What is a Return Gap?

The return error refers to the absolute value of the difference between the displayed value of the measuring instrument in the same direction, the measured value does not change, and the measuring instrument travels in different directions. Also called hysteresis error. When the measuring instrument performs the forward and reverse measurement on the same size, due to structural reasons, the indicated values cannot be exactly the same. This error is called the return error.

The return error refers to the absolute value of the difference between the displayed value of the measuring instrument under the same conditions, the measured value does not change, and the measuring instrument travels in different directions. Also called

In JJF1001 "General Measurement Terms and Definitions", there is no term "backhaul error", but another term "dead zone" is defined in 7.13 to describe-"the maximum two-way change in the incentive that does not cause the measurement instrument to respond to changes Interval ". Therefore, the return error is an indicator for measuring the response characteristics of the equipment " ^[2]

Take the motor forward and reverse as an example, back and forth once,

The motor itself does not have a return error, how much the encoder reads, how many pulses the stepper motor rotates, and the servo system is usually more accurate than the stepper motor. The return error is caused by a transmission mechanism such as a screw connected to the motor output shaft. Therefore, the servo system can precisely control the motor and cannot handle the return error.

Therefore, in addition to powering up the incremental encoder to seek zero, the zero-position switch can also return to zero during the movement for high-precision movements to eliminate return errors. Even if the absolute encoder does not need to be powered to find zero, the photoelectric switch can also be used to eliminate the return error. When it is necessary to ensure that there is no return error in both directions, it is necessary to set zero switches at both ends so that the motor will first align with the zero position in this direction after changing direction, and then use this as the zero position to measure the movement displacement ^[2] .