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Set reference temperature values for specific gravity using
the Field Communicator
When Derived Variable is set to Specific Gravity, you must set the reference temperature to be
used for density measurement and the reference temperature of water, and then verify
the density of water at the configured reference temperature. The two reference
temperature values affect specific gravity measurement.
Additionally, the two reference temperature values affect any concentration process
variable that is calculated by equation, rather than by matrix, because the equations are
based on specific gravity.
Typically, the two reference temperature values are the same, but this is not required.
Restriction
If Derived Variable is not set to Specific Gravity, do not change any of these values. These are set by the
active concentration matrix. To check the setting of Derived Variable, choose Configure > Manual Setup >
Measurements > Optional Setup > Concentration Measurement > CM Configuration.
Important
Do not change the setting of Derived Variable. If you change the setting of Derived Variable, all existing
concentration matrices will be deleted from transmitter memory.
Procedure
1. Choose Configure > Manual Setup > Measurements > Optional Setup > Concentration
Measurement > Configure Matrix.
2. Set Matrix Being Configured to the matrix you want to modify.
3. Choose Reference Conditions, then perform the following actions:
a. Set Reference Temperature to the temperature to which line density will be
corrected for use in the specific gravity calculation.
b. Set Water Reference Temperature to the water temperature that will be used in the
specific gravity calculation.
c. Set Water Reference Density to the density of water at the specified reference
temperature.
The transmitter automatically calculates the density of water at the specified
temperature. The new value will be displayed the next time that transmitter
memory is read. You can enter a different value if you want to.
Related information
Using equations to calculate specific gravity, °Baumé, °Brix, °Plato, and °Twaddell
Configure process measurement
Configuration and Use Manual 75