In the the process control industry, standardized communication protocols are employed to enable devices made by different manufacturers to communicate with one another in an easy to use and implement manner. One communication standard used in the process control industry is the Highway Addressable Remote Transmitter (HART) communication protocol, referred to generally as the HART protocol. Generally speaking, the HART protocol supports a combined digital and analog signal on a dedicated wire or set of wires, in which online process signals (e.g., such as control signals, sensor measurements, etc.) are provided as an analog current signal (e.g., ranging from 4 to 20 milliamps) and in which other signals, such as device data, requests for device data, configuration data, alarm and event data, etc., are provided as digital signals superimposed or multiplexed onto the same wire or set of wires as the analog signal. However, the HART protocol currently requires the use of dedicated, hardwired communication lines, resulting in significant wiring needs within a process plant.
The Wired Highway Addressable Remote Transducer (Wired HART) protocol is a backward-compatible enhancement to 4-20 mA instrumentation that allows two-way communications with smart, microprocessor-based field devices. More specifically, the Wired HART protocol is a digital industrial automation protocol that makes use of the Bell 202 Frequency-Shift Keying (FSK) standard to superimpose digital communications signals at a low level on top of the 4-20 mA signals for communications over legacy 4-20 mA analog instrumentation wiring. Communications based on the Wired HART protocol occurs between any two Wired HART-enabled devices, typically a smart field device and a control or monitoring system. Communications occurs using standard instrumentation grade wire and using standard wiring and termination practices. As the Wired HART protocol is a master/slave protocol, a smart field device (i.e., the slave) only speaks when spoken to by a master device application (i.e., the master). A number of tasks can be achieved when a master device communicates with smart field devices, including: device configuration or re-configuration, device diagnostics, device troubleshooting, reading additional measurement values, obtaining device health and status, and so on.
The Wired HART protocol provides two simultaneous communications channels: the 4-20 mA analog signal and a digital signal. The 4-20 mA signal is used for communications of the primary measured value by field smart devices using the 4-20 mA current loop. The digital signal, superimposed on the 4-20 mA analog signal, contains information from the smart field device including device status, diagnostics, additional measured or calculated values, etc.
The WirelessHART (also referred to as wireless HART) protocol is a wireless mesh network communications protocol for process automation applications, and adds wireless capabilities to the Wired HART protocol while maintaining compatibility with existing Wired HART-enabled devices, commands and tools. A WirelessHART network uses IEEE 802.15.4 compatible radios operating in the 2.4 GHz radio band. Each device in the WirelessHART mesh network can serve as a router for messages from other devices. In other words, a device does not have to communicate directly to a gateway, but just forward its message to the next closest devices. This extends the range of the WirelessHART network and provides redundant communications routes to increase reliability.
A typical WirelessHART device requires a 2-byte Network ID and a 16-byte Join key to join a WirelessHART network. This information is provided to WirelessHART devices through the wired HART interface. The majority of factory produced WirelessHART devices are configured with a manufacturer default assigned Network ID and Join key. Thus, an installer requires a proper system and tool to provide a WirelessHART device to join an existing wireless network through a 2-wire HART interface connection present on the device.
One example is a thumb adapter requiring a physical HART modem connection to a PC where AMS is running (or a HC-475 handheld device) to connect to THUM and enter a customer Network ID and Join key manually into THUM to join the customer installed wireless network. Another example is SKF WirelessHART Vibration device model CMWA 8800. This does not even have a 2-wire HART Modem interface, and therefore a user needs to execute some key pattern to allow the device to go to a known default network ID and join keys. To change these settings, a temporary gateway is required to provision this device to join a customer installed target network.
Some organizations and companies support multi-protocol wireless solutions. Thus, a customer has to buy multiple provisioning tools (e.g., SKF vibration tool where no physical connection is available with the device) for specific vendor devices, which is very costly and difficult to maintain. In addition, transmitters may be installed in hazardous locations (e.g., such as industrial plants) or where the configuration (e.g., a physical connection device enclosure should be opened for WirelessHART provisioning) is not allowed due to on site customer safety regulations.