How to use HART 475 and 375 communicators?

What is HART Communicator?

HART is a bidirectional communication protocol that allows intelligent field instruments and host systems to exchange data. A host can be any software application, ranging from a technician’s handheld device or laptop to a plant’s process control, asset management, safety, or another system that employs any control platform. Communication takes place between two HART-enabled devices, which are often a smart field device and a control or monitoring system. Standard termination methods and instrumentation grade wiring ensure dependable communication.

HART supports two concurrent communication channels, one analog and one digital: A 4-20mA signal sends the primary measured value (PV) as an analog value of current via the instrument’s power cable. The current value is subsequently converted to a physical value by the host system using the parameters given by HART Software.

How Does HART Communicator Work?

HART is based on Bell 202 standards and operates on the frequent shift keying (FSK) principle. The digital HART signal has two frequencies: 1,200 Hz and 2,200 Hz. The signal at 1,200 Hz represents bit 1 and the frequency at 2,200 Hz represents bit 0. When sine waves of these frequencies superimpose on DC analog signal cables, data is transferred. Because the average value of an FSK signal is zero, the 4-20 mA signal is unaffected during this transfer. The HART protocol can generally communicate at 1200 bps without interfering with the 4-20mA signal. This allows the host application to get two or three digital updates from a smart device in a single second. The digital signals can contain any information, such as the device’s operational status, diagnostics, any measured value, and so on.

HART technology is distinguished as a master/slave protocol since the slave device (a smart device) operates only when linked to a master device (a computer or any other host device). The protocol is used in two modes, which are detailed in the next section.

Wireless HART technology, often known as Wireless HART, has grown in prominence over the years. This method eliminates the need for connection wires by utilizing a digital parameter range. It is the first wireless communication standard for industrial automation.

How to use HART 475 Communicator?

The 475 Field Communicator can configure, maintain, and troubleshoot HART and FOUNDATION Fieldbus devices. Follow all standards and procedures applicable to the location when using the 475 Field Communicator to communicate with devices.

Before starting the 475 Field Communicator, make sure it is not damaged, that the battery is fully seated, that all screws are properly tightened, and that the communication connections are free of dirt and debris.

To Start HART 475 Communicator

  1. Press and hold the Power button on the keypad until the green light blinks (approximately two seconds). During startup, the 475 Field Communicator tells you if a System Card upgrade is required. The Main Menu of the Field Communicator appears.

  2. Select an icon or menu item using the touch screen or the up and down arrow keys.

  3. To turn off the communicator, hit the Power button and then select Shut down from the Power Switch menu. Select OK.

To make communication with the computer applications

The 475 Field Communicator or its System Card can communicate with a PC via the IrDA interface, Bluetooth interface (if licensed), and a compatible card reader. The position of the IrDA interface and the System Card (Check the below image). Only the Easy Upgrade Utility can be used with a card reader. For more information, consult the 475 Field Communicator User’s Manual.

To make communication with the device

Connect the 475 Field Communicator to the loop, segment, or device using the included lead set. The 475 Field Communicator has three communication terminals for the lead set on top. Each red terminal represents a positive connection for its own protocol, whereas the black terminal represents a common terminal shared by both protocols. An access door keeps just one pair of terminals exposed at any given time. Several indications identify which terminal pair is for which protocol.

How to use HART 375 Communicator?

The HART 375 Communicator’s primary function is to communicate with an instrument that uses the HART protocol. Provide information about the instrument being reviewed. The identification covers the instrument type, sensor type, model number, and so on. We can name/tag each HART instrument in the plants.

To Start HART 375 Communicator

Hold down the on/off key until the Multifunction LED flashes to signify that the unit is powered on (approximately two seconds).

During starting, the 375-field communicator will load any software upgrades available on the system card automatically. When finished, the 375 Main Menu will be displayed. After powering on the 375 Field Communicator, you have the option of:

  • launching the HART or FOUNDATION Fieldbus applications
  • configuring/viewing settings; or listening for PC.
  • Start the ScratchPad application.

Shutting Down of HART 375 Communicator

The on/off key is disabled when applications are open. Before pressing the on/off key, you must first exit to the 375 Main Menu. To switch off the 375 Field Communicator, press and hold the on/off key for three seconds or until the display turns off.

To make communication with the computer

Infrared technology is used by the 375 Field Communicator to communicate with PCs. IrDA is the solely supported PC interface for transferring device descriptions, software updates, configurations, event captures, and ScratchPad files.

IrDA communication can be incorporated into the PC itself or given via an adapter such as a USB to IrDA adapter or a serial to IrDA adapter. For operational instructions, consult your IrDA manual.

Infrared transmissions with the 375 Field Communicator have a throughput of about 4 kilobytes per second. The suggested maximum distance between the IrDA and PC is 18 inches.

Listen For PC

In Listen for PC, the 375 Field Communicator is controlled by a PC application for data transfer and device configuration management. One of the following PC applications could be used:

The following are examples:

  • Emerson Process Management Advanced Management System (version) 6.2 or above), management software a process plant’s instrumentation and valves.
  • AMS currently only supports HART configurations.
  • Data were received via a 375 Field Communicator using the Field Communicator Programming Utility 375, PC-based software for transferring and receiving files.

To activate Listen for the PC mode, follow these steps:

  1. Select Listen for PC from the 375 Main Menu.

  2. Align the IrDA interface on the 375 Field Communicator with the IrDA interface for PC

  3. Use them to complete the necessary transfer(s).

  4. Select EXIT to exit the Listen for PC application.

The Internal Flash will be updated whenever new system software is downloaded to the 375 Field Communicator System Card.

Comparison between HART 375 and 475 communicators

HART 375 Vs 475

Parameters 375 Communicator 475 Communicator
Microprocessor 80 MHz Hitachi SH3 80 MHz Hitachi SH3
System Card 1 GB secure digital card 1 GB
RAM 32 MB 32 MB
Display 1/4 VGA (240 by 320 pixels) monochrome 3.8” (9.6 cm) transflective display with touch screen 1/4 VGA (240 by 320 pixels) color, 3.5 in. (8.9 cm) transflective display with touch screen Anti-glare coated
Keypad 25 keys (including 4 action keys) 25 keys including 4 action keys, 12 alphanumeric keys, tab key, function key, backlight key, power key, and 4 cursor-control (arrow) keys;
Operating temperature 0°C to + 40°C 10°C to +40°C
Enclosure Rating IP51 IP51