Description
NMTU-21C: Product Overview
This module operates within the signal conditioning layer of industrial automation systems, positioned between field temperature sensors (e.g., RTDs, thermocouples) and control systems (DCS, PLC). Its role is to amplify, linearize, and convert low-level sensor signals into standardized 4-20mA analog outputs or HART protocol data for process monitoring and control. In a typical architecture, it mounts in field junction boxes or control cabinets, interfacing with ABB 800xA DCS or AC500 PLCs via analog input modules.
Core functionality includes supporting multiple sensor types (Pt100/Pt1000 RTDs, J/K/T thermocouples), performing cold-junction compensation for thermocouples, and providing galvanic isolation (2.5kV RMS) between field circuits and control systems to prevent ground loop interference. It embeds HART 7 protocol for bidirectional communication (device configuration, diagnostics) superimposed on the 4-20mA signal, and integrates with ABB’s Asset Management tools for remote monitoring of sensor health (e.g., drift, calibration status).
The module belongs to the ABB Measurement Series, a platform optimized for process instrumentation integration. Benefits of this series include modular design for flexible sensor compatibility, compliance with IEC 60751 (RTD) and IEC 60584 (thermocouple) standards for accuracy, and hot-swappable components to minimize downtime during maintenance. This series streamlines upgrades by allowing incremental replacement of legacy transmitters without reconfiguring the entire control system.
ABB NMTU-21C
NMTU-21C: Technical Specifications
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Model Number: NMTU-21C
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Manufacturer: ABB Ltd.
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Product Type: Temperature/Universal Signal Transmitter Module
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Supported Sensors: Pt100, Pt1000 (RTD); J, K, T (thermocouple)
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Input Signal Range: -200°C to +850°C (RTD); -270°C to +1370°C (thermocouple)
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Accuracy: ±0.1% of full scale (at 25°C), ±0.2% over operating range
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Output Signal: 4-20mA DC (active/passive mode), HART 7 (superimposed)
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Isolation Voltage: 2.5kV RMS (input-to-output, input-to-power)
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Cold-Junction Compensation: Automatic (for thermocouples, ±1°C accuracy)
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Power Supply: 24V DC (±10%, 1.2W max)
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Operating Temperature: -40°C to +85°C (module); -50°C to +100°C (sensor loop)
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Protection Rating: IP65 (field housing), IP20 (panel mount)
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Dimensions: 100mm (H) x 50mm (W) x 75mm (D) (field housing)
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Weight: ~0.5kg (field housing)
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Certifications: CE, UL (cULus Listed), RoHS, ATEX Zone 1/2 (optional)
Core Features & Customer Value
Support for multiple sensor types (RTD/thermocouple) eliminates the need for separate transmitters in mixed-measurement applications, simplifying inventory and panel design. For engineers, this reduces engineering time during retrofits—e.g., upgrading a chemical reactor’s temperature monitoring from legacy RTDs to thermocouples without replacing the entire signal chain. The ±0.1% accuracy ensures precise process control, critical for applications like pharmaceutical sterilization where ±1°C deviation can compromise sterility.
HART 7 protocol enables remote configuration (e.g., range adjustment, sensor trim) and retrieval of diagnostic data (e.g., sensor resistance, ambient temperature) without interrupting the 4-20mA signal. For maintenance teams, this reduces field visits by 50% in remote facilities like offshore oil platforms. Galvanic isolation (2.5kV RMS) protects control systems from voltage transients induced by nearby motor drives, minimizing controller damage risk in steel mills or mining operations.
The module’s wide operating temperature range (-40°C to +85°C) supports deployment in unconditioned environments, such as outdoor pipeline monitoring stations or cryogenic storage tanks. Hot-swappable design (with redundant power) permits replacement during operation in 24/7 facilities like power plants, reducing downtime from hours to minutes.
ABB NMTU-21C
Typical Applications
In a chemical distillation column, the module interfaces with Pt100 RTDs on tray temperatures, transmitting 4-20mA signals to an ABB 800xA DCS for reflux ratio control. HART diagnostics monitor sensor drift, alerting operators to calibrate before accuracy degrades beyond ±0.5%.
At a municipal waste incinerator, it processes K-type thermocouple signals from flue gas temperatures, with cold-junction compensation ensuring accuracy despite ambient heat. The IP65 housing resists dust and moisture in the non-climate-controlled control room.
In a food processing plant, the module monitors T-type thermocouples in a pasteurization tunnel, maintaining 72°C for 15 seconds. The 4-20mA output adjusts steam valve positions via a PID loop, with HART logging cycle counts for maintenance scheduling.
