David is correct there is an index marker output from the heads 9100/9410 and USDigital encoders. ?Even the old versions?
It¡¯s pin ¡°I¡±. ?I was playing with it to count motor revolution speed. ?Part of testing the Gemini electronics I do when repairing them
i have to ensure sidereal rate is in actual fact ¡°sidereal rate¡± and using this pin to count period is an easy method. ?In reality I went s different method I used motor pinion chopper disc snd opto coupler. ?The motors jitter and I can program to time it over a number of revolutions to get a better picture of accuracy¡¡This way I can test other motors etc¡but, that¡¯s just my method FWIW
David is spot on. ?The index is useful information especially wrt PEC. ? ? Well kinda. ? Would be better to have an encoder on the worm. ?
I guess the philosophy is to keep it simple and cheap as you can. ?Adding a worm index has benefits and costs and maintenance or user setup issues. My guess is why do all this if the system is already accurate enough in counting pulses throw in worm index will need done error recognition/correction?
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Brendan
