Multimeter measuring resistance recalibrate zero after shifting
From the principle of measuring resistance with a multimeter, the multimeter uses the single-coil ohmmeter method to measure resistance, etc.
Since the resistance value connected to each resistance file is different, it increases by 10 times, such as ×1, × 10, × 100, × 1000, × 10k.
When the terminals are short-circuited, the internal resistance of the battery is connected in series with the internal resistance of the meter head and the resistance of the ×1 gear. When the battery voltage remains unchanged, the current flowing through the meter coil just corresponds to the ohmic zero position, which corresponds to zero. The terminal voltage of the head coil of the bit is fixed.
If the resistance value of each gear is changed, the terminal voltage of the meter will change, so that the current flowing through the meter will also change accordingly, and the needle will no longer point to the ohmic zero position.
For example, when the resistance level is changed from R × 1 level to high level one by one, the voltage of the meter head is also reduced one by one, and the current is reduced one by one, and the pointer deflection will not reach the ohmic zero position, which will cause a large measurement error.
Therefore, the zero adjustment knob must be adjusted so that the coil current of the meter remains unchanged, so that the pointer points to the ohmic zero position again to ensure the accuracy of each gear during measurement.
