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Helios PD2-6100 Strain Gauge, Load Cell, and mV Meter
Relay Operation Details
Overview
The four-relays option for the meter expands its
usefulness beyond simple indication to provide users
with alarm and control functions. Typical applications
include high and low force, level, or pressure alarms,
control applications such as simple on/off control, and
relay alternation control for up to 4 pumps. There are
four basic ways the relays can be used:
1.
High and Low Alarms with Latching or Non-
Latching Relays
2.
Simple On/Off Control with 100% Adjustable
Deadband
3.
Sampling (Based on Time)
4.
Alternation Control for up to 4 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.
HI or LO
Set
Alarm #
Alarm
Point
1
HI
1000
2
LO
700
3
LO
250
4
HI
450
Fail-Safe Operation
The following table indicates how the relays behave
based on the fail-safe selection for each relay:
Fail-Safe
Non-Alarm State
Selection
NO
NC
Off
Open
Closed
On
Closed
Open
Note: NO = Normally Open, NC = Normally Closed.
This refers to the condition of the relay contacts
when the power to the meter is off.
Power-
Reset
Relay &
Up
Point
LED
Reading
500
499
Off
900
499
On
400
499
Off
200
499
On
Alarm State
Power
Failure
NO
NC
Closed
Open
Relays
go to
non-
alarm
state
Open
Closed
Relays
go to
alarm
state
Front Panel LEDs
The alarm status LEDs on the front panel are
available on all meters, even those without relays
installed, and provide status indication for the
following:
LED
1
2
3
4
The meter is supplied with four alarm points that
include front panel LEDs to indicate alarm conditions.
This standard feature is particularly useful for alarm
applications that require visual-only indication. The
LEDs are controlled by the set and reset points
programmed by the user. When the display reaches a
set point for a high or low alarm, the corresponding
alarm LED will turn on. When the display returns to
the reset point the LED will go off. The front panel
LEDs respond differently for latching and non-latching
relays.
For non-latching relays, the LED is always off during
normal condition and always on during alarm
condition, regardless of the state of the relay (e.g.
Relay acknowledged after alarm condition).
For latching relays, the alarm LEDs reflect the status
of the relays, regardless of the alarm condition. The
following tables illustrate how the alarm LEDs function
in relation to the relays and the acknowledge button
(Default: F3 key assigned to ACK).
Latching and Non-Latching Relay
Operation
The relays can be set up for latching (manual reset)
or non-latching (automatic reset) operation.
Relay terminology for following tables
Terminology
On
Off
Ack
The On and Off terminology does not refer to the
status of the relay's coil, which depends on the fail-
safe mode selected.
•
In latching relay mode, if Fail-Safe is off, latched
relays will reset (unlatch) when power is cycled.
37
Instruction Manual
Status
Alarm 1
Alarm 2
Alarm 3
Alarm 4
Relay Condition
Alarm (Tripped)
Normal (Reset)
Acknowledged
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