Measurement Computing CIO-PDISO8 - Manual (Page 14)

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Chapter 3
Functional Details
Relay outputs
Form C relays
The Form C relay has a common, normally open (NO) and normally closed (NC) contact. Figure 8 shows the
schematic for a Form C relay, like those connected at relay 0 through relay 4.
Figure 8. Form C Relay (0) contacts
 When 0 is written to the output, the common and NC are in contact.
 When 1 is written to the output, the common and NO are in contact.
Form A relays
The Form A relay has a common and a normally open (NO) contact. Figure 9 shows the schematic for a Form A
relay, like those connected at relay 5 through relay 7.
Figure 9. Form A Relay (5) contacts
 When 0 is written to the output, the common and NO are NOT in contact.
 When 1 is written to the output, the common and NO are in contact.
The Form A and Form C relays on the CIO-PDISO8 board are the same type. Only the connections to the relay
poles differ.