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Operation of electronics with HART communication
Function diagram of electronics
The input pressure is converted into an electrical signal by the sensor (1). This signal is amplified by the measuring amplifier (2) and digitalized in an analog-to-digital converter (3). The digital signal is analyzed in a microcontroller (4) and corrected according to linearity and thermal characteristics. In a digital-to-analog converter (5) it is then converted into the output current of 4 to 20 mA. A diode circuit provides reverse polarity protection. You can make an uninterrupted current measurement with a low-ohm ammeter at the connection (10). The data specific to the measuring cell, the electronic data and parameter settings are stored in two non-volatile memories (6). The first memory is linked to the measuring cell, the second to the electronics.
The buttons (8) can be used to call up individual functions, so-called modes. If you have a device with a display (9), you can use this to track mode settings and other messages. The basic mode settings can be changed with a computer via the HART modem (7).
Operation of electronics with PROFIBUS PA communication
Function diagram of electronics
The input pressure is converted into an electrical signal by the sensor (1). This signal is amplified by the measuring amplifier (2) and digitalized in an analog-to-digital converter (3). The digital signal is analyzed in a microcontroller (4) and corrected according to linearity and thermal characteristics. It is then made available at the PROFIBUS PA over an electrically isolated PROFIBUS PA interface (7). The data specific to the measuring cell, the electronic data and parameter settings are stored in two non-volatile memories (6). The first memory is linked to the measuring cell, the second to the electronics.
The buttons (8) can be used to call up individual functions, so-called modes. If you have a device with a display (9), you can use this to track mode settings and other messages. The basic mode settings can be changed with a computer over the bus master (12).
Operation of electronics with FOUNDATION Fieldbus communication
Function diagram of electronics
The bridge output voltage created by the sensor (1, Figure "Function diagram of electronics") is amplified by the measuring amplifier (2) and digitized in the analog-to-digital converter (3). The digital information is evaluated in the microcontroller, its linearity and temperature response corrected, and provided on the FOUNDATION Fieldbus through an electrically isolated FOUNDATION Fieldbus interface (7).
The data specific to the measuring cell, the electronics data, and the parameter data are stored in the two non-volatile memories (6). The one memory is coupled to the measuring cell, the other to the electronics. As the result of this modular design, the electronics and the measuring cell can be replaced separately from each other.
Using the three input buttons (8) you can parameterize the pressure transmitter directly at the measuring point. The input buttons can also be used to control the view of the results, the error messages and the operating modes on the display (9).
The results with status values and diagnostic values are transferred by cyclic data transmission on the FOUNDATION Fieldbus. Parameterization data and error messages are transferred by acyclic data transmission. Special software such as National Instruments Configurator is required for this.
Mode of operation of the measuring cells
The process connections available include the following:
- G
- -14 NPT
- Flush-mounted diaphragm:
- Flanges to EN
- Flanges to ASME
- NuG and pharmaceutical connections
Measuring cell for gauge pressure
Measuring cell for gauge pressure, function diagram
The input pressure (pe) is transferred to the gauge pressure sensor (6) via the seal diaphragm (4) and the filling liquid (5), displacing its measuring diaphragm. The displacement changes the resistance value of the four piezo resistors in the measuring diaphragm in a bridge circuit. The change in the resistance causes a bridge output voltage proportional to the input pressure.
Transmitters with spans 63 bar ( 926.1 psi) measure the input pressure compared to atmospheric, transmitters with spans of 160 bar ( 2352 psi) compared to a vacuum.
Measuring cell for absolute pressure
Measuring cell for absolute pressure, function diagram
The input pressure (pe) is transferred to the absolute pressure sensor (5) via the seal diaphragm (3) and the filling liquid (4), displacing its measuring diaphragm. The displacement changes the resistance value of the four piezo resistors in the measuring diaphragm in a bridge circuit. The change in the resistance causes a bridge output voltage proportional to the input pressure.
Measuring cell for gauge pressure, flush-mounted diaphragm
Measuring cell for gauge pressure, flush-mounted diaphragm, function diagram
The input pressure (pe) is transferred to the gauge pressure sensor (6) via the seal diaphragm (4) and the filling liquid (5), displacing its measuring diaphragm. The displacement changes the resistance value of the four piezo resistors in the measuring diaphragm in a bridge circuit. The change in the resistance causes a bridge output voltage proportional to the input pressure.
Transmitters with spans 63 bar ( 926.1 psi) measure the input pressure compared to atmospheric, transmitters with spans of 160 bar ( 2352 psi) compared to a vacuum.
Measuring cell for absolute pressure, flush-mounted diaphragm
Measuring cell for absolute pressure, flush-mounted diaphragm, function diagram
The input pressure (pe) is transferred to the absolute pressure sensor (5) via the seal diaphragm (3) and the filling liquid (4), displacing its measuring diaphragm. The displacement changes the resistance value of the four piezo resistors in the measuring diaphragm in a bridge circuit. The change in the resistance causes a bridge output voltage proportional to the input pressure.
Parameterization
Depending on the version, there are a range of options for parameterizing the pressure transmitter and for setting or scanning the parameters.
Parameterization using the input buttons (local operation)
With the input buttons you can easily set the most important parameters without any additional equipment.
Parameterization using HART communication
Parameterization using HART communication is performed with a HART Communicator or a PC.
Communication between a HART Communicator and a pressure transmitter
When parameterizing with the HART Communicator, the connection is made directly to the 2-wire cable.
HART communication between a PC communicator and a pressure transmitter
When parameterizing with a PC, the connection is made through a HART modem.
The signals needed for communication in conformity with the HART 5.x or 6.x protocols are superimposed on the output current using the Frequency Shift Keying (FSK) method.
Adjustable parameters on SITRANS P300 with HART communication
|
Parameters |
Input buttons |
HART communication |
|---|---|---|
|
Start of scale |
x |
x |
|
Full-scale value |
x |
x |
|
Electrical damping |
x |
x |
|
Start-of-scale value without application of a pressure ("Blind setting") |
x |
x |
|
Full-scale value without application of a pressure ("Blind setting") |
x |
x |
|
Zero adjustment |
x |
x |
|
current transmitter |
x |
x |
|
Fault current |
x |
x |
|
Disabling of buttons, write protection |
x |
x 1) |
|
Type of dimension and actual dimension |
x |
x |
|
Input of characteristic |
x |
|
|
Freely-programmable LCD |
x |
|
|
Diagnostic functions |
x |
1) Cancel apart from write protection
Diagnostic functions for SITRANS P300 with HART communication
- Zero correction display
- Event counter
- Limit transmitter
- Saturation alarm
- Slave pointer
- Simulation functions
- Maintenance timer
Available physical units of display for SITRANS P300 with HART communication
Table style: Technical specifications 2
|
Physical variable |
Physical dimensions |
|
Pressure (setting can also be made in the factory) |
Pa, MPa, kPa, bar, mbar, torr, atm, psi, g/cm2, kg/cm2, inH2O, inH2O (4 °C), mmH2O, ftH2O (20 °C), inHg, mmHg |
|
Level (height data) |
m, cm, mm, ft, in |
|
Volume |
m3, dm3, hl, yd3, ft3, in3, US gallon, lmp. gallon, bushel, barrel, barrel liquid |
|
Mass |
g, kg, t, lb, Ston, Lton, oz |
|
Temperature |
K, °C, °F, °R |
|
Miscellaneous |
%, mA |
Parameterization through PROFIBUS PA interface
Fully digital communication through PROFIBUS PA, profile 3.0, is particularly user-friendly. The PROFIBUS connects the SITRANS P30 0 PA to a process control system, e. g. SIMATIC PSC 7. Communication is possible even in a potentially explosive environment.
For parameterization through PROFIBUS you need suitable software, e. g. SIMATIC PDM (Process Device Manager)
Parameterization through FOUNDATION Fieldbus interface
Fully digital communication through FOUNDATION Fieldbus is particularly user-friendly. Through the FOUNDATION Fieldbus the P300 is connected to a process control system. Communication is possible even in a potentially explosive environment.
For parameterization through the FOUNDATION Fieldbus you need suitable software, e. g. National Instruments Configurator.
Adjustable parameters for SITRANS P300 PA and FOUNDATION Fieldbus
|
Adjustable parameters |
Input buttons |
PROFIBUS PA and FOUNDATION Fieldbus interface |
|---|---|---|
|
Electrical damping |
x |
x |
|
Zero adjustment (correction of position) |
x |
x |
|
Buttons and/or function disabling |
x |
x |
|
Source of measured-value display |
x |
x |
|
Physical dimension of display |
x |
x |
|
Position of decimal point |
x |
x |
|
Bus address |
x |
x |
|
Adjustment of characteristic |
x |
x |
|
Input of characteristic |
x |
|
|
Freely-programmable LCD |
x |
|
|
Diagnostic functions |
x |
Diagnostic functions for SITRANS P300 PA and FOUNDATION Fieldbus
- Event counter
- Slave pointer
- Maintenance timer
- Simulation functions
- Display of zero correction
- Limit transmitter
- Saturation alarm
Physical dimensions available for the display
|
Physical variable |
Physical dimensions |
|
Pressure (setting can also be made in the factory) |
Mpa, kPa, Pa, bar, mbar, torr, atm, psi, g/cm2, kg/cm2, mmH2O, mmH2O (4 °C), inH2O, inH20 (4 °C), ftH2O (20 °C), mmHg, inHg |
|
Level (height data) |
m, cm, mm, ft, in, yd |
|
Mass |
g, kg, t, lb, Ston, Lton, oz |
|
Volume |
m3, dm3, hl, yd3, ft3, in3, US gallon, lmp. gallon, bushel, barrel, barrel liquid |
|
volume flow |
m3/s, m3/min, m3/h, m3/d, l/s, l/min, l/h, l/ d, Ml/d, ft3/s, ft3/min, ft3/h, ft3/d, US gallon/s, US gallon/min, US gallon/h, US gallon/d, bbl/s, bbl/min, bbl/h, bbl/d |
|
Mass flow |
g/s, g/min, g/h, g/d, kg/s, kg/min, kg/h, kg/d, t/s, t/min, t/h, /t/d, lb/s, lb/min, lb/h, lb/d, STon/s, STon/min, STon/h, STon/d, LTon/s, LTon/min, LTon/h, LTon/d |
|
Total mass flow |
t, kg, g, lb, oz, LTon, STon |
|
Temperature |
K, °C, °F, °R |
|
Miscellaneous |
% |
Hygiene version
In the case of the SITRANS P300 with 7MF812.-... flush-mounted diaphragm, selected connections comply with the requirements of the EHEDG or 3A. You will find further details in the order form. Please note in particular that the seal materials used must comply with the requirements of 3A. Similarly, the filling liquids used must be FDA-compliant.