Remote Process Control Measurement / Modbus TCP

Oil companies, mining companies, public water, electrical and gas utilities all have some form of automated industrial measurement and process control application to provide better management of automated processes.

These processes usually need to be monitored remotely, hence there is a requirement to have sensor and process data read electronically on site and then transferred to a central system or control room where staff can view the readings and make decisions about the operation of or perhaps the shutdown of functions at a remote site.

Application Detail

A typical remote site may have industrial pressure / temperature sensors monitoring key points in a remote pumping station / oil well/ as pipeline. In a remote pumping station, it is likely that a local industrial Remote Terminal Unit (RTU) would be providing local control to several processes as well as providing the capability to connect via Modbus to a central Supervision Control and Data Acquisition (SCADA) system.

Most RTUs have the industry standard Modbus interface. Modbus is a serial communication protocol that is used to establish master / slave communication between devices. Master / slave communication is a type of data transfer where only master can send request to slave to perform the action and send response back to master. There is no way for the field device acting as a slave to initiate communication.

Unidata can provide the Neon Remote System that can be set up so that:
• Neon Remote Logger and Neon Server act as Modbus Master that collects and presents Modbus Slaves’ data or
• Neon Remote Server act as Modbus Slave that presents data as Modbus TCP for SCADA Modbus Master ingestion.

Unidata Neon Remote Loggers can connect to the Modbus interface of most RTU equipment and can extract status and readings information on a routine basis, say every 5, 10 or 30 minute basis and transmit that data across a cell phone and / or a satellite network to central Neon Server.

The collected data, status points and instrument readings are then stored and displayed on the Neon Server. Using a standard web browser, data can be accessed from anywhere on the Internet using a standard web browser. Subject to Health, Safety and Security Regulation requirements, limited control functions can be initiated across the link, for example remote shutdown.

There are some typical application scenarios detailed here.

The first application example shows specific pressure and temperature sensors being read via standard industrial Modbus inputs. In this configuration pressure and temperature sensors are modbus slaves while the Neon Remote Logger acts as modbus master. The data is available for reporting out by ftp, web services and a specific SQL database view.

A second application shows a typical (for example Emerson ROC) RTU data being collected by the Neon Remote Logger (slave), then being passed to the Neon Server which acts as Modbus TCP interface to (master) central SCADA system. The data is available for reporting out by ftp, web services and a specific SQL database view.