Overview
The HART variables are a set of four variables predefined for HART use. The HART variables
include the Primary Variable (PV), Secondary Variable (SV), Tertiary Variable (TV), and
Quaternary Variable (QV). You can assign specific process variables to the HART variables,
and then use standard HART methods to read or broadcast the assigned process data.
Tip
The Tertiary Variable and Quaternary Variable are also called the Third Variable (TV) and Fourth
Variable (FV).
Restriction
One some devices, the PV is fixed to a specific process variable and cannot be changed.
Options for HART variables
Options for HART variablesTable 6-7:
Process variable
Primary Varia-
ble (PV)
Secondary
Variable (SV)
Third Variable
(TV)
Fourth Varia-
ble (QV )
Standard
Line Density
(1)
✓ ✓ ✓ ✓
Line Temperature ✓ ✓ ✓ ✓
Case Temperature ✓ ✓ ✓ ✓
Tube-Case Temperature Difference ✓ ✓ ✓ ✓
Line Temperature (External) ✓ ✓ ✓ ✓
Line Pressure (External) ✓ ✓ ✓ ✓
Drive Gain ✓ ✓ ✓ ✓
Sensor Time Period ✓ ✓ ✓ ✓
Velocity ✓ ✓ ✓ ✓
User-Defined Calculation Output ✓ ✓ ✓ ✓
Board Temperature ✓ ✓
Input Voltage ✓ ✓
API referral
Referred Density (API) ✓ ✓ ✓ ✓
Concentration measurement
Specific Gravity ✓ ✓ ✓ ✓
Concentration ✓ ✓ ✓ ✓
Integrate the meter with the control system
96 Micro Motion
®
Compact Density Meters (CDM)
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