Watlow SDMA Card Shorted Solid State Relay Detector - Manual

There is concern that if a solid state relay fails, it will
most likely fail in a shorted condition. To minimize this
concern, Watlow Controls has designed a low-cost card
(Watlow P/N 09-2313) that provides a shorted SSR
alarm. It is designed to be used with DC input SSRs,
rated 10 to 40 amps on either a single phase or three-
phase, two-leg system. In addition to the SDMA card, we
strongly recommend semiconductor fuses to protect the
SSR, and a high limit cutout to protect the thermal
system from any runaway conditions. The SDMA card mounts directly on the solid state relay
and takes its power from the current flowing through the
current transformer. If there is no input command signal
from the temperature control to the SSR, and there is
current flow through the heater, the mechanical relay
alarm output will de-energize. This can be wired through
a customer supplied latching relay and alarm to 120 or
240 volts. Output contact rating of the SDMA mechanical
relay is 0.5 amperes maximum.
Watlow Controls
1241 Bundy Blvd., P.O. Box 5580
Winona, MN 55987-5580
Phone: 507-454-5300, Fax: 507-452-4507
SDMA Card
Shorted Solid State Relay Detector
Data Sheet
0600-0028-0006 Rev A (1632) Made in the U.S.A.
January, 1999
Figure 1 - SDMA Card Dimensions
NOTE: Mount with two 6-32 screws 5/8”
long. (Included with the SDMA card.)