear. The power frequency power we use is 220vS wave sine. Although it looks like a triangle wave, it is also a standard linear sine wave.
There is neither frequency nor voltage index, and there is no definition of millivolt meter, so it is impossible to give a positive answer.
It can be understood why a square wave with a certain frequency cannot be displayed on an instrument with a resolution of millivolts.
All instruments are DC, and the AC is measured after the DC meter is rectified.
1. Directly using a millivolt-level meter cannot display alternating current, no waves or volts, and it will not move after shaking. This is because the magnetic steel of the meter head cannot quickly identify high-frequency alternating current. It is a permanent magnet with coercive force and cannot be demagnetized quickly. Only when the meter changes slowly will the meter shake. In addition, the millivolt-level square wave cannot be measured without amplification, and the driving force is too small. It can be measured by an electronic millivolt meter and an oscilloscope, because both instruments have their own amplifiers.
2. When the frequency does not correspond to the instrument, it cannot be measured.
3. Millivolt-level AC signals cannot be rectified to the instrument. It needs at least 0.3v, that is, more than 300 millivolts, to pass through the germanium diode dead zone.
Fourth, the millivolt signal is measured with a single-arm or double-arm bridge, Whiston bridge.
5. The alternating current measured by the instrument is the effective value, and the positive square wave can only measure half the voltage of the amplitude, which is the average value. Note that it is a proportional effective value, and the 1:1 square wave is the average value, which is equal to the effective value.
It is possible, but the swing speeds up. If you have experience, you can immediately judge that only the signal is a pulse signal, which is a square wave. (Some projects require high penetrating power. Square wave measurement is also necessary to complete.) We started to study the application of square wave very early, what is the rising edge, falling edge, how to generate a sharp pulse from mS to uS, and it is composed of analog components , for a long time.
