Electronic Measurement & Instrumentation

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 same form or in another form to a second transmission system.

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

ParametersLinearity

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 TransducersOutput 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 TransducerOperating RangeFrequency Response and Resonant

FrequencyEnvironmental CapabilityMinimum Sensitivity and SensitivityAccuracyUsage and RuggednessElectrical Parameters

Combating NoiseTo increase the strength of low level signals

before transmission through the wires.

Done with the help of an Instrumentation Amplifier.

Instrumentation AmplifierFinite gainHigh impedance differential inputHigh Common-mode voltage rangeHigh Common-mode rejection (90 dB)

Noise EffectThe connections to the transducer should be

differential to prevent the introduction the noise.

Use of Isolation Amplifiers where the noise environment is so severe that conventional amplifiers can’t survive the signal levels encountered.

Sources of ErrorThese errors occur when transmitting a low-

level signal to any significant distance.A method of reducing errors due to

intervening resistances and the effect of power supply currents is to use current rather than voltages for transmission.

Voltage-to-Frequency ConverterAn Integrator that feeds a comparator, which

in turn drives a one-shot multivibrator. An electronic switch discharges the integrator via a current source.

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

IEEE StandardsIEEE 1451 is a set of smart

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