• 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.

22.4.1 References

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.