Basic parameters of the encoder

Resolution: It refers to the smallest unit that an encoder can distinguish. For incremental encoders, their resolution is expressed as the number of pulses generated when the encoder's rotating shaft rotates one full circle, that is, Pulse Per Revolution (or PPR). The number of light-transmitting line slots on the code disk is actually equal to the resolution, also known as the number of lines. The more common ones range from 5 to 6000 lines, meaning that the motor can output 5 to 6000 pulses in one revolution. If the motor is equipped with a reducer with an n speed ratio, the number of pulses output by the motor in one revolution is n times the number of lines of the encoder. For example, if the encoder has 11 lines, If the motor is equipped with a reducer with a 270-speed ratio, the encoder will output 11*270=2970 pulses for each revolution of the reducer's output shaft. For absolute encoders, the number of bits used in the internal code disk is its resolution, with the unit being bits (bit), which is further divided into single-turn resolution and multi-turn resolution.

Precision: First of all, it should be made clear that precision and resolution are two different concepts. Accuracy refers to the maximum error between each reading of the encoder and the actual position of the rotating shaft, which is usually expressed in angles, angular minutes or angular seconds. For instance, some absolute encoders' parameter tables may state ±20 ", which indicates that there is an error of ±20 arcseconds between the encoder's output reading and the actual position of the rotating shaft. The accuracy is jointly determined by various factors such as the processing accuracy of the code disk marking lines, the concentricity of the rotating shaft, the temperature characteristics of the material, and the response time of the circuit.

Maximum response frequency: It refers to the maximum number of pulses output by the encoder per second, with the unit being Hz. Calculation formula: Maximum response frequency = Resolution * Shaft speed /60.

Signal output form: For incremental encoders, the signal of each channel is independently output. The output circuit forms usually include collector open circuit output, push-pull output, differential output, etc. For absolute encoders, since they directly output tens of binary digits, to ensure transmission rate and signal quality, serial output or bus output is generally adopted, such as Synchronous Serial Interface (SSI), RS485, CANopen or EtherCAT, etc. There are also some that use parallel output The output circuit form is the same as that of the incremental encoder.

Maximum rotational speed: It refers to the highest rotational speed that the encoder mechanical system can withstand.