text: <s>[INST] PF755 master/follower application - recommended encoder Summary: single channel / single ended or dual channel / differentialHi, I have an application in which I am hoping to use two PowerFlex 755 AC drives in a Master / Slave relationship in a roll-to-roll web handling application. My plan is to equip the master drive with a 20-750-ENC-1 single incremental encoder module and to equip my slave drive with a 20-750-DENC-1 dual incremental encoder module. I will have an encoder mounted on both the master motor and on the slave motor. I plan to wire the master encoder to both the master drive (as feedback for the controlled master motor) and to the slave drive (as an external reference). I will wire the slave encoder to the slave drive (as feedback for the controlled slave motor). I am hoping to use the electronic gearing feature to ensure that I can run the slave motor at a fixed ratio of the master motor. Ideally, I am hoping that I can achieve good performance (in terms of accurate speed control without motor cogging) within a 100:1 speed range (motor RPM ranging from 18 - 1800 rpm). With this in mind, I am planning to use a high quality vector duty motor. My application is basically a constant speed application, where the master roll and the slave roll are used to convey a continuous web material through a machine. The speed ratio is nominally always 1:1 because if the rolls do not turn at the same speed, it would either create slack between the two rolls or break the web. This being said, I do need the flexibility to adjust this ratio between approximately 0.998:1 and 1.002:1 to compensate for stretching or shrinking of the web material in a dryer that it passes through. I *think* there is a good chance I would be able to get the performance I want with independent drives (not using electronic gearing) by just entering set points in the desired ratio, using the same acceleration/deceleration settings for both drives, and making sure I issue start and stop commands for both drives at the same time. The reason I'd like to try the electronic gearing feature is because I think it might help me do a better job of coordinating the speeds of the drives during acceleration and deceleration. I figure if it turns out not to be unnecessary, I will only have wasted the extra cost of one dual-encoder module and hopefully I will have learned something about the electronic gearing feature that might help in future, more challenging applications. My question for today is, will single-ended, single-channel encoders of appropriate resolution be sufficient for achieving good speed control? Or will there be some advantage to be gained if I consider using dual-channel, differential encoders? Any advice or suggestions will be greatly appreciated. Thanks and best regards, Paul [/INST] Consider using an encoder splitter on the master encoder signal - master encoder goes into the splitter; output1 goes to the master drive, output 2 goes to the follower drive. https://www.motrona.com/en/products/signal-converters/level-converters-signal-splitters/gv210-pulse-switch-distributor-and-splitter-for-incremental-encoder-signals.html I think I'd go with differential encoders myself. In all other respects, you've got it wrapped up pretty well. \\n </s>