Measurement-computing E-PDISO16 Manuel d'utilisateur télécharger pdf (Page 17)

E-PDISO16 User's Guide Functional Details

Relay output terminals (NO0 to NC15)

The E-PDISO16 provides 16 Form C electromechanical relay outputs. The Form C relay has a common (C),

normally open (NO) and normally closed (NC) contact.

The screw terminals labeled

NO0 to NC7 connect to the NO, C, and NC contacts for relays 0 through 7. The

screw terminals labeled

NO8 to NC15 connect to the NO, C, and NC contacts for relays 8 through 15.

Form C relay output

A schematic for Form C relay contacts is shown in . Figure 3-2

Figure 3-2. Form C relay contacts

Two 4.7 k pull-down resistor networks on the E-PDISO16 control the power-up state of each relay bank. At

power-up, the relays are put into a non-energized state (NC in contact to Common).

Relay contact protection circuit for inductive loads

If you are using the relays to control inductive loads, place a diode across the load terminals to suppress the

kickback voltage. If the diode is not present, the kickback voltage could cause the on-board processor to enter

an unstable state. To return the processor to a stable state, unplug the power cable from the E-PDISO16 and

then reconnect.

A contact protection circuit is shown in . For AC loads, install a metal oxide varistor (MOV). Figure 3-3

Figure 3-3. Relay contact protection circuit

Inductive

Load

Kickback

Diode

Relay

3-4

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 27 28

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Measurement-computing E-PDISO16 Manuel d'utilisateur Page 17