Measurement Computing USB-ERB24 User Manual
Page 19
USB-ERB24 User's Guide
Functional Details
The relay contacts associated that are with each relay location are listed in
.
Table 3-4
Table 3-4. Relay locations and associated contacts
R35, R36, R41, R43, R45, R47, R49, R51, R87, R89, R91, R93, R96,
R98, R100, R102, R103, R105, R107, R109, R112, R114, R116, R118
Relays NO contact pull-up (to USB +5 V) /
pull-down, user installed.
R37, R40, R42,R44, R46, R48, R50, R52, R88, R90, R92, R94, R95,
R97, R99, R101, R104, R106, R108, R110, R111, R113, R115, R117
Relays NC contact pull-up (to USB +5 V) /
pull-down, user installed
Relay contact protection circuit for inductive loads
When you connect an inductive load to a relay, energy stored in the inductive load can induce a large voltage
surge when you switch the relay. This voltage can severely damage the relay contacts. To limit the voltage
surge across the inductive load in a DC circuit, install a kickback diode across the inductive load. Refer to the
contact protection circuit in F
. For AC loads, install a metal oxide varistor (MOV).
Figure 3-7. Relay contact protection circuit
C
V
Inductive
Load
Kickback
Diode
NC
+
-
NO
Relay
3-5