Servo Noise Problem

[Dramesh_babu 0]

Hi, I am using Mitsubishi MRJ2S Servo System with FX2N 48MR+8AD in one of my project. Whenever I switch on servo signal,a Linear Displacement sensor (connected to 8AD module) value fluctuates.The Displacement sensor has 0-10v O/p with stroke length of 25mm. we gone through Mitsuhishi servo manual fully & wired Servo amplifier & servo Motor with proper arrangements(like earthing).But still because of noise created by servo motor,my other equipments value totally varies.Can anyone guide me ?

[WKla 0]

Maybe is because you are not using the average data from the AD module. BFM#2 to BFM#9 represents the number of times of averaging for each channel. The instruction is: TO K0 K2 H200 K1 H200 represents the number of times of averaging for channel 1.

[TimWilborne 108]

How much is the value fluctuating? Are you sure it is not the servo oscillating?

[panic mode 246]

post more details on how is it connected right now, what are the cable lengths, how are they routed, is sensor wiring spliced anywhere (connector, terminals) or shared (like shared sensor power from some field junction box etc.), is the shielding compromised? how much are shields stripped back (what is the length of wires not protected by shield). if you have more than 2" or 5cm of shield removed anywhere, you are asking for trouble (one of the guys who worked here for short time couldn't figure out why is his encoder position was drifting over time, he had encoder cable wired temporarily only and shield was stripped about 15", big VFD drive was only 4-5" away from this). note that if you are splicing analogs on terminal strip, terminals are not shielded either. i wouldn't want to start with averaging and filtering, i would first verify that everything is already done to maintain integrity of the signal, then it's easy to distort and delay information... first you have to verify that both analog input and servo wiring are per drawings in manual: - use shielded cables for all signal cables as well as motor power - any such signal including this analog input to be grounded in one place only - noisy power lines (such as servo motor cable) can be grounded in more than one place. - run signal cables away from power cables (and PLC away from servo drive) - make sure your grounding is proper (use proper short and fat copper grounding bar and have all grounds connected in same place, do NOT use bunch of terminals and jumpers) - if your sensor is 3-wire device, make sure that return (0VDC) is wired correctly (never shared with other I/O, goes from sensor to analog card - period, you may use connectors, terminals etc. but do not branch of to something else)

[Dramesh_babu 0]

Hai ,Thanks for the all the people reponse.I used seperate Isolated Power supply for my analog input source.Now the signal fluctuations have much more improved.Thanks to all.

[panic mode 246]

thanks for feedback. you say fluctuations reduced, but by how much? what is the fluctuation amount right now? fraction of percent or something bigger? is it still acceptable? maybe it wasn't servo related at all (just dirty 24V power...).

[TimWilborne 108]

Or mainly, as Panic Mode stessed before, how was/is the shielding?