One product overview
ZY-3351DP Capacitive Differential Pressure Transmitter
The 3351 series intelligent capacitive transmitter (hereinafter referred to as the intelligent transmitter) is a pressure instrument with a microprocessor as its core. It adds communication and other functions to the structure of the traditional 1151 capacitive transmitter. The 268, 275 communicator or other host using the HART protocol can be used for bidirectional communication (reading, writing data, and diagnostics) with it in the control room, transmitter site, or anywhere within the same control loop.

II main features
In addition to the inherent characteristics of general capacitive transmitters, the 3351 series intelligent capacitive transmitter also has the following features:
·Intelligent electronic components are composed of only one piece.
·Range ratio of 15:1 or 10:1.
·0-0.6-0-42000KPa.
·Adjust the range and zero point locally by pressing the button.
·The existing TY-1151 (including 1151) various analog transmitters can be updated as smart instruments.
·Compliant with the HART protocol, the HART communicator 268 and 275 can be used for bidirectional communication with this smart meter without interrupting the output signal.
·Bidirectional communication with the host in a distributed control system using the HART protocol.
·It has self diagnostic and remote diagnostic functions.
·Equipped with EEPROM, not afraid of losing data due to power failure.

III Working principle
The two pressures of the measured medium are introduced into the high and low pressure chambers, acting on the isolation diaphragms on both sides of the δ element (i.e. sensitive element), and transmitted to both sides of the measuring diaphragm through the isolation diaphragms and the filling liquid inside the element. Measure the electrodes on both sides of the diaphragm and insulating film to form a capacitor. When the pressure on both sides is not consistent, it causes displacement of the measuring diaphragm, which is proportional to the pressure difference. Therefore, the capacitance on both sides is unequal. Through oscillation and demodulation, it is converted into a signal proportional to the pressure. The working principle of pressure transmitters and positive pressure transmitters is the same as that of differential pressure transmitters, except that the pressure in the low-pressure chamber is atmospheric pressure or vacuum. The converter converts the current of the demodulator into a digital signal, and its value is used by the microprocessor to determine the input pressure value. The microprocessor controls the operation of the transmitter. Additionally, it linearizes the sensor. Reset the measurement range. Engineering unit conversion, damping, square root, sensor fine-tuning and other calculations, as well as diagnosis and digital communication.
This microprocessor has 16 byte program RAM and three 16 bit counters, one of which performs A/D conversion. The converter fine tunes the digital signals from the microprocessor that have been calibrated, and these data can be modified using transmitter software. The data is stored in EEPROM and remains intact even when powered off. The digital communication line provides a connection interface for the transmitter to external devices such as the 275 smart communicator or control systems using the HART protocol. This circuit detects the digital signal superimposed on the 4-20mA signal and transmits the required information through the circuit. The type of communication is frequency shift keying (FS) technology and is based on the BeII202 standard.
A capacitive transmitter is composed of differential capacitance as the detection principle, with input pressures ranging from 0 to 40KPa,
0-250KPa, etc. Target audience: liquids, gases, and vapors.

1. Adopting the principle of capacitive differential pressure measurement, the accuracy is more than 10 times that of ordinary cores

2. IP65 protection level, non-destructive testing, salt spray testing, dustproof, anti spray

3. Adopting 316L cast steel material and high-precision stainless steel structure, achieving all solid state design

4. 8ms fast response, achieving zero error

5. Standard three wire terminal block, easy to connect, securely installed, and stable in measurement performance

6. New impact and lightning protection device added to achieve 24-hour protection