The high accuracy offered by HART transmitters is used to its maximum potential when the process variables are transmitted in digital form from the field instrument through the I/O to the controlling host. The controller can access the status of each smart field device, providing greater diagnostic information on the health and operation of the associated sensor.
MTL8000 Process I/O system has been designed to be transparent to HART signals, thus allowing the host control software and any field instruments to communicate directly with each other.
Process I/O™ uses MTL8000 Series AI and AO with HART modules to regularly scan up to four HART process and device status variables. These are accessible to the controller via the Modbus or Profibus link and the control system can be configured to use this important data to improve overall process control.
For HART valve positioners, the travel of the control valve dictated by the 4–20mA drive signal can be monitored by the controller as one of the HART process variables, allowing the valve position to be displayed on the HMI face plate.
For Zone 2 applications the MTL8000 -2/x series modular I/O system provides direct communication with the controller via an open bus to an I/O ‘node’ located close to field instruments often in harsh and hazardous environments.