Selecting pressure transmitters for safety instrumented systems

This article deals specifically with the sensor portion of an SIS (safety instrumented system), addressing some of the techniques that can be used to improve the safety and reliability of field measurements. Of the various sensors available, the discussion focuses on differential pressure transmitters. This type predominates in the chemical process industries, being applicable for the measurement of pressure, differential pressure or flow, and liquid level. It employs a sensor to detect pressure changes, and, for remote transmissions, provides an electronic means of converting the pressure measurement into an aoppropriate signal in the 4-20-mA range.