The signal from the mA output indicates the current state of the process:
•
12 mA: Single-phase flow
•
16 mA: Moderate two-phase flow
•
20 mA: Severe two-phase flow
6.3 Configure Flow Rate Switch
Display
Menu
>
Configuration
>
Alert Setup
>
Enhanced Events
>
Flow Rate Switch
ProLink III
Device Tools
>
Configuration
>
I/O
>
Outputs
>
Discrete Output
>
Source
>
Flow Switch Indication
Field Communicator
Configure
>
Manual Setup
>
Inputs/Outputs
>
Channel
x
>
Discrete Output
x
>
Flow Switch
Flow Rate Switch
is used to indicate that the flow rate has moved past a user-specified setpoint, in either
direction. The flow rate switch is implemented with a user-configurable hysteresis.
Typically, a Discrete Output is assigned as the flow rate switch indicator. The Discrete Output can be wired to
an external device such as a light or a horn.
Prerequisites
A channel must be configured as a Discrete Output, and the Discrete Output must be available for this use.
Procedure
1. Set
Discrete Output Source
to Flow Switch, if you have not already done so.
2. Set
Flow Switch Variable
to the flow variable that you want to use to control the flow rate switch.
3. Set
Flow Switch Setpoint
to the value at which the flow switch will be triggered (after
Hysteresis
is
applied).
•
If the flow rate is below this value, the Discrete Output is ON.
•
If the flow rate is above this value, the Discrete Output is OFF.
4. Set
Hysteresis
to the percentage of variation above and below the setpoint that will operate as a
deadband.
Hysteresis
defines a range around the setpoint within which the flow rate switch will not change.
•
Default: 5%
•
Range: 0.1% to 10%
Example
If
Flow Switch Setpoint
=
100
g/sec and
Hysteresis
=
5%
, and the first measured flow rate is above
100 g/sec, the discrete output is OFF. It will remain OFF unless the flow rate drops below 95 g/sec. If
this happens, the discrete output will turn ON, and remain ON until the flow rate rises above 105 g/sec.
At this point it turns OFF and will remain OFF until the flow rate drops below 95 g/sec.
Related information
Configuration and Use Manual
Configure advanced options for process measurement
MMI-20025166
March 2019
Configuration and Use Manual
107