The output value (indicated value) when the instrument input value is at the starting point of the range (no flow, zero flow) is called the instrument (flowmeter) zero point;

The phenomenon of output change caused by internal and external factors such as temperature when the input is constant is called drift, and the phenomenon of output change when the input is constant is called zero drift.

When the input is unchanged at zero, the phenomenon that the indication (output) is not at the beginning of the output range is zero offset.