DigitalFlow™ Multipurpose Ultrasonic Liquid Flowmeter Startup Guide (1- and 2-Channel) 11
Chapter 1. Installation
1.7.5 Wiring an Alarms Option Card
The Model DF868 flowmeter can accommodate up to 4 alarm option cards. Each alarms option card includes three
Form C relays (designated as A, B and C).
The alarm relays on the option card are available in two types:
• general purpose
• hermetically sealed for Class I, Division 2 hazardous areas.
The maximum electrical ratings for the relays are listed in Chapter 4, Specifications. Each of the three alarm relays can
be wired either as Normally Open (NO) or Normally Closed (NC).
In setting up an alarm relay, it may be wired for either conventional or fail-safe operation. In fail-safe mode, the alarm
relay is constantly energized, except when it is triggered or a power failure or other interruption occurs. See Figure 6
for the operation of a NO alarm relay in both conventional and fail-safe mode.
Connect the two wires required for each alarm relay in accordance with the pin number assignments shown in
Figure 10 on page 16.
Figure 6: Conventional and Fail-Safe Operation
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