resolver vs. tach


Thread Starter

thomas allen

In a paper machine drive application, what are the advantages and disadvantages in using resolvers vs tachs?

Alan Rimmington

It depends what your plans are for the use of the rotary encoder (resolver ?) or tacho. The tacho will allow you to measure the speed, this will usually be in the form of an analogue signal, this is easy to use in a feed back loop to a drive control or other control system (the tacho may give direction by a minus value being reverse). The rotary encoder can give you more information such as speed, angle (position) direction. The encoded signal will require more processing ready for control but this can be easily achieved if the correct hardware is available. If all you require is to be able to set a speed and have some sort of loop control then the tacho is the way to go. However if you want to for instance turn the paper roll a set number of times, or a part turn etc etc then the rotary encoder is the way to go. [email protected]
hi, we have a machine which has 40 resolvers for feed back on deck positions and drive speeds on a flexo printing press. Tacho's are an analog device used for speed feedback to say a dc drive and can come with various resolutions(ie 0.06 volts per rev). A resolver on the other hand reports actual speed,direction and actual degrees from 0-360 and then actual position of the rotor is can be calculated. We control or decks to 1 micron which is pretty good. I haven't been able to work out if encoders are better or not but these are pretty rugged and stable with good resolution. If you want to know more email me and i'll try and help. [email protected] cheers lee