• Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or “broadcast” type of network. This means all data transmissions by all devices on a network are sensed by all the other devices. In other words, there are…

  • Layer 1 of the OSI Reference Model is where we define the “physical” elements of a digital data network. The H1 FF network exhibits the following properties: Two-wire (ungrounded) network cable 100 ohm (typical) characteristic impedance DC power is conveyed…

  • FOUNDATION Fieldbus is a standard for digital field instrumentation enabling field instruments to not only communicate with each other digitally, but also to execute all continuous control algorithms (such as PID, ratio control, cascade control, feedforward control, etc.) traditionally implemented in…

  • Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in 1979 for use in its industrial control products, Modbus is a protocol designed specifically for exchanging process data between industrial control devices. The Modbus standard does not specify any…

  • A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway Addressable Remote Transmitter. The purpose of the HART standard was to create a way for instruments to digitally communicate with one another over the same two wires used to convey…

  • At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication “connections” should be established between devices on a digital network. Rather than specifying addresses for routing data packets on a large network…

  • I remember first learning about the world-wide Internet, and wondering what it actually looked like. The first vision entering my mind when people told me about a computer network spanning nearly all of the United States and many other parts of…

  • An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research center in Palo Alto, California. His fundamental invention was the CSMA/CD method of channel arbitration, allowing multiple devices to share a common…

  • Some of the simplest types of digital communication networks found in industry are defined by the EIA (Electronic Industry Alliance) and TIA (Telecommunications Industry Alliance) groups, under the numerical labels 232, 422, and 485. This section discusses these three network…

  • One of the great benefits of digital technology is the ability to communicate vast amounts of information over networks. This very textbook you are reading was transmitted in digital form over the electronic network we call the Internet: a feat nearly impossible with…

  • Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly inexpensive as integrated circuits considering their capabilities. However, even the best ADC is useless in a real application unless the analog voltage signal input to it is properly conditioned, or “made…

  • In order to provide an interface between the internal (digital) world of a computer and the external (analog) world of process measurement and control, there must be some form of conversion taking place between these two types of data. Devices that generate…

  • Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent other types of data as well, such as alphabetical characters. The ability to encode non-numerical data in digital form is what allows computers to…

  • Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow through a pipe, the pressure of a fluid, etc. These data are all analog quantities: infinitely variable, not discrete. Discrete process measurements such as…

  • The advent of digital electronic circuitry has brought a steady stream of technological progress to industrial instrumentation. From early applications of digital computing in the 1960’s to the first distributed control systems (DCS) in the 1970’s to the “smart” transmitter…

Join 900+ subscribers

Stay in the loop with everything you need to know.

Sign up