Components of WirelessHART Technology

The gateway provides a connection to the host network, from WirelessHART to the main host interface, such as Modbus bus, fieldbus (Profibus), or Ethernet. The gateway also provides a network manager and a security manager (these features can also exist at the host level-but initially they will be on the gateway.

The network manager establishes and maintains a MESH network. It determines the best path and manages the allocation of time slice access (WirelessHART divides each second into 10 millisecond time slices). Time slice access depends on the required process value refresh rate and other access (alarm-configuration changes).

The security manager manages and assigns security encryption keys. It also keeps a list of devices authorized to join the network.

The process includes measuring equipment-instruments with HART functions.

A repeater is a device that routes WirelessHART messages, but may not have its own process connection. Its main role will be to expand the scope of the WirelessHART network, or to help "bypass" existing or new obstacles. All instruments in WirelessHART network have routing function, which simplifies the planning and implementation of wireless network.

 An adapter is a device that plugs into an existing instrument with HART function and transmits instrument data to the host through the WirelessHART network. The adapter can be located anywhere on the instrument's 4-20mA cable; it can be powered by a battery or powered from a 4-20mA cable. Some adapters will be powered by batteries and will also use the same battery to power the instrument. In this case, there is no longer a 4-20mA signal to the host-all process data will be reported through WirelessHART.

There are two versions of handheld terminals. In the first case, the handheld will be a standard HART FSK configuration unit (only adding DD or DOF files for new devices), just like routine tasks such as routine maintenance and calibration checks. In the case of wireless support, handheld is used to add new instruments to the existing WirelessHART network.

In the second case, the hand holds a WirelessHART connection to the gateway and then to the instrument, which can be used to read process variables (PV) or for diagnostic purposes.