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‡ SIGNET
5900 Salinity Monitor
PPT
PPT
Low setpoint =
Adjustable hysteresis =
Relay active =
Relay inactive =
High setpoint =
Adjustable hysteresis =
Relay active =
Relay inactive =
5. Relay Operation
5.1 LOW alarm mode
The relay is active when the solution salinity in Parts Per Thou-
sand (PPT) drops below the setpoint, and is inactive when the
solution salinity rises above the setpoint plus hysteresis.
4. Relay Connections
Two internal relay contact sets (COM, NO, and NC) may be used
for external device control. Front panel LED annunciators indicate
the activation status of each relay. Each relay can control up to
two devices simultaneously. Relay operation modes include Low
alarm, High alarm, and Proportional Pulse.
Common device connections include:
• Pulse mode - metering pump control
• Pulse mode - solenoid valve control
• Low or High mode - warning lamps
• Low or High mode - bells or sirens
• Low or High mode - external heavy-duty relay
Wiring Example (right)
Device A is powered when relay 2 is inactive (front panel LED
"off"). Power is discontinued when the relay 2 setpoint is reached
(front panel LED "on"). Device B is not powered when relay 2 is
inactive. Power is applied after the relay 2 setpoint is reached.
+
-
-
Device
A
External AC/DC
power
+
-
+
Device
B
Relay 1
Relay 2
NC
C
NO
NC
C
NO
5900 Terminals
NO C NC
Relay
Inactive
Relay
Active
NO C NC
Technical Notes:
•
Maximum relay contact ratings: 5 A @ 30 VDC, 5 A @ 125
VAC, or 3 A @ 250 VAC
•
An external heavy-duty relay must be used for devices with
surge currents or operating currents that exceed the above
specifications.
5.2 HIGH alarm mode
The relay is active when the solution salinity (PPT) rises above
the setpoint, and is inactive when the solution salinity drops below
the setpoint plus hysteresis.
5.3 Proportional PULSE mode
The proportional pulse relay configuration is primarily designed for metering pump control. The operator is prompted to enter a minimum
and maximum salinity setpoint and maximum pulse rate for the assigned relay. Relay pulse width is fixed at 130 ms.
•
Metering pump chemical addition (dry contact activation type required)
Relay 1
or Relay 2
10
PPT
30
PPT
0 pulses
PPT
Relay 1
or Relay 2
30
PPT
10
PPT
PPT
300 pulses
300 pulses
0 pulses
Relay 1 Rate:
300 Pulses/min >
Relay 1: Pulse
10.0000 30.0000>
Relay 1: Pulse
30.0000 10.0000>
Relay 1 Rate:
300 Pulses/min >
Example 1:
As the process salinity (PPT) rises above the
minimum pulse setpoint (10 PPT) the relay begins pulsing,
triggering the metering pump for deionized water addition. As the
process salinity continues to rise, pulsing accelerates proportion-
ally until the maximum programmed pulse rate of 300 pulses/
minute and setpoint (30 PPT) is reached, forcing the process
salinity back down to intended levels (e.g. < 10 PPT).
Example 2:
As the process salinity (PPT) falls below the minimum
pulse setpoint (30 PPT) the relay begins pulsing, triggering the
metering pump for chemical addition. As the process salinity
continues to decrease, pulsing accelerates proportionally until the
maximum programmed pulse rate of 300 pulses/minute and
setpoint (10 ppt) is reached, forcing the process salinity back up to
intended levels (e.g. < 30 PPT).
