EATON MTL4850 HART multiplexer complete guide

Eaton MTL4850 HART multiplexer: the core hub for intelligent field device management

System Overview

1.1 System Functions and Positioning

The MTL4850 HART maintenance system enables users to calibrate, configure, and maintain intelligent field devices for the entire network from a single workstation. The core of the system is the MTL4850 module, which provides multiplexing functionality for various field devices, allowing each device to be addressed and recognized from the workstation.

Another important component of the system is the terminal circuit board, which simplifies the interconnection of field devices to the MTL4850 module. MTL offers a range of terminal boards and backplates to meet most general application needs, as well as customized versions for specific OEM and application designs.

1.2 System Capacity and Scalability

One MTL4850 HART multiplexer module can accommodate up to 32 field devices. These modules are connected to a PC running HART maintenance software through an RS485 to USB (or Ethernet) converter. Depending on the management software, up to 63 MTL4850 modules can be connected to a serial link, which means a single system can support up to 2016 smart field devices.

Detailed explanation of system components

The MTL4850 system adopts a modular design and provides multiple connection solutions based on application requirements and on-site explosion-proof levels.

2.1 Core module: MTL4850 multiplexer

The MTL4850 module is the core of the system and adopts a plug-in design, firmly installed on the backplane through fixing screws. There is an LED indicator light at the top of the module for status indication:

PWR (green): Power indicator

Fault (red): Fault indication, flashing mode indicates different states (such as establishing scan list, not finding HART loop, detected fault, etc.)

HOST (yellow): Host communication indicator

HART (yellow): HART communication indicator

2.2 Connecting units and interfaces

2.2.1 HTP-SC32 Integrated Connection Unit

HTP-SC32 is a 32 channel integrated solution with an onboard MTL4850 multiplexer, suitable for non explosion proof areas (safe zones). It uses screw clamp terminals to connect on-site equipment and systems, with each channel isolated and capable of connecting two-wire transmitters, 4-20mA current circuits, or voltage inputs. The HART signal requires an impedance of>240 Ω to be connected, and the board has reserved a position for installing parallel resistors (usually 250 Ω) or series resistors.

Installation: Suitable for T-shaped or G-type DIN rails, can be installed in any direction. The weight of the carrier board is 500g, and the weight of the module is 120g.

Power supply: Redundant 24V DC input, connected through pluggable 4-position screw terminals. The LED indicates the power status. Power consumption: 75mA @ 24V DC.

RS485 communication: Two RS485 ports are provided for connecting the upper computer PC and cascading other HART interface devices.

HART address setting: Set the unique HART address of MTL4850 using binary encoding through the 6-digit DIP switch (SW1) on the board.

2.2.2 HMP-HM64 HART Interface

HMP-HM64 is a compact interface used to connect connection units and maintenance systems. It can accommodate two MTL4850 modules, support 64 channels, and can cascade more modules through RS485.

Connection: Receive HART signals from HCU16 or HCU16AO connection units through four 20 way flat cable connectors (P1-P4). P1/P2 connection module 1, P3/P4 connection module 2.

Installation: DIN rail installation, with a weight of 230g for the carrier board and 120g for each module.

Power supply: redundant 24V DC, power consumption 130mA @ 24V DC (dual module).

Address setting: Set two MTL4850 addresses using a 5-digit DIP switch (SW1). HMP-HM64 can only set even addresses (0, 2, 4, 8, 16, 32). Module 1 uses this even address, and module 2 automatically uses the next odd address.

2.2.3 HCU16 HART Connection Unit

HCU16 provides on-site wiring to the host/system control interface for non explosion proof areas, and also provides a HART signal outlet for maintenance systems. Each channel has three terminals:+ve, - ve, and transmitter power supply terminal (Tx+).

Installation: DIN rail installation, carrier weight 330g, height 53mm.

Connection: Connect to HMP-HM64 through a 20 way flat cable connector.

2.2.4 HCU16AO HART Connection Unit (for Analog Output)

The 4-20mA analog output impedance of many systems is too low to transmit HART signals properly, and output noise may interfere with HART data. HCU16AO is designed specifically to solve this problem, with 16 isolated channels, each of which is connected in series with a low-pass filter in the current signal from the system. This filter has almost no effect on 4-20mA signals, but presents a high impedance of>240 Ω for HART signals, making it easy to detect and measure.

Installation: DIN rail installation, carrier weight 770g, height 58mm.

Connection: The on-site and system connections are completed through pluggable 8-bit screw terminals (4 sets, 4 channels per set). Connect to HMP-HM64 via 20 flat cables.

2.3 Intrinsic Safety (IS) Application Backboard