2.6 Selection of Sensing Devices

A number of factors must be considered before a specific means of measuring the process variable (PV) can be selected for a particular loop:

• The normal range over which the PV may vary, and if there are any extremes to this

• The accuracy, precision and sensitivity required for the measurement

• The sensor dynamics required

• The reliability that is required

• The costs involved, including installation and operating costs as well as purchase costs

• The installation requirements and problems, such as size and shape restraints, remote transmission, corrosive fluids, explosive mixtures, etc.