• Selection of continuous sensors must include issues such as accuracy and resolution.
• Angular positions can be measured with potentiometers and encoders (more accurate).
• Tachometers are useful for measuring angular velocity.
• Linear positions can be measured with potentiometers (limited accuracy), LVDTs (limited range), moire fringes (high accuracy).
• Accelerometers measure acceleration of masses.
• Strain gauges and piezoelectric elements measure force.
• Pressure can be measured indirectly with bellows and Bourdon tubes.
• Flow rates can be measured with Venturi valves and pitot tubes.
• Temperatures can be measured with RTDs, thermocouples, and thermistors.
• Input signals can be single ended for more inputs or double ended for more accuracy.
Bryan, L.A. and Bryan, E.A., Programmable Controllers; Theory and Implementation, Industrial Text Co., 1988.
Swainston, F., A Systems Approach to Programmable Controllers, Delmar Publishers Inc., 1992.