Rockwell Automation 1746-HSCE2 Multi-Channel High Speed Counter Module - Manual (Page 45)

Publication 1746-UM002B-EN-P - August 2004
Installation and Wiring 3-5
• Shields should be grounded only at one end. Ground the shield
wire outside the module at the chassis mounting screw. Connect
the shield at the encoder end only if the housing is electronically
isolated from the motor and ground
.
Figure 3.3 Grounding the Shield Wire at the Chassis Mounting Screw
• If you have a junction in the cable, treat the shields as
conductors at all junctions. Do not ground them to the junction
box.
• If your application requires only low frequency inputs, you can
use a filter to minimize high frequency noise.
• If the Z pulse is edge aligned with A or B pulses, capture/preset
operation may be affected by ± 1 count. A small capacitor
(0.01µF) across the Z inputs will dis-align these inputs and
should correct this condition. See Z-pulse Preset Operation on
page 2-8.
Considerations for Reducing Noise
In high noise environments, the 1746-HSCE2 inputs may accept “false”
pulses, particularly when using low frequency input signals with
slowly sloping pulse edges. To minimize the effects of high frequency
noise on low frequency signals, the user can do the following:
• Identify and remove noise sources.
• Route 1746-HSCE2 input cabling away from noise sources.
• Install low pass filters on input signals. Filter values are
dependent on the application and can be determined
empirically.
• Use devices which output differential signals, like differential
encoders, to minimize the possibility that a noise source will
cause a false input.
Chassis Mounting Tab
Spade Connector
Mounting Screw
Star Washer