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Intelligent pressure transmitter
Intelligent pressure transmitter
Download documentation
Smart transmitter working principle block diagram (Figure 1-1)
1.1 “δ”transmitter（Sensitive element）
Figure 1-2 “δ”
The core of the intelligent transmitter is a capacitive pressure sensor, which is called "δ"（Figure 1-2）.The sensor isa completely sealed component, the process pressure through the isolation diaphragm and filling liquid silicone oil to the sense of the diaphragm caused by displacement.The capacitance difference between the sensing diaphragm and the two capacitance plate is converted from the electronic components to the electrical signals of the second wire system of the 4 ~ DC 20mA.
The circuit board module of the intelligent transmitter is a circuit board which adopts a special integrated circuit (ASICS) and a surface packaging technology.The circuit board receives signals from the sensors and is modified and linearized.The output part of the circuit board module converts the digital signal into an analog output signal, and can communicate with the HART controller and the host computer software.
The A/D conversion circuit adopts 16 bit low power integrated circuit, and converts the analog current output of the demodulator to the digital quantity, and provides the microprocessor as the input signal.
Microprocessor control A/D and D/A conversion work, also can complete the self diagnosis and digital communication.At work, a digital pressure value is processed by the microprocessor and used as a digital storage to ensure the precision of the correction and conversion of the engineering unit.In addition, the microprocessor can also complete the sensor's linearity, range ratio, damping time and other functions.
EEPROM stores all the configuration, characteristics and digital fine-tuning of the parameters, the memory is non-volatile, so even without power, the stored data can still be maintained at any time to achieve intelligent communication.
1.2.4 D/A Transformation
D/A converts the digital signal sent by microprocessor to 4 ~ 20mA analog signal and output to the circuit.
Testing the intelligent transmitte through a communication device or any HART communication protocol to support the host computer to complete the communication protocol.The HART protocol using the industry standard BELL202 frequency phase shift keying (FSK) technology, the digital signal 1200Hz or 2200Hz in 4 ~ 20mA signal communication, signal frequency of 4 ~ 20mA process does not produce any interference.
1. High precision
2. Good stability
3.Small, light weight, strong vibration resistance
4.Compatibility is good, compatible with other companies in line with the HART agreement
5.Support the user to use the handheld 272/275 or PC debug software
6.In the instrument operation process in real-time to the instrument configuration or remote inquiry
7.The pressure signal can be processed by intelligent linearization, which can guarantee the higher measurement accuracy.
五、Technique target
Load characteristic diagram(Figure 1-3)
|
Intrinsic error |
0.2%F•S、0.5%F.S
|
|
Measurement range |
-0.1MPa～0 0～(10KPa～60MPa) （User selection）
|
|
Linearity |
≥0.2%F•S
|
|
Temperature drift |
＜±0.025%F•S/℃(0-50℃) |
|
Long term stability |
≤0.02%F•S/Year
|
|
Response time |
≤10mS |
|
Power supply |
24VDC(12VDC-36VDC) |
|
Output |
4～20mA(or O～10mA 、1～5V、 O～5V 、0～1OV) |
|
Load resistance |
RL=Vs-12V/0.023A |
|
Temperature range |
Electronic circuits:-40℃~+85℃ Sensitive components (Silicon oil): -40℃~ +104℃ (Inert oil): -18℃ ~ +71℃ |
|
Environment temperature |
-20～+85℃ |
|
Storage temperature |
-40～+55℃ |
|
Electrical interface |
M20×1.5 or 1/2NPT |
|
Protection grade |
IP67 |
|
Liquid materials |
316L、Hastelloy C276、titanium |
|
Sensor isolation diaphragm material |
316L、Hastelloy、titanium |
|
Start-up time |
Maximum damping time＜2s |
|
Electrical damping |
0～16s |
|
Weight |
3.5 kg(Does not include attachments, with the exception of the transmitter with a flange) |
|
Explosion-proof type |
EXd II CT6 |
|
六、Application fields |
|
Desulphurization, denitration , etc.
Appendix
Reference table for corrosion resistance of transmitter diaphragm
☆ Good ○ Moderate × Bad
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