EMI502 - Resistive Transducers

Electronic Measurements & Instrumentation (EMI) Unit-5 : Transducers EMI502 - Resistive Transducers Resistive transducers are those in which the resistance changes due to a change in some physical phenomenon. The change in the value of the resistance with a change in the length of the conductor can be used to measure displacement. Strain gauges work on the principle that the resistance of a conductor or semiconductor changes when strained. This can be used for the measurement of displacement, force and pressure. Resistive transducers are those in which the resistance changes due to a change in some physical phenomenon. The change in the value of the resistance with a change in the length of the conductor can be used to measure displacement. Strain gauges work on the principle that the resistance of a conductor or semiconductor changes when strained. This can be used for the measurement of displacement, force and pressure. The resistivity of materials changes with changes in temperature. This property can be used for the measurement of temperature. Potentiometer Resistance Pressure Transducer Advantage of Potentiometers They are inexpensive. Simple to operate and are very useful for applications where the requirements are not particularly severe. They are useful for the measurement of large amplitudes of displacement. Electrical efficiency is very high, and they provide sufficient output to allow control operations. Disadvantages of Potentiometers When using a linear potentiometer, a large force is required to move the sliding contacts. The sliding contacts can wear out, become misaligned and generate noise. Resistance Pressure Transducer Measurement in the resistive type of transducer is based on the fact that a change in pressure results in a resistance change in the sensing elements. Resistance pressure transducers are of two main types. First, the electromechanical resistance transducer, in which a change of pressure, stress, position, displacement or other mechanical variation is applied to a variable resistor. Second, is the strain gauge, where the stress acts directly on the resistance. It is very commonly used for stress and displacement measurement in instrumentation. This resistance change can be made part of a bridge circuit and then taken as either ac or dc output signal to determine the pressure indication.