Precision Digital PD650 - Manual (Page 72)

Model PD650 Large Display Process Meter Instruction Manual
72
Relays Operation
Overview
The relay capabilities of the meter expand its usefulness beyond simple
indication to provide users with alarm
ing and control ling functions. These
capabilities include front panel alarm status LEDs as well as either 2 or 4 optional
relays. Typical applications include high or low temperature, level, pressure or
flow alarms, simple control applications like sump-pump or tank-filling and
automatic or manual batch controlling. There are four basic ways the relays can
be used:
1. High or Low Alarms
2. Simple On/Off Control with 100%
aA djustable Dd eadband
3. Automatic Batch Control
4. Manual
Batch Control
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. For instance, if the meter is powered up
and reads 500, the following table indicates how the alarm LEDs and relays will
react based on the various set and reset points:
Alarm # HI or LO
Set
Point
Reset
Point
Power-up
Reading
Relay &
LED
1 HI 1000 500 499 Off
2 LO 700 900 500 On
3 LO 250 400 500 Off
4 HI 450 200 500 On
Fail-Safe Operation
The following table indicates how the relays behave based on Jumper J5 being
installed or not installed:
Jumper J5 on
Options Board Fail-Safe Relay Coils
Energized in Power Failure
On Enabled Non-alarm state Relays go to
alarm state
Off Disabled Alarm state Relays go to
non-alarm state