Emerson Rosemount 56, Instruction Manual

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Instruction Manual Section 9: Alarm Relay Functions
LIQ-MAN-56 April 2017
Alarm Relay Functions 67
Section 9.0 Alarm Relay Functions
9.1 General
An alarm is a relay that closes a set of contact points (a switch) inside the analyzer. In doing
so, the relay closes an electrical circuit and turns on a device wired to the contacts. The 56
Advanced Analyzer has four alarm relays and seven relay control functions. The relays are
turned on and off by the analyzer based on the control points, setpoints or control
parameters that you program into the analyzer through the keypad. See Section 9.2
through 9.7 to program the alarm relay functions. Each relay functions section includes a
description, a figure detailing its operation, a step-by-step setup procedure, and a table or
default and programmable limit settings.
The 56 has the following relay control functions:
9.2 High/Low Concentration Alarm
9.2.1 Description
High/Low concentration alarms are setpoint alarms with adjustable deadband. These
operate as simple on/off alarms used for applications requiring discrete on/off control of
pumps and valves. Typical applications include demineralizer bed regeneration and
blowdown in boilers and cooling towers. Any active device variable in the 56 analyzer can be
programmed as a high/low concentration alarm including the primary or secondary
variables, temperature, raw values and diagnostics.
A schematic of the high/low concentration (setpoint) alarm operation is shown below.
Relay Control Functions Common applications Section
High/Low Concentration Alarm measurement setpoint control Sec. 9.2
Delay Timer chemical mixing and neutralization Sec. 9.3
Bleed and Feed blowdown and chemical addition Sec. 9.4
Totalizer Relay Activation chemical dosing in reactors Sec. 9.5
Interval Timer periodic probe cleaning Sec. 9.6
Date and Time Activation seawater-cooled condensers Sec. 9.7
Figure 9-1. High/Low Concentration Alarm operation
high alarm
t n i o p t e s
high alarm logic
1.5
1.3
deadband (0.2)
time
PV
alarm activates
alarm deactivates
Table 9-1. Alarm Relay Functions