VPT10-H
HART
®
PRESSURE TRANSMITTER
INSTALLATION, OPERATION, CONFIGURATION AND MAINTENANCE MANUAL
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9
1.3.
OPERATING PRINCIPLE
The main circuit of VPT10-H receives the capacitance readings (CL and CH) and temperature from the analog sensor
board. The normalized pressure signal is calculated by applying the factory compensation polynomial to the CL and
CH readings. From this value, using the sensor reading range, the pressure in the user unit (configurable) is calculated
with the relevant calibrations of zero, maximum pressure and minimum pressure.
Depending on the sensor range, user can choose the form of treatment for the pressure value: Linear, Table, Square
Root Extraction (single, triple or quintuple) or the combination between Table and Square Root Extraction. With the
option of Table, it is possible to mount a custom curve of up to 16 points, mainly used with the characterization of
volumes in tanks. The Square Root Extraction is used in the application of the mass and flow measurement transfer
function.
Figure 1.4 – Operating principle of VPT10-H.
VPT10-H still provides the ambient temperature reading as a secondary variable and the pressure reading as a tertiary
variable (even if the primary variable is set as flow measurement).
The primary variable (PV) can be configured to indicate pressure or flow according to the configured transfer function
(Linear and Table for Pressure, Square Root Extraction for Flow).
According to the type of variable to be indicated, user can also configure unit, work range, limits and alarms (for
pressure and flow, separately).
In addition, the transmitter can calculate the Totalization, considering the flow rate, according to the unit configured by
user (mass or volume in time). It is possible to reset the Totalization, enable/disable it and also set a limit value so an
alarm can be generated.