ABB M4A-AT

Technical Specifications

1. Measurement Principle: Hydrostatic pressure liquid level detection
2. Standard Output Signal: 4–20mA DC two-wire loop signal; corresponding 0–100% full measurement range
3. Power Supply: Loop-powered 12VDC ~ 36VDC; minimum operating voltage 12VDC at maximum 20mA output
4. Measurement Accuracy: ±0.1% full scale; repeatability ±0.05% full scale
5. Response Time: ≤200ms adjustable via on-site parameter configuration
6. Ambient Operating Temperature: -20°C ~ +85°C; process medium temperature -40°C ~ +120°C
7. Humidity Tolerance: 0%–95% relative humidity non-condensing
8. Protection Grade: Enclosure front panel IP65; sensor probe IP68
9. Process Connection Standard: Optional NPT ½”, G½”, ISO 2852 sanitary flange thread interfaces
10. Communication Protocol Support: Modbus RTU RS-485 digital communication (optional expansion board)

Function Features

1. Integrated local LCD digital display with 3 physical operation buttons for zero-point calibration, range setting and unit switching without external configuration tools
2. Built-in full temperature automatic compensation circuit eliminates measurement deviation caused by medium and ambient temperature fluctuation
3. Configurable upper/lower limit alarm threshold with independent transistor switch output for high/low liquid level interlock protection
4. Overpressure and reverse power supply hardware protection circuit prevents sensor diaphragm and internal circuit damage
5. Onboard EMC surge suppression components for stable operation near high-power motors and frequency converters
6. Factory pre-calibrated with user-resettable factory default parameter storage function

Performance Parameters

• Long-term stability drift: <0.03% full scale per year without regular recalibration
• Maximum withstand overpressure: 200% full measurement range without permanent sensor deformation
• Analog output linearity error: ≤0.08% across full measuring span
• EMC Certification: IEC 61000-6-3 industrial process standard

Material Composition

1. Main Enclosure: Die-cast aluminum alloy with anti-corrosion polyurethane coating
2. Sensing Diaphragm: 316L stainless steel standard; Hastelloy C276 optional for corrosive chemical media
3. Internal Circuit Substrate: FR-4 high-temperature PCB with moisture-proof conformal coating
4. Display Window: Tempered anti-scratch transparent glass
5. Process Connection Fitting: 316L stainless steel threaded/flange joint

Structural Features

1. Split integrated structure: Upper display control housing separable from lower pressure sensing probe assembly
2. Rotatable 330° display housing for flexible on-site viewing angle adjustment regardless of installation orientation
3. Sealed cable gland interface for armored field signal cable entry, water and dust intrusion prevention
4. Internal circuit module fully sealed with silicone potting compound to resist condensation and chemical vapor corrosion
5. Detachable terminal wiring compartment cover for convenient two-wire loop wiring operation

Working Principle

1. Liquid medium height generates hydrostatic pressure acting on the stainless steel sensing diaphragm
2. Internal piezoresistive Wheatstone bridge converts pressure variation into tiny resistance difference electrical signal
3. Signal amplification, temperature compensation and linear correction circuit processes raw sensing signal into standard 4–20mA analog output
4. Local LCD module reads real-time internal digital measurement value and displays liquid level height percentage or engineering unit value
5. On-board logic chip compares measured value with user-configured alarm threshold to trigger external switch interlock signal when exceeding set limit

Advantage Highlights

1. Ultra-high ±0.1% full-scale measurement accuracy meets pharmaceutical, food and fine chemical precision tank batching requirements
2. Two-wire loop power supply simplifies field wiring layout, eliminating separate power cable laying for transmitters
3. Rotatable display housing adapts to vertical, horizontal and side-mounted installation modes without visibility obstruction
4. Optional Hastelloy sensing diaphragm compatible with strong acid, alkali and chloride-containing corrosive liquid media
5. Wide temperature operating range supports outdoor tank installation without additional thermal insulation housing

Applicable Industries

Installation Requirements

1. Mount vertically downward on tank side wall or top flange; horizontal probe installation strictly prohibited to avoid measurement zero drift
2. Signal cable adopts shielded twisted pair wire; shielding layer single-point grounded at DCS control cabinet terminal bar
3. Process connection thread coated with PTFE sealing tape to prevent medium leakage at joint
4. Maintain minimum 10cm distance between transmitter housing and high-power inverter/motor equipment to reduce electromagnetic interference
5. Install drainage valve below sensing probe for regular medium sediment cleaning without dismounting transmitter

Usage Notes

1. Strictly avoid medium solid particle sediment accumulation on sensing diaphragm; flush diaphragm regularly if measuring slurry liquid
2. Do not apply torque exceeding 25 N·m on process thread connection to prevent thread cracking and diaphragm deformation
3. Calibrate zero point monthly if measuring medium temperature fluctuation exceeds ±30°C
4. Prohibit immersion of upper display housing in liquid medium; only lower sensing probe supports IP68 submergence
5. Disconnect loop power supply before opening wiring compartment cover for wiring maintenance