Background knowledge
RLS has a good background on different types of encoder which is explained really well. Not worth writing about here because they do such a good job
...
The page on resolution, accuracy and repeatability are particularly important to understand, as these can be the least intuitive to understand (notes below in terms section):
https://www.rls.si/eng/encoder-handbook/resolution-accuracy-repeatability
Terms
Resolution: The smallest movement detected by the encoder
- Measured differently for linear and rotary encoders
Resolution - Linear (μm): The length of one measured step
Resolution - Absolute Rotary: The number of measured segments/units per revolution
- Ex. 13-bit = 213 = 8,192 steps per rotation
Resolution - Incremental Rotary: Pulses per revolution (PPR) is a signal pulse from one rising edge to the next and Counts per revolution (CPR) marks both rising and falling edges on both channels. You can get the CPR by multiplying the PPR by 4.
Accuracy: how close the output is to where it is suppose to be (where the encoder is saying it should be). It is the max measurement error.
- High resolution does not necessarily mean high accuracy
Repeatability: The max difference between different measurements at the same position.
- Even if all the measurements are wrong, if they are all wrong in the same way (so they are in a similar place at every revolution) it is repeatable.
Type
It has been decided by the other sub-teams to go with absolute rotary encoders for the sake of narrowing the scope of the first revision. In future revisions it might be worth considering to use incremental encoders in addition to the absolute rotary encoders.
...
If we are sponsored with free sensors we me as well used the best ones available.
Simple Trig & the Tolerance Stackup
...