I. product introduction
3351/1151DP capacitive differential pressure transmitter
The 3351 series of intelligent capacitive transmitters (hereinafter referred to as intelligent transmitters) are microprocessor based pressure meters, which have increased communication and other structures on the traditional 1151 capacitive transmitter. With 268 or 275 communicator or other host using HART protocol, two-way communication (read, write data and diagnosis) can be carried out at the control room, transmitter site or anywhere in the same control loop.

Two, main characteristics
The 3351 series of intelligent capacitive transmitters, besides the inherent characteristics of the general capacitive transmitter, also have the following characteristics:
Intelligent electronic components consist of only one component.
The range is 15:1 or 10:1.
0 0. 6 to 0 40 2000 km.
Local buttons adjust range and zeros.
It can update the existing TY-1151 (including 1151) all kinds of analog transmitters for intelligent instruments.
Conforming to the HART protocol, HART communicator 268 and 275 can be used for two-way communication with the smart meter without interrupting the output signal.
In the distributed control system using HART protocol, two-way communication with host computer is carried out.
It has the function of self diagnosis and remote diagnosis.
With EEPROM, no power failure, loss of data.

Three, working principle
The two pressure of the tested medium is passed into the high and low two pressure chambers, acting on the diaphragm on both sides of the delta element (that is, sensitive element). A capacitor is formed by measuring the electrodes on the diaphragm and the insulating sheets on both sides. When the pressure difference between two sides is inconsistent, the displacement of the measuring diaphragm is caused, and the displacement is directly proportional to the pressure difference. Therefore, the capacitance on both sides is not equal, and the signal is directly proportional to the pressure through the oscillation and demodulation links. The pressure transmitter and pressure transmitter have the same working principle as the differential pressure transmitter. The difference is that the low pressure chamber pressure is atmospheric pressure or vacuum. The converter converts the current of the demodulator into a digital signal, which is used by the microprocessor to determine the input pressure value. The microprocessor controls the work of the transmitter. In addition, it linearized the sensor. Reset the measurement range. Engineering unit conversion, damping, square root, sensor fine tuning and other operations, as well as diagnostic and digital communications.
This microprocessor has 16 byte program RAM, and has three 16 bit counters, one of which performs A /D conversion. The converter fine-tuning data from the microprocessor and calibrated digital signals, which can be modified by transmitter software. Data stored in EEPROM, even if the power is also intact. The digital communication line provides a connection interface between the transmitter and the external devices, such as type 275 intelligent communicator or HART protocol control system. This circuit detects the digital signal superimposed on the 4-20mA signal and transmits the required information through the loop. The type of communication is frequency shift keying FS technology and is based on BeII202 standard.
The capacitance transducer is composed of differential capacitance, and the input pressure is 0 ~ 40KPa.
0 ~ 250KPa and so on. Users: liquids, gases and vapors.

Four. Product selection