"Islatros"
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
lslatrol
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.
lslatrols
are available from:
Control Concepts Corporation
328 Water Street
P.O. Box 1360
Blnghamton, NY
139O2-1360
Phone:
607/724-2464
I
-
101 (1A,l20VAC)
I
-
202
(2.5A,
208/240VAC)
I
-
105
(5A,
120VAC)
I
-
207
(7.5A,
208/240VAC)
I
-
115
(15A,
120VAC)
The ultimate protection is an
“uninterruptable”
power supply.
This
'senses'
the A.C. power line; when the line fluctuates, a battery powered
6OHz
in-
verted circuit takes over, supplying power within
one-half
to one cycle of the
A.C. line; very expensive.
How To Check For Ground Loops
To check for ground loops, disconnect the ground wire at the ground
termina-
tion.
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
continu-
ity, you must now begin looking for the ground loops. Begin disconnecting
grounds in the system one at a time, checking for continuity after each discon-
nection. 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
Electrical Ratlngs Part Number
Common Mode Line
Filter
25OV,
3 Amp 0804-0196-0000
Differential
Mode Line Filter
Refer to the
lslatrol
listing above.
Metal Oxide
Varistor
15OV,
80 Joule
0802-0273-0000
MOV
13OV,38
Joule 0802-0304-0000
802-0304-0000
MOV
275V,
75 Joule
0802-0266-0000
MOV
275V,
140 Joule
0802-0405-0000
Table
1
-
NoiseSuppressIon
Device
Ratings
Install and Wire, Chapter 2
WATLOW
Series
98O/985
User’s Manual
9