Transducers

Interfacing Transducers to Electronic Control and

Measuring Systems

Raj Kamal [2012EEC01]

Sudhakar Kumar [2012EEC02]

Abhishek Chauhan [2012EEC03]

Shubham Kumar Pandey [2012EEC04]

What is a transducer?• A device, which when actuated by energy in one

transmission system, supplies energy in the sameform or in another form to a second transmissionsystem.

• The non-electrical quantity is converted into anelectrical signal.

Parameters

Linearity

Sensitivity

Dynamic Range

Repeatability

Physical Size

Classification of Transducers

Basis of Application

Potentiometric Device (Pressure, Displacement).

Methods of Energy Conversion

Hall Effect Pick Up, Ionization Chamber.

Nature of the Output Signal

Need of Interfacing Transducers Output voltages and currents from many transducers

are very small signals.

The transducer output is needed to be transmitted upto some distance.

Electrical Noise can pose problems.

Selecting a Transducer Operating Range

Frequency Response and Resonant Frequency

Environmental Capability

Minimum Sensitivity and Sensitivity

Accuracy

Usage and Ruggedness

Electrical Parameters

Combating Noise To increase the strength of low level signals before

transmission through the wires.

Done with the help of an Instrumentation Amplifier.

Instrumentation Amplifier Finite gain

High impedance

differential input

High Common-mode

voltage range

High Common-mode

rejection (90 dB)

Noise Effect The connections to the transducer should be

differential to prevent the introduction the noise.

Use of Isolation Amplifiers where the noiseenvironment is so severe that conventional amplifierscan’t survive the signal levels encountered.

Sources of Error These errors occur when transmitting a low-level

signal to any significant distance.

A method of reducing errors due to interveningresistances and the effect of power supply currents is touse current rather than voltages for transmission.

Voltage-to-Frequency Converter An Integrator that feeds a comparator, which in turn

drives a one-shot multivibrator. An electronic switchdischarges the integrator via a current source.

The major reason for converting a voltage to afrequency is so that an analog signal can betransmitted through a communication system,whether it be wires or some more sophisticatedsystem.

IEEE Standards IEEE 1451 is a set of smart transducer interface

standards for connecting transducers (sensors or actuators) to microprocessors, instrumentation systems, and control/field networks.