1. Product overview of capacitive pressure transmitters.
I started to plan my 2024 AL1151 3351GP capacitive pressure transmitter key materials, components and parts and the whole machine after assembly and testing, the product has the characteristics of reasonable principle, complete varieties and specifications, easy installation and use. At the same time, it can be replaced with traditional 1151 and other well-known similar products, which has good versatility and replacement ability. In addition to being compact and exquisite, this series of products also has the HART fieldbus protocol and intelligent functions. 
The AL1151 3351GP pressure transmitter is used to measure the level, density and pressure of liquids, gases or vapors, which are then converted into 4 20mA DC signal outputs. The intelligent pressure transmitter can communicate with the HART communicator for setting, monitoring or on-site monitoring system with the host computer.
Second, the working principle of capacitive pressure transmitter.
AL1151 3351GP Capacitive Pressure Transmitter The process pressure is transmitted to the center of the D chamber through the isolation diaphragm and perfusive solution on both sides or one side. The central diaphragm is a tensioned elastic element, which produces a corresponding deformation displacement for the pressure difference between the two sides acting on it, and its displacement is proportional to the differential pressure, and the maximum displacement is about 01mm, this displacement transformation forms a differential capacitor on the capacitor plate, and the differential capacitor is converted into a two-wire 4 20mA DC signal output by the electronic circuit. (See photo).
The diagram above shows the basic working principle of a capacitive pressure transmitter, and the diagram below describes the functions of each component.
3. Product features of capacitive pressure transmitter.
Good accuracy. Good stability.
Two-wire system (special four-wire system).
Solid components, pluggable printed circuit boards.
Small, lightweight, strong and shock-resistant.
The measuring range and zero point are continuously adjustable externally.
Positive migration can reach 500%;Negative migration can reach 600%.
Adjustable damping. Good one-way overload protection characteristics.
There are no mechanical moving parts, and the maintenance workload is low.
The whole series has a unified structure and strong interchangeability of parts.
The diaphragm material in contact with the medium can be selected (316L, TAN, HAS-C, MONEL and other corrosion-resistant materials).
Explosion-proof structure, all-weather use.
Intelligent HART fieldbus protocol.
4. Functional parameters of capacitive pressure transmitter.
Objects to use: liquids, gases and vapors.
Measuring range: 0 01kpa to 0 40mpa
Output signal: 4 20mA DC (especially can be used for four-wire 220V power supply, 0 10mA DC output).
Power supply: 12 45V DC, generally 24V DC (see figure load characteristics).
Load characteristics: related to the power supply, the load capacity at a certain power supply voltage is shown in the above figure (load characteristics), the relationship between the load impedance RL and the power supply voltage VS is: RL 50 (VS-12).
Indication table: pointer linear indication 0 100% equal division scale or LCD liquid crystal type, LED digital tube display.
Explosion-proof: aFlameproof ExdiibT4 BT6, EXDIICT4 CT6, Dust Explosion-Proof: EXTEDA21 T80
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Measuring range and zero point: Externally continuously adjustable.
Positive and negative migration: After the zero point is positively migrated or negatively migrated, the absolute value of the measuring range, the upper and lower values of the measurement range cannot exceed 100% of the upper limit of the measurement range. (Intelligent: range ratio 15:1).
The maximum positive migration is 500% of the minimum trimming rangeThe maximum negative migration is 600% of the minimum trim range.
Temperature range: Amplifier operating temperature range: -29 93 (-25 70 for TL type).
Silicone-filled measuring cell: -40 104
When the flanged transmitter is filled with high-temperature silicone oil: -20 315, ordinary silicone oil: -40 149
Hydrostatic MPA
Humidity: Relative humidity is 0 100%.
Volume absorption: 016cm3
Damping (step response): When filled with silicone oil, it is generally 02s to 1Continuously adjustable between 67s.
Schematic diagram of external dimensions and installation connection (Note: This size is for reference only, and the actual product size shall prevail).
5. Selection method of capacitive pressure transmitter.
Pressure transmitter series products include: capacitive pressure transmitter;Diffusion silicon pressure transmitter;Stainless steel pressure transmitter;ceramic pressure transmitters, etc.