Large Display Temperature Meters
Instruction Manual
42
Relays Operation
Overview
The relay option added to the Digital Temperature Meter expands its usefulness
beyond simple indication to provide users with alarms and simple on/off
temperature controlling functions. There are two basic ways the relays can be
used:
1. High or low alarms with latching or non-latching relay operation.
2. Simple on/off temperature control with 100% adjustable deadband.
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 PCB
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
