Zero adjust knob in a analog meter?

The zero adjust knob on an analog meter is used to calibrate the meter's needle to the zero position when no measurement is being taken. This ensures accuracy by eliminating any offset that might be present due to manufacturing variances or environmental factors. By turning the knob, the user can align the needle with the zero mark on the scale, allowing for precise readings during measurements. It's an essential feature for maintaining the reliability of the meter's measurements.