What is the relationship between absolute encoder accuracy and resolution?
The information comes from:the Internet posted on:2023-06-27
The number of bits of the single turn absolute value encoder represents the number of code tracks of the code disk. Because the binary code disk is used (the Gray code is the same), its precision becomes several powers of 2. For example, 12 bits is the 12th power of 2, which is 4096. The resolution and accuracy of the encoder are not necessarily equivalent, and the accuracy is determined by various factors such as reticle, mechanical concentricity of the encoder disk, reading response speed, temperature characteristics, etc. If an encoder achieves high resolution by subdividing the sine wave of a reticle, its accuracy does not improve, and subdividing only improves resolution. What is the accuracy of the line before subdivision and what is the accuracy after subdivision? Therefore, the accuracy of some high-resolution encoders depends on how many lines were used before subdivision. The current location data transmitted through SSI must consider the following "best case" and "worst case" scenarios.
The output of positional data depends on several parameters, such as factors, conversion time, data format, etc. Therefore, the processing time may vary. Using a processor system, you will only get an average response time. If you use the highest frequency of 500kHz to poll SSI channels. I.e. (pulse time 2 μ S * 26 bits+minimum required pause time of 40 microseconds) is the shortest time of approximately 100 μ S. Afterwards, the system will require an additional 400-500 μ S's time is used for data updates, so in the "worst case" scenario, you may get the same result (position value) three times! Only by using a much faster DSP or ASIC can you achieve shorter time (with a factor of 10), or use an encoder with SIN/COSINE code channels applied to motor control systems. This design is usually not too expensive (providing encoder types that reduce some requirements):
Incremental encoders with cable connectors, absolute encoders with cable connectors, and sealed enclosures (such as parallel single coil, SSI, or BiSS). If pulse per revolution (PPR) is selected correctly, it can simplify the calibration coefficient. Once the PPR is selected, or as long as it is calculated according to the formula in the technical manual. When selecting a calibration constant, remember to approach 1 as close as possible. The value of the calibration constant is the resolution of each pulse for your best encoder.