How to connect screened cable?

connecting screened cables

I have a motor system with optical encoder. I have two boards. One is control board and the other is power board. These boards are connected via a flat cable which is 20-25cm. Without encoder is in operation, everything seems ok. But when it's in operation, output to the motor is affected. This happens even if i completely isolate the encoder. Then i'm suspicous that encoder pulses affect this 20-25 cm long cable from the air. I'll reduce this cable as possible as i can. But before that, i'm planning to use screened cable both for encoder connection and the cable between the boards. What i wonder is how will i connect this screened cable or how will i connect it to ground? Which ground should i connect it and which side of it? If any other suggestions about this problem i'll appreciate it also. Thanks.

Try to do the following:

- run shielded wires from rotary encoder in twisted pairs to limit straight line antenna effects ..

- ground signal common wiring at one point and, if possible, float this ground from Earth ..

- connect all shields to Earth (PE) at one end to drain the induced voltages ..

Regards,
IanP

When i connect the ground to earth, it worsened the situation. When i connect the cables screen to its own ground. It made a little better. I couldn't solve the problem and it made me mad. I want a world without noise