incremental rotary encoder
incremental rotary encoder
(OP)
hello..
any one could give me the actual application and difference of incremental and absolute rotary encoder?
i had encounter a steel rolling machine which uses as what they say an incremental encoder.., the machine now was inoperational due to it was on the alarm display:check machine rotary encoder.
anyone could give me some basic procedures, perhaps a standard procedures to test or diagnose the rotary encoder from defects and abnormalities?
my colleague test the output pulses of the unit, phase a, phase b, phase z and phase a', b' as well..but i doubt that while stall(not in motion)we got pulses on phases..does it mean that the encoder is not defective?
by the way, the unit is rated on 5 voltdc, 500 pulse where the ouput is conected to a control cards..not in PLC.
thanks..
any one could give me the actual application and difference of incremental and absolute rotary encoder?
i had encounter a steel rolling machine which uses as what they say an incremental encoder.., the machine now was inoperational due to it was on the alarm display:check machine rotary encoder.
anyone could give me some basic procedures, perhaps a standard procedures to test or diagnose the rotary encoder from defects and abnormalities?
my colleague test the output pulses of the unit, phase a, phase b, phase z and phase a', b' as well..but i doubt that while stall(not in motion)we got pulses on phases..does it mean that the encoder is not defective?
by the way, the unit is rated on 5 voltdc, 500 pulse where the ouput is conected to a control cards..not in PLC.
thanks..





RE: incremental rotary encoder
RE: incremental rotary encoder
An absolute encoder has multiple connections to it, power, common and enough lines to give you a set of outputs. Each output is unique, it is really a part of a data set. 4 lines could give you a hex out of 16 cominations, 0-15. The more lines out the more resolution. The advantage of this is the absolute encoder, always gives a unique set of data. So if the system is off when the encoder is moved, once power is reapplied, the system can still read the unique value of where the encoder is, by the data word output.
Now, it sounds as if your system only needs speed feedback, so an incremental encoder is used (i.e. you don't need all the additional position info). The phasing of A-B tells direction and the rate of the pulses being output sets the speed.
You can get a rough test with a good digital meter which reads dc volts and hertz. At standstill read A to A Not, B to B not. One should read high, one should read low. Keep the comm lead of the meter on the respective Not phase. You can also read from tach Common to A, Anot, B, Bnot. Look at the good tach to get the values you should see. Now put the meter in Hertz mode and read A-Anot, B-Bnot. The hertz should be the same on both phases. Then try phase A to comm, Anot to comm, B to comm and B not to comm. The Frequency should be the same on all.
I assume you have a drive on this, so if it is a modern DC drive, put the feedback in Arm Volts mode so you can turn the motor slowly while you do the hertz test. If it is an AC drive, hopefully it will allow you to switch from closed loop vector to either open loop vector or volt/hz.
Running the drive in one of these other modes also lets you check out the encoder with a scope, which is a much better way of finding what the encoder is doing.
Good luck.
RE: incremental rotary encoder
http://www.beiied.com/encoder_products_descr.html
for differences between incremental and absolute encoders in terms of their parameters
RE: incremental rotary encoder
http://www.mitchell-electronics.com/TI5order.html
etc. for encoder cable and motion control diagnostic tools
RE: incremental rotary encoder
Both contain basic information about different encoder types.
RE: incremental rotary encoder
i got your point RADARRY!!
god bless!!
RE: incremental rotary encoder
I am using a 1000 ppr incremental encoder mounted on to 1440 RPM 4 pole vertical mounting induction motor. The shafts are coupled using a flexible coupling. The encoder signals are connected an A-B PowerFlex 700 AC Drive. The encoder takes a 4.75 V to 30 V DC input. The A, B and Z signals of the encoder are connected to corresponding terminals on the drive. At low RPMs, say 150 RPM, the encoder speed parameter of the drive frequently drops to 2 - 3 RPM and then returns back to 150 RPM. This happens intermittently and the duration of this hardly for a second. On checking the counts parameter of the drive, it too suddenly goes to as low as 1. However the frequency of this problem reduces drastically as the speed of the motor is increased.
Can anyone suggest the possible cause and solution for this problem.
Thanks and regards,
Mathew
RE: incremental rotary encoder
RE: incremental rotary encoder
B=--____----____--
So both may be high or low or only one of them -- all 4
combination happens to have the same probability.
Coupler intenmittent problems usually are caused by
incorrect levels ( overload, etc.) or lack of bebouncing.
<nbucska@pcperipherals.com>
RE: incremental rotary encoder