11
Install and Wire, Chapter 2
WATLOW Series 942 User's Manual
Output 1 Wiring
Figure 12 -
Solid State Relay
With Contact
Suppression,
Output 1 Wiring.
NOTE:
This output is sup-
plied with an arc
suppression snub-
ber across the out-
put terminals. High
impedance loads
may remain ener-
gized even though
the output device is
turned OFF.
Figure 13 -
Switched DC
(Open Collector),
Output 1 Wiring.
Switched DC Output (Open Collector), Output 1
Model # 942A - _
C
_ _ - _ 000
Switched DC
Watlow's solid state switch is a low current DC output (open collector) used to switch an
external power switching device such as an SSR or an electromechanical relay. The input
specifications of the power switching device must match those listed for the SS switch
output. The power switching device must provide isolation between the SS switch output
and load power since the SS switch output is a non-isolated output. Minimum load resis-
tance is 500
Ω
. Available current is 22mA maximum. Typical voltage drop across a 1K
Ω
load is 12 to 19 volts.
-
+
17
16
Switched DC, Open Collector, Non-Isolated
Logic
Switch
External
Load
+
-
N.O.
COM.
External
Load
Fuse
L1
L2
18
17
Solid State Relay, Form A, 0.5 Amp
Solid State Relay With Contact Suppression, Output 1
Model # 942A -
_
B
_ _ - _ 000
Solid State Relay With Contact Suppression
Watlow's solid state relay changes state at zero volts, which is "zero-cross switching." They
are also optically isolated, which means the output circuitry is energized by infrared light
striking a photosensitive device. This results in a virtual absence of electrically generated
noise, and provides electrical isolation between the input and output. For use in switching
mercury relays or small AC loads.
Off state impedance is 20K
Ω
minimum.
