Checking For Ground Loops; Noise Suppression Devices Available - Watlow 945 Series User Manual

Wiring Guide
Table 4 -
Noise Suppression
Device Ratings
30
WATLOW Series 945 User's Manual
• "Islatrols" and other similar power line filters are designed to carry the power for
the control circuit and "buffer" the control circuit from A.C. line noise. Devices
like the Islatrol use media (electromagnetic filtering) other than electric circuits to
filter out electrical noise. Take care in matching the power capabilities of the filter
with power demands of the circuit. Keep line filters as close to the control as
possible to minimize the area for interference pick up.
• Islatrols are available from:
I - 101 (1A, 120VAC)
I - 202 (2.5A, 208/240VAC)
• The ultimate protection is an "uninterruptable" power supply. This "senses" the
A.C. power line; when the line fluctuates, a battery powered 60Hz inverted circuit
takes over, supplying power within one-half to one cycle of the A.C. line; very
expensive.

Checking for Ground Loops

To check for ground loops, disconnect the ground wire at the ground termination.
Measure the resistance from the wire to the point where it was connected. The
ohmmeter should read a high ohm value. If you have a low ohm value across this
gap, there is at least one ground loop present in your system.
Or check for continuity; your reading should be "open." If you do find continuity,
begin looking for the ground loops. Begin disconnecting ground in the system one
at a time, checking for continuity after each disconnection. When continuity reads
"open" you have eliminated the ground loop(s). Also, as you reconnect grounds,
keep making the continuity test. It is possible to reconnect a ground loop.
Noise Suppression Devices Available From Watlow
Watlow Controls stocks a few key noise suppression parts. You may order these
by calling your local Watlow distributor.
Item
Common Mode Line Filter
Differential Mode Line Filter
Metal Oxide Varistor
MOV
MOV
MOV
Quencharc
Control Concepts Corporation
328 Water Street
P.O. Box 1380
Binghamton, NY 13902-1380
Phone: 607/724-2484
I - 105 (5A, 120VAC)
I - 207 (7.5A, 208/240VAC)
Electrical Ratings
250V, 3 Amp
Refer to the Islatrol listing above.
150V, 80 Joule
130V, 38 Joule
275V, 75 Joule
275V, 140 Joule
0.01µf, 100 , 600VAC
I - 115 (15A, 120VAC)
Part Number
0804-0196-0000
0802-0273-0000
0802-0304-0000
0802-0266-0000
0802-0405-0000
0804-0147-0000
Appendix