Gai-tronics 12578-002 Monitored Input Module (MIM) Manual do Utilizador descarregar pdf (Página 6)

Pub. 42004-711L2B

Model 12578-002 Monitored Input Module (MIM) Page 6 of 12

f:\standard ioms - current release\42004 instr. manuals\42004-711l2b.doc

01/09

Model 2: IDC Single Normally-Open (N.O.) Switch

In this configuration, only one normally-open dry contact closure may be installed per supervised line. In

this mode, the loop is monitored for open circuits, wire-to-wire short circuits (across + and -), and ground

faults. When the contact closure is not active (open), the loop appears as 20.1 kΩ load (15 kΩ in series

with 5.1 kΩ). This appears on the input to the MIM and indicates a healthy loop. When the contact

closure is active (closed), the 15 kΩ resistor is bypassed.

Figure 3. IDC Single Normally-Open Switch

The circuit then sees only the 5.1 kΩ load. This changes the value of the input and indicates to the MIM

that the contact closure is active. If there is a short across + and -, if either leg is grounded, or if a break

occurs on either leg, the MIM indicates that a fault has occurred.

OTE: The terminating resistors are not included with the MIM. These resistors are included in a kit

(12509-003) that must be ordered separately.

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Gai-tronics 12578-002 Monitored Input Module (MIM) Manual do Utilizador Página 6