User:AliceCybernetics/sandbox/Transmitter (engineering)

Transmitters are measuring instruments that are designed to resist the harsh environments that prevail in the process industries. They are widely used on petrochemical plant, mining, primary metals industries and water treatment plant. In other industries, measuring instruments may be referred to as sensors or transducers.

Design and construction
Transmitters are mechanically robust, will tolerate extremes of temperature, dust, water and chemicals. Versions are available that meet additional criteria such as safety in flammable atmospheres, machine safety and functional safety.

Transmitters provide continuous measurement of process variables. Devices that provide an on/off function rather than a continuous measurement are referred to as process switches, for example a pressure switch.

Electrical connections
Electrical connections are designed for electromagnetic compatibility (to resist to electrical interference) and the signals are standardized to simplify integration into plant control systems. Popular variants are:
 * "analog 4-20mA" a robust scheme that supplies power to the instrument as well as the measurement and status data
 * "fieldbus" a multi drop digital network for
 * "wireless" typically a wireless version of fieldbus or Ethernet, power provided by a long life battery

Process connections
Process connections (the means of connecting the instrument to the plant for example to measure pressure or flow in a vessel) are standardized in popular sizes of pipe threads or flanges)

Installation
The traditional method of mounting instruments is by pipe clamp onto a 2 inch 50mm diameter pipe. Bulkhead (wall) mounting models are available.

Differential pressure transmitters are generally mounted on a manifold that incorporates valves to allow isolation and testing to be carried out safely, with minimum waste of process fluid.

Engineering
The branch of engineering concerned with transmitters and their application in process applications is control and instrumentation (C&I). Principles are set out in major works by and. Standards applicable to C&I engineering are set by ISA, EN and BS and cover good practice in design, installation , safety in flammable atmospheres and functional safety.