Why does a multimeter measure resistance and adjust it to zero every time
The zero adjustment of a multimeter refers to the mechanical meter saying that when measuring resistance, it is necessary to zero every time. If not, the measured resistance value is inaccurate. There is no need to adjust the voltage and current to zero. If it cannot be zeroed, it indicates that the hairspring in the meter head is aging and its rebound is not good. At this point, there is a zero adjustment knob in the center of the meter head that can be gently adjusted
1. Every electronic amateur can't do without a multimeter. The digital multimeter you're talking about relies on a 1.5V battery installed inside to provide resistance current limiting for the needle to move. I disassembled and installed several pointer meters and many meter heads, with the base of the pointer connected to the center of the meter head and a magnet with a diameter of a few millimeters wrapped around a coil on the magnetic column. The needle is connected to the base of the pointer with an oil wire, and the other end is fixed. When the knob points to the R position, When the red and black pens collide, a few microamps of current are applied to the coil. When the coil is energized, it cuts the magnetic field lines and rotates like an electric motor, which can be pulled by the oil thread like a mosquito coil. It can only rotate and fix a 90 degree deviation angle. Mark the angle at which the watch needle operates, and various designs can be used to adjust the gear of a watch needle to measure various functions such as AC, DC, voltage, current, resistance, and transistor amplification.
2. Before measuring the meter head, it is necessary to calibrate the needle to zero. How to use it?
There is a 1.5V battery inside the meter, which cannot be used when it is out of charge or deviated from the positive and negative terminals due to a collision. Moreover, when measuring the resistance of each range, the meter needle must be zeroed on the R range. Short circuiting the red and black pen is necessary to have a circuit, and the pointer can only operate.
There is a fine adjustment on the meter, which can be adjusted at any time. The pointer calibration is not in place due to the voltage drop of 1.5V. Sometimes the battery may have poor contact, and during calibration, the pointer will return to the right end with zero deviation. At this point, it is necessary to adjust and fine adjust the deviation correction.
3. Why does the pointer return to the left zero position after measuring well? Because there is a "weighing weight" on the needle pendulum, when there is no electricity to push the pointer, this weight is pulled back by the pulling force of the oil wire. There is a deviation between the horizontal and vertical pointer zeroing of this meter head. You must check it before each use and do not use it if you have it. If it is not zeroed, the center is white ⭕ You can use your nails to rotate it.
