Rockwell Automation System Design for the Control of Electrical Noise - Manual (Page 51)

Publication GMC-RM001A-EN-P — July 2001
Filtering Noise 5-5
Ultrasonic Transducers Ultrasonic transducers often induce high noise levels onto their DC
supply and signal lines. To reduce noise using ultrasonic transducers:
1. Mount two DC filters close to the device with ferrite sleeves
between the capacitors and the sensor.
2. Feed the DC power supply through one sleeve.
3. Bring out the analog signal via the other sleeve.
Note: Use shielded cable for the analog signal.
The filter ground should be close coupled to the machine metalwork
close to the sensor.
Xenon Flashing Beacons
(strobe lights) Strobe lights can generate high voltage transients on their 24V dc
supply lines. To reduce this source of noise, try using one of these
two alternatives.
• Mount a DC filter close to the lamp (ferrite sleeve on the lamp
side) with its common attached to chassis ground.
• Use shielded cable between lamp and control panel, with DC filter
at the point where the cable leaves the panel.
AC Line Filters AC line filters contain capacitors connected between phase and the
filter chassis. Line voltage is with respect to ground. The capacitor
allows a small but potentially dangerous amount of current to flow to
ground.
ATTENTION
!
To avoid personal injury and/or damage to
equipment, ensure AC line filter capacitors are
properly connected to safety (PE) ground.