Operation
2.3
Power Supply
Power shall be supplied to the transmitter circuit using the signal line (2-wire system). The transmitter
quiescent consumption is 3.6 mA; during operation, consumption may be as high as 21 mA, depending
on the measurement and sensor status.
The LD301 in the transmitter mode shows failure indication at 3.6 mA if configured for low signal failure;
at 21 mA, if configured for high signal failure; 3.8 mA in the case of low saturation; 20.5 mA in the case
of high saturation and measurements proportional to the applied pressure in the range between 3.8 mA
and 20.5 mA. 4 mA corresponds to 0% of the working range and 20 mA to100 % of the working range.
Power Supply Isolation
The sensor power supply is isolated from the main circuit by this module.
Display Controller
It receives the data from the CPU and actives the LCD segments. It also activates the back plane and
the control signals for each segment.
Local Adjustment
Two switches on the main board are magnetically activated by inserting the magnetic tool.
Functional Description - Software
Refer to the block diagram Figure 2.3. The function of each block is described below.
Digital Filter
The digital filter is a low pass filter with an adjustable time constant. It is used to smooth noisy signals.
The Damping value is the time required for the output reaching 63.2% for a step input of 100%.
This value (in seconds) may be freely configured by the user.
Factory Characterization
The actual pressure from the capacitance and temperature readouts obtained from the sensor can
be calculated by using the factory characterization data stored in the sensor EEPROM.
User Linearization
The characterization TRIM points P1 - P5 can be used to complement the transmitter original
characterization.
Pressure Trim
The values obtained by Zero Pressure TRIM and Upper Pressure TRIM may correct here the
transmitter for long term drift or the shift in zero or upper pressure reading due to installation or over
pressure.
Ranging
It used to set the pressure values corresponding to the 4 and 20 mA output. In transmitter mode the
LOWER-VALUE is the point corresponding to 4 mA, and the UPPER-VALUE is the point corresponding
to 20 mA. In PID mode the LOWER-VALUE corresponds to MV = 0% and the UPPER-VALUE
corresponds to MV = 100%, where, MV is the Manipulated Variable.
Function
Depending on the application, the transmitter output or controller PV may have the following
characteristics according to the applied pressure: Linear (for pressure, differential pressure and level
measurement); Square-root (for flow measurement with differential pressure producers) and Square-
root of the Third and Fifth power (for flow measurements in open channels). The function is selected
with FUNCTION.
Points Table
This block relates the output (4-20 mA or Process Variable) to the input (applied pressure) according to
a look-up table from 2 to 16 points. The output is calculated by the interpolation of these points. The
points are given in the function "TABLE POINTS" in percent of the range (X
i
) and in percent of the
output (Y
i
). It may be used to linearize, e.g., a level measurement to volume or mass. In flow
measurement it can be used to correct varying Reynolds numbers.
Setpoint
Is the desired value in the process variable when the controller is activated. The operator in the
\CONTR\INDIC option adjusts it.
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