Precautions for the selection of absolute encoders

Incremental encoders.

It encodes the difference between the two values before and after the sampling value (not the absolute value). Absolute encoders, on the other hand, encode absolute values (not relative values). For example, x[1]=2, x[2]=9

The incremental encoder encodes 9-1=8 to get 1000Absolute encoders get 0010 and 1001

2.When using incremental encoding, the transmission rate must be high enough to otherwise produce distortion, like lazy distortion in capacitive filtering.

There is no special requirement for the transmission rate when encoding absolutely, and the speed is slow and not distorted, as long as you can tolerate it.

1. What is an incremental encoder 2. The concept of an absolute encoder 3. The difference between the two.

The incremental encoder is a pole pair of one turn (column) and absolutely a pole pair of two turns (2 or 3 rows), and the absolute measurement of the single-turn position is achieved by the nonius principle of vernier calipers.

Absolute encoders use natural binary or cyclic binary (Glee's code) for photoelectric conversion. The difference between an absolute encoder and an incremental encoder is that there is a line pattern on the disc that transmits light and does not transmit light, and the absolute encoder can have a number of codes, and the absolute position is detected according to the code on the readout disc.

Absolute-value encoder: the code is determined by the mechanical position, it does not need to memorize, does not need to find a reference point, and does not need to count all the time, when and wait to know the position, when to read the position.

Among them, the number of raw pulses of the output is not directional, and the direction needs to be judged and counted by the electronic circuit in the encoder chip, and the final output positive and negative values are used to represent the direction of rotation and the magnitude of the angle.

The absolute value of the encoder conforms to the Profibus protocol, and the operation is based on the Class 1 and Class 2 pair of jujube wheels compared to the Class 1 based encoder, the position value and the diagnostic data, byte1....16 available.

If you want to measure rotations beyond a 360-degree range, you need a multiturn absolute encoder. Encoder manufacturers are looking for Shanghai Kaidi electronic encoder selection.

The working mode is different: the incremental encoder needs to return to the origin after power-off, it cannot output the absolute position information of the shaft rotation, there is a zero-point cumulative error, the anti-interference is poor, the shutdown of the receiving equipment needs to be power-off memory, and the start-up should be given to the zero or reference bit.

Refers to the type of encoder with different increments: it converts the displacement into a periodic electrical signal, and then converts the electrical signal into a counting pulse, and the number of pulses indicates the size of the displacement.

And multi-turn can keep n lap not repeated, depending on the choice, the principle is similar to the principle of clock gear machinery, of course, there are also electronic rings, Japanese absolute encoder products are the majority.

Problems of incremental encoders: incremental encoders have problems such as zero cumulative error, poor anti-interference, power-off memory when receiving equipment is shut down, and zero balance or reference position should be found when booting up, which can be solved by using absolute encoders.

Incremental Rotary Encoders and Absolute Rotary Encoders Incremental rotary encoders provide a certain number of pulses per revolution of the shaft. Periodic measurements or pulse counts per unit of time can be used to measure the speed of movement.

The specific differences are as follows: the working mode is different: the incremental encoder needs to return to the origin after power-off, it cannot output the absolute position information of the shaft rotation, there is a zero-point accumulation of rent and punch meter error, the anti-interference is poor, the shutdown of the receiving equipment needs to be remembered by power-off, and the start-up should be given change or reference bit.

First, the nature is different.

1. Incremental encoder: the displacement is converted into a periodic electrical signal, and then the electrical signal is converted into a counting pulse, and the number of pulses is used to express the size of the displacement.

2. Absolute encoder: because every position is absolutely unique.

1. Anti-interference, no need for power-off memory, has been more and more widely used in a variety of industrial shouting and positioning control systems.

Second, the principle is different.

1. Incremental encoder: There is a gap at equal angles (divided into transparent and opaque parts) on the edge of a code disc, and the light source and image sensor are installed on both sides of the encoder. As the disc rotates with the working axis, the light and shadow change with each slot rotated.

After shaping the stool, the output signal of the electric pulse of a certain amplitude and power can be obtained, and the number of pulses is equal to the number of rotating slots. The pulse signal is sent to a counter for counting, and the angle of rotation of the disc can be known from the measured number.

2. Absolute encoder: Absolute encoder because of its high precision, the number of output bits is more, if the parallel output is still used, each output signal must ensure a good connection, for more complex conditions isolation, cable cores more, which brings a lot of inconvenience and reduces reliability.

Therefore, absolute encoders are available in multiple digits. The output type, generally choose serial output or bus type output, German absolute encoder serial output is the most commonly used SSI (synchronous serial output).

1 All absolute encoders are unique in each position (i.e., absolute) and are different from incremental encoders. The position of the incremental encoder is determined by the accumulation of counting pulses of the in-situ reference, and the reading state should always be continuous, uninterrupted, and the anti-interference ability is poor, which is mainly used for short-term relative displacement or speed measurement; Absolute encoders are based on an instantaneous readout data code system to build up information, no two positions are the same.

The signal read out by the absolute encoder can be a digital signal such as natural binary or Gray code, and the probability of error code in its Gray code is small, and for the operation of the rear secondary instrument, because it is a digital calculation, it is not easy to increase its error, therefore, the reliability of the data transmitted and calculated is high.

Absolute encoders are classified according to the principle of encoders, including absolute encoders and incremental encoders; The bus encoder is an output form (output signal) of the encoder - Dingxi Zhao