Model PD6000 Analog Input Process Meter Instruction Manual
50
Relay Operation Details
Overview
The relay capabilities of the meter expand its usefulness beyond simple
indication to provide users with alarm and control functions. These ca-
pabilities include front panel alarm status LEDs as well as either 2 or 4
optional internal relays and/or 4 external relays expansion module. Typ-
ical applications include high or low temperature, level, pressure or flow
alarms, control applications such as simple on/off pump control, and
pump alternation control for up to 8 pumps. There are four basic ways
the relays can be used:
1. High or Low Alarms with Latching or Non-Latching Relays
2. Simple On/Off Control with 100% Adjustable Deadband
3. Sampling (Based on Time)
4. Pump Alternation Control for up to 8 Pumps
Relays Auto Initialization
When power is applied to the meter, the front panel LEDs and alarm
relays will reflect the state of the input to the meter. The following table
indicates how the alarm LEDs and relays will react on power-up based
on the set and reset points:
Alarm
#
HI or LO
Alarm
Set
Point
Reset
Point
Power-Up
Reading
Relay &
LED
1 HI 1000
500 499 Off
2 LO 700 900 499 On
3 LO 250 400 499 Off
4 HI 450 200 499 On
Fail-Safe Operation
The following table indicates how the relays behave based on the fail-
safe selection for each relay:
Fail-Safe
Selection
Non-Alarm State
Alarm State
Power Failure
NO NC NO NC
Off Open
Closed
Closed
Open
Relays
go
to
non-alarm state
On Closed
Open
Open
Closed
Relays
go
to
alarm state
Note: NO = Normally Open, NC = Normally Closed. This refers to the
condition of the relay contacts when the power to the meter is off.
