A device for converting angular displacement or linear displacement into electrical signals.

The former became encoder, the latter known yardstick. According to the readout encoder can be divided into two types: contact and non-contact. Contact the output brush, brush, a contact conductive region or insulating region to represent the status code is "1" or "0"; non contact type acceptance of the sensitive element is photosensitive element or a magnetic sensitive element, the photosensitive element to translucent and opaque area to represent the status code is "1" or "0".

According to the working principle of the encoder can be divided into two categories of incremental and absolute. Incremental encoder is to convert the displacement into a periodic signal, and then the electrical signal into a counting pulse, the number of pulses used to indicate the size of the displacement. Each position of the absolute encoder corresponds to a defined number code, so that its value is only related to the beginning and end of the measurement, but not in the middle of the measurement. Rotary incremental encoder to rotate the output pulse, through the counting device to know its location, when the encoder does not move or power outage, rely on counting the internal memory of the device to remember the location. In this way, when the power failure, the encoder can not have any movement, when the call work, the encoder output pulse process, there can be no interference and loss of pulse, or the zero point of the memory of the counting device will be offset, and the amount of this offset is not known, only the production of the wrong results appear to know.

The solution is to increase the reference point, the encoder passes through the reference point, the reference position to modify the memory location of the counting device. Before the reference point, it is not to ensure the accuracy of the location of the. Therefore, in the industrial control have each operation to find a reference point, boot change method.

For example, printer scanner positioning is the principle of incremental encoder, each boot, we can hear the pitter patter of a ring, it is looking for reference zero before work.

Incremental encoder features:

When the rotating shaft of the incremental encoder is rotated, the corresponding pulse output is realized, and the counting starting point of the rotating shaft is arbitrarily set. A shaft encoder ring will be a fixed output pulse, pulse number by the encoder grating line number. Need to improve the resolution, the use of 90 degree phase difference of the A, B two-way signal to double or replace the high resolution encoder.