The rotary encoder is an important mechanical position in the industry, Angle, length, speed feedback and participate in the control of the sensor, rotary encoder is divided into incremental value encoder, absolute value encoder, absolute multi-turn encoder.

Tell from external receiving devices (e.g., servo controller, PLC), the incremental value refers to A kind of relative location information of change, change from point A to point B signal of increase and decrease of calculation, also known as the "relative value", it requires continuous follow-up equipment count, because each time the data is not independent, but relies on the front of reading, on the previous data with power and interference produced by the error could not judge, causing the cumulative error; And the work pattern of "absolute" refers to the equipment after the initialization, determine a origin, after the position information of all is the absolute position and the "origin", it does not need further device of uninterrupted count, but directly read value, the current position for error caused power outages and interference, since each reading are independent is not affected by the previous, so as to not cause accumulated error, this is called "absolute type" working mode of receiving equipment.

For absolute value encoder within the definition of "absolute", refers to the inside of the encoder all location value, after the encoder production factory, all position is within range of "absolute" to determine within the encoder, after the initial origin, each location independence and uniqueness, its internal and external data refresh every time reading, don't rely on the previous data read, whether internal encoder or encoder outside, there should be no "count" and the previous reading of accumulative calculation, because the data is not "independent" "the one" "range all position has been definitely established in advance". It doesn't fit the meaning of the word "absolutely."

Therefore, the definition of a true absolute encoder refers to the absolute correspondence between all positions in the range in advance and the origin position, independent and unique absolute encoding independent of the internal and external count accumulation.

"Intentional confusion" and misunderstanding about the concept of "absolute" encoder

About absolute encoder, a lot of people know or stay on the position of the "blackout" save this concept, this is partial and limited, "absolute encoder is not only the problem of power outage, for receiving equipment, the real meaning of" absolute "is its data refresh and read in the encoder with both internal and external, independence, and uniqueness of every position, does not depend on the previous readings of" absolute code ", the definition of the "absolute" market or ambiguous, for some businesses will be for the concept of "obfuscation" :

Confusion 1: the "absolute operating mode" of the receiving device is confused with the "absolute" of the absolute encoder. Receiving device of the "absolute" refers to receiving device without counting uninterrupted accumulation, all locations for the origin of the equipment "absolute" work mode, in fact this model by incremental encoder + progressive counting device + battery memory itself, as can provide equipment "absolute" location information, it with absolute value encoder "absolute coding" is not a concept, it exists the counting error and the possibility of accumulative error count, counting device power supply failure probability and high speed can't response, etc.

Confusion 2: Confusion of absolute value single turn encoder + internal and external counting accumulator with true absolute value true multi-turn encoder. Absolute value lap + meter circle counting device, it is within 360 degree of absolute value, but after more than 360 degrees, its location, it is not "independent" "the one", it is to rely on internal or external to the count to determine how many circles lap absolute position information, the internal or external "counting device", and the nature of the incremental encoder + counting device + battery memory is the same, any error count, or counting assembly work when the power of instantaneous fault, can cause the error and accumulated to judgment, absolutely fraudulent false information. The true absolute multi-turn encoder, in addition to the position within 360 degrees is absolutely unique, the absolute code disk that continues to be driven by the gear machinery after 360 degrees still provides "independent" and "unique" absolute code that does not depend on the previous data refresh read accumulation. From the definition of "absolute", actually in front of the single ring absolute counting + accumulation device "false circle" absolute encoder, it cannot be called "absolute encoder circle", although within 360 degrees is absolute, but the work range of more than 360 degrees, it is no longer the only "absolute coding".

As for why the definition of "absolute" concept of the absolute value encoder should be emphasized, its significance is as follows:

First, you can provide an absolute code value for each axis position. Especially in the position control, the absolute value encoder can achieve direct internal high-speed reading and external output without counting, which is the "high speed" and "economic" characteristics of the absolute value encoder. It can reduce the calculation task of the subsequent receiving device controller, and reduce the cost of other additional input components. For example, industrial robots working in parallel on multiple axes can realize high-speed parallel and synchronous work on multiple axes. And a variety of control areas that require multi-axis synchronization.

Second, the absolute value encoder without counting does not need to refer to the drive after the power supply starts up or the internal or external power supply fails. The current accurate position can be obtained after the power supply is normal. In the case of complex interference in various industrial electrical environments (such as the interference of frequency converter and motor), the original position information of the absolute value encoder is absolute and will not be affected by the interference. The above characteristics, determine the safety and reliability of the encoder characteristics, can be used in occasions with security requirements, such as wind power propeller system, port machinery synchronization in positioning, lifting machinery, construction machinery, tower crane, elevator, engineering machinery, steel, metallurgy, petrochemical industry, water conservancy, electric power, medical equipment, solar tracking radar gun rotary device turning device, etc., as well as the heavy industry, nuclear industry, automobile manufacturing and other fields of large industrial robot.

Third, in today, fast and reliable digital data transmission is one of the core elements of absolute encoder, industrial standard of Canopen, profibus-dp fieldbus, Profinet, Eerthnet industrial Ethernet, Endat2.2, Hiperface, Biss, dedicated high-speed contains CRC data safe RS485 servo robots, such as special high speed data transmission protocol, the original "pulse" way to send information of incremental encoder could not be achieved. This is the high speed bus characteristic of the absolute value encoder.

Fourth, the characteristics of high resolution, the absolute value encoder to internal and external counting and output digital signals directly, so no longer subject to read the "pulse" and "accumulation" in the high speed of response speed to keep up with confusion, a mixture of advanced digital and analog technology, absolute encoder has been able to achieve high resolution, such as Germany's absolute value encoder single lap 25 (25 of 360 degrees within 2 square division), the high resolution can be content with the robot servo motor with high speed precise positioning and minimum interval jitter. For example, the precise calculation of the derivative of the position of acceleration and acceleration (motion rigidity), and the accurate positioning of the minimum slop of the front end of the robot arm, etc.

Integrated the above definition of "absolute" absolute encoder, in has characteristics such as high speed, security, applications request, must not use that confuse the meaning of "absolute encoder" or "false absolute encoder circle", and must be used in the true sense of the absolute value encoder or absolute value encoder, so many circle and any does not depend on the count (whether internal or external, there is no battery), the location of all independent, the only, absolutely, to ensure that the data is absolutely reliable and high accuracy.

When choosing and using the absolute encoder, please make sure whether it is the "absolute code" as described above, so as to ensure the absolute utility.