Incremental Encoder Resolution, Multiplication and Subdivision Technology

Incremental Encoder Resolution, Multiplication and Subdivision Technology

The incremental encoder code disk is made up of a very large number of grating lines, there are two photoeyes to read the A and B signals, the density of the lines determines the resolution of the incremental encoder, that is, the smallest change in angular value that can be read with resolution. The parameter representing the resolution of an incremental encoder is the PPR, or pulses per revolution.

Incremental encoder A/B output waveforms generally have two kinds, one is a steep rising edge and a steep falling edge of the square wave signal, a slow rise and fall, waveforms similar to sinusoidal Sin/Cos curve waveform signal output, A and B difference of 1/4T period 90 degrees phase, if A is a class of sinusoidal Sin curve, then B is a class of cosine Cos curve. For the square wave signal, A, B two phase difference of 90 degrees phase, so that, in the 0 degree phase angle, 90 degrees, 180 degrees, 270 degrees phase angle, the four positions of the rising and falling edges, so that, in fact, in the 1/4T square wave cycle can be angular changes in the judgment, so that 1/4 T cycle is the minimum measurement step, through the circuit for these rising and falling edges in the judgment, you can be 4 times the PPR reads the change of angle, which is the quadruple frequency of the square wave. This judgment can also be done with logic, 0 on behalf of the low, 1 on behalf of the high, A/B two-phase changes in a cycle is 00, 01, 11, 10. This judgment can not only be 4 times the frequency, but also to determine the direction of rotation.

Strictly speaking, the highest square wave can only do 4 times the frequency, although some people use the time difference method can be subdivided more finely, but that is basically not the incremental encoder recommended (recommended), the higher frequency to be used to incremental pulse signals are SIN/COS class of sine and cosine signals to do, the subsequent circuit can be read through the change in the phase of the waveform, the analog-to-digital converter circuit to be subdivided by 5, 10, 20, and even more than 100 times. After subdividing, it is then output as a square waveform. Encoder installation installed after the reduction gear, such as the shaft end of the winch rope reel or the last section of the reduction gear shaft end, this method has no gear back and forth clearance, the measurement is more direct, higher precision, this method is generally measured over long distances, such as a variety of lifting equipment, feeding trolley positioning.

The multiplier of frequency division is actually limited, first of all, the analog-to-digital conversion has the problem of time response, the speed of analog-to-digital conversion and the resolution of the accuracy (precision) is a pair of contradictions, it is not possible to infinitely subdivided, subdivided into too fine, the response and the accuracy is problematic; Secondly, the original encoder's precision of engraved lines (accuracy), the output of the class of sine and cosine signals are limited in their consistency, the perfect waveform, the subdivided into too fine, it will only expose the deviation of the original code disk more obvious and bring about errors. The deviation of the code disk is exposed more obviously, and bring errors. Subdivision is easy to do, but to do a good job is very difficult, on the one hand, it depends on the original code disk scribing accuracy and output waveform perfection, on the other hand, it depends on the response speed of the subdivision circuit and resolution accuracy. For example, the German industrial encoder, the best recommended subdivision is 20 times, higher subdivision is its recommended higher precision angle encoder, but the speed of rotation is very low.

An incremental encoder subdivided output A/B/Z square wave, but also can again 4 times the frequency, but please note (attention), subdivided for the encoder's rotational speed is required, generally lower. Absolute encoder is widely used in water conservancy, light industry, machinery, metallurgy, textile, petroleum, aviation, navigation and other industries. Specific to the project category such as: rotary table, gate opening, valve opening, hoist crane positioning, traveling crane positioning, level measurement, missile launch angle positioning, missile air rudder measurement, electronic latitude and longitude and other high-precision measurement and positioning occasions. Binary encoder binary is composed of two numbers, 1 and 0, which can represent two states, i.e. on and off. All any information entered into the computer is eventually converted into binary. ASCII is currently the universal code. The most basic unit is bit. in addition, such as the original code disk engraving accuracy (precision) is not high, the waveform is not perfect, or subdivision circuit itself is limited, subdivision maybe waveform serious distortion, the size of the step, lost step, etc., the selection and use of the need to pay attention.