Precision Digital PD138 - Manual (Page 17)

PD138 Minimux
®
II Temp & Process Scanner Instruction Manual
17
ALARM-IN CONNECTIONS
Each channel on the PD138 has its own Alarm-In line that provides
independent alarm indication capability for each channel. The alarm
input lines of the PD138 are normally high (pull-up to 5V). Relay contacts
from a Precision Digital meter or a low level logic output from a PLC can
be used to drive the PD138 alarm input lines.
Note:
Under normal condition the NC contact of the PD6000 is opened
(failsafe). When the PD6000 goes to alarm the corresponding relay
transfers connecting the NC and C contacts together causing an alarm
condition to be detected on the PD138.