Principle characteristics of various rotary encoders2021

Rotary encoder is a measuring device, a speed displacement sensor that integrates opto-mechanical technology. It can be used to measure distance, displacement, angle, speed, and a common electronic component in the field of industrial control. Today, we will introduce various types of rotary encoders. The principle and characteristics of the device.

Principle characteristics of incremental rotary encoder

When the incremental encoder shaft rotates, there is a corresponding phase output. The determination of the direction of rotation and the increase or decrease of the number of pulses need to be realized with the aid of the direction circuit and counter at the rear. The starting point of counting can be set arbitrarily, and unlimited accumulation and measurement of multiple turns can be realized. It is also possible to use the Z signal for each pulse transmitted as a reference mechanical zero position. When the pulse has been fixed and the resolution needs to be improved, two signals with a phase difference of 90 degrees A and B can be used to double the frequency of the original pulse number.

Principle characteristics of absolute rotary encoder

In the case of the absolute encoder shaft rotator, there is a code (binary, BCD code, etc.) output corresponding to the position one-to-one, and the positive and negative direction and the position of the displacement can be determined from the change of the code size, without the need to determine the circuit. It has an absolute zero code. When the power is cut off or turned off and then turned on and re-measured, the code of the power cut or shut down position can still be read accurately, and the zero code can be found accurately. Under normal circumstances, the measuring range of the absolute value encoder is 0-360 degrees, but special models can also achieve multi-turn measurement.

Principle characteristics of sine wave encoder

Sine wave encoders are also incremental encoders. The main difference is that the output signal is a sine wave analog signal instead of a digital signal. Its appearance is mainly to meet the needs of the electrical field-as the feedback detection element of the motor. On the basis of comparing with other systems, people can use this kind of encoder when people need to improve the dynamic characteristics.

In order to ensure good motor control performance, the feedback signal of the encoder must be able to provide a large number of pulses, especially when the speed is very low, the use of traditional incremental encoders to generate a large number of pulses, there are problems in many aspects When the motor rotates at a high speed (6000rpm), it is difficult to transmit and process digital signals.

In this case, the bandwidth required to process the signal to the servo motor (for example, the pulse per revolution of the encoder is 10000) will easily exceed the MHz threshold; on the other hand, the use of analog signals greatly reduces the above-mentioned troubles and has the ability to simulate A large number of pulses from the encoder. This is thanks to the interpolation method of sine and cosine signals, which provides a calculation method for the rotation angle. This method can obtain a high-fold increase of the basic sine, for example, from 1024 sine wave encoders per revolution, more than 1000,000 pulses per revolution can be obtained. The bandwidth required to receive this signal is sufficient as long as it is slightly larger than 100KHz. The interpolation frequency multiplication needs to be completed by the secondary system.