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Reference Manual
00809-0100-4102, Rev AA
Section 2: Configuration
May 2013
Configuration
2.6 Configure for Level and Flow
2.6.1 Configuring scaled variable
The Scaled Variable configuration allows the user to create a relationship/conversion between
the pressure units and user-defined/custom units. There are two use cases for Scaled Variable.
The first use case is to allow custom units to be displayed on the transmitter's LCD Display. The
second use case is to allow custom units to drive the transmitter's PV output.
If the user desires custom units to drive the PV output, Scaled Variable must be re-mapped as
the primary variable. Refer to “Re-Mapping device variables” on page 18.
The Scaled Variable configuration defines the following items:
Scaled Variable units - Custom units to be displayed.
Scaled data options - Defines the transfer function for the application
– Linear
– Square root
Pressure value position 1 - Lower known value point with consideration of linear offset.
Scaled Variable value position 1 - Custom unit equivalent to the lower known value
point.
Pressure value position 2 - Upper known value point
Scaled Variable value position 2 - Custom unit equivalent to the upper known value
point
Linear offset - The value required to zero out pressures affecting the desired pressure
reading.
Low flow cutoff - Point at which output is driven to zero to prevent problems caused by
process noise. It is highly recommended to use the low flow cutoff function in order to
have a stable output and avoid problems due to process noise at a low flow or no flow
condition. A low flow cutoff value that is practical for the flow element in the
application should be entered.
Configuring Scaled Variable using a Field Communicator
1. Follow the screen prompts to configure Scaled Variable.
a. When configuring for level, select Linear under Select Scaled data options.
b. When configuring for flow, select Square Root under Select Scaled data options.
Configuring Scaled Variable using AMS Device Manager
Right click on the device and, select Configure.
1. Select the Scaled Variable tab and click the Scaled Variable button.
2. Follow screen prompts to configure Scaled Variable
From the HOME screen, enter the fast key sequence
Device Dashboard Fast Keys
2, 1, 7