3151SL Level Transmitter

Level measurement accuracy up to 0.15%
Calibrated span from 3.74 kPa to 2068 kPa
Flat diaphragm type, with 2, 4, and 6-inch extended diaphragms
Multiple fill fluids available to meet different application requirements
Wetted parts materials: stainless steel, Hastelloy, and tantalum

Working Principle
The measured pressure is converted into a capacitance variable by the capacitive sensing element, which is then directly converted into a digital signal via an A/D circuit. The converted signal is sent to the microprocessor, where the digitally processed signal is further converted by a D/A converter into a 4–20 mA DC output signal for transmission to display/regulating instruments or DCS systems. The communication line converts the digital measurement pressure signal from the microprocessor into a frequency signal and superimposes it onto the 4–20 mA DC analog signal, which is received by the corresponding HART terminal device.

Features
· High stability and reliability
The highly sensitive pressure sensing element is fully sealed, with stress isolation structure and overpressure self-protection to ensure stability and reliability.
· Automatic compensation function
EEPROM stores pressure and temperature correction coefficients for automatic linear and temperature compensation by the main control unit microprocessor, ensuring high accuracy and minimal temperature influence for the 3151 smart transmitter.
· Digital communication and data storage
HART hand communicator enables remote configuration, monitoring, and diagnostics. Configuration data is stored in the non-volatile EEPROM on the circuit board and remains intact after power loss. The transmitter resumes operation immediately upon power restoration.
· Five-digit LCD output display
The five-digit LCD indicator displays digital readings of measured pressure (including engineering units such as kPa, kgf/cm2, mbar, mmH?O, etc.), percentage of span (%), and output current (mA).
· Configuration protection
A protection switch locks stored data to prevent unauthorized changes to the transmitter’s configuration.
· Local zero and span adjustment
The S and Z buttons on the main control unit allow users to adjust the transmitter’s zero and span without configuration tools.
· Explosion-proof certification
The transmitter’s explosion-proof models include intrinsic safety (Ex ia IIC T5) and flameproof (Ex d IIC T5), both certified according to national explosion-proof standards.
· High interchangeability of components
Regardless of span or output type, flanges, connections, electrical housings, display heads, end caps, and mounting brackets are interchangeable. Smart circuit boards are also interchangeable, though zero and span must be reset after replacement. Sensors are interchangeable and can be replaced to change the measurement range, but recalibration is required after replacement.

Software Functions
Using the 3151 configuration software and HART modem provided by Xiyi, users can perform testing, configuration, and fine-tuning on a computer. Alternatively, HART communicators can be used to access software functions.
· Testing
The 3151 transmitter continuously performs self-tests during operation. To test the 4–20 mA DC loop, the transmitter can be set to constant current output mode.
Configurable data includes: 4–20 mA points, engineering units, damping time, output mode (linear or square root), and related management information.
· Self-diagnostics
Diagnostic content includes: sensing element failure, A/D conversion failure, memory failure, and communication errors.
· Configuration tools
PC configuration tool
HART communicator.