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1. The metallic parts of the CAPACITIVE TRANSDUCERS must be insulated from each other.
2. Non-linear BEHAVIOUR.
3. This leads loading effects.
4. The cable may be source of loading resulting LOSS of sensitivity.

In this case OUTPUT deviates from the correct value by a CONSTANT factor over the ENTIRE RANGE of transducer.

In this case output deviates from the correct value by a constant factor over the entire range of transducer.

Digital encoding TRANSDUCER or digitiser, ENABLE a LINEAR or rotary DISPLACEMENT to be directly converted into digital form without intermediate form of analog to digital (A/D) conversion.

Digital encoding transducer or digitiser, enable a linear or rotary displacement to be directly converted into digital form without intermediate form of analog to digital (A/D) conversion.

A piezoelectric MATERIAL is one in which an electric potential APPEARS across certain surfaces of a CRYSTAL if the DIMENSIONS of the crystal are changed by the application of the mechanical force.

A piezoelectric material is one in which an electric potential appears across certain surfaces of a crystal if the dimensions of the crystal are changed by the application of the mechanical force.

Digital transducer give digital outputs. Analog transducers outputs are continuous FUNCTIONS of time. If these analog transducers are to be INTERFACED with digital DEVICES, then ONE has to use analog to digital converters.

Digital transducer give digital outputs. Analog transducers outputs are continuous functions of time. If these analog transducers are to be interfaced with digital devices, then one has to use analog to digital converters.

FIBRE optic cable CONSISTS of OUTER core and inner cladding.Data is transmitted in the form of light.It is used for measuring displacement,TORSION.

Fibre optic cable consists of outer core and inner cladding.Data is transmitted in the form of light.It is used for measuring displacement,torsion.

The permeability can INCREASE or decrease depending upon the material, TYPE of STRESS , and the magnetic flux density in the SAMPLE.

The permeability can increase or decrease depending upon the material, type of stress , and the magnetic flux density in the sample.

IRON , NICKEL, 68 PERMALLOY, ferroxcube ECT.

Iron , nickel, 68 permalloy, ferroxcube ect.

Primary quartz, Rochelle SALT, ammonium dihydrogen PHOSPHATE (ADP), and ceramics with barium titanate, dipotassium tartrate, POTASSIUM dihydrogen phosphate and lithium SULFATE.

Primary quartz, Rochelle salt, ammonium dihydrogen phosphate (ADP), and ceramics with barium titanate, dipotassium tartrate, potassium dihydrogen phosphate and lithium sulfate.

They convert PRESSURE or FORCE into electrical charge. These TRANSDUCERS are based UPON the natural phenomenon of certain non-metal and di-electric components.

They convert pressure or force into electrical charge. These transducers are based upon the natural phenomenon of certain non-metal and di-electric components.

These transducer CONVERT input QUANTITY into an electrical OUTPUT which is in the form of PULSES.

These transducer convert input quantity into an electrical output which is in the form of pulses.

it Can be used for measurement of linear and ANGULAR DISPLACEMENT. Can be used for measurement of force and pressure. It can be used as pressure TRANSDUCER. Measurement of humidity in GASES. Commonly used for measurement of level, density, weight.

it Can be used for measurement of linear and angular displacement. Can be used for measurement of force and pressure. It can be used as pressure transducer. Measurement of humidity in gases. Commonly used for measurement of level, density, weight.

• They REQUIRE only small force to operate.
• Have a GOOD FREQUENCY response.
• EXTREMELY sensitive.
• High input impedance

Many INDUSTRIAL variables LIKE displacement, pressure, level, moisture, thickness ETC can be transduced into an electrical VARIATION using capacitance variation as the primary sensing principle.

Many industrial variables like displacement, pressure, level, moisture, thickness etc can be transduced into an electrical variation using capacitance variation as the primary sensing principle.

Another common VERSION of the VARIABLE reluctance principle. This is an ACCELEROMETER for measurement of accelerometer for measurement of ACCELERATION in the range ± 4g. Since the force required to accelerate a mass is PROPORTIONAL to the acceleration.

Another common version of the variable reluctance principle. This is an accelerometer for measurement of accelerometer for measurement of acceleration in the range ± 4g. Since the force required to accelerate a mass is proportional to the acceleration.

The primary is excited with alternating CURRENT. This induces a VOLTAGE in to the secondary. The AMPLITUDE of this output voltage varies with the mutual INDUCTANCE between the TWO coils and this varies with the angle of rotation.

The primary is excited with alternating current. This induces a voltage in to the secondary. The amplitude of this output voltage varies with the mutual inductance between the two coils and this varies with the angle of rotation.

Ideally the output VOLTAGE at the null position should be EQUAL to zero. HOWEVER, in ACTUAL practice there exists a small voltage at the null position.

Ideally the output voltage at the null position should be equal to zero. However, in actual practice there exists a small voltage at the null position.

• Change of self inductance
• Change of MUTUAL inductance
• PRODUCTION of eddy CURRENTS.

Transducers BASED on the variation of inductance are another GROUP of importance devices used in MANY application. In these transducers self inductance or the mutual of a couple of COILS is changed when the quantity to be measured is varied.

Transducers based on the variation of inductance are another group of importance devices used in many application. In these transducers self inductance or the mutual of a couple of coils is changed when the quantity to be measured is varied.

• Filament CONSTRUCTION
• Material of the filament wire
• BASE carrier material or backing material
• CEMENT USED to BOND the filament to the carrier
• Lead wire connections.

1. Unbonded METAL strain gauges
2. BONDED metal wire strain gauges
3. Bonded metal foil strain gauges
4. VACUUM deposited THIN metal film strain gauges
5. Sputter deposited thin metal strain gauges
6. Bonded semiconductor strain gauges
7. Diffused metal strain gauges.

ADVANTAGES : 

• Inexpensive
• Useful for MEASUREMENT of large amplitudes
• Efficiency is very high
• FREQUENCY response of wire wound potentiometers is LIMITED

DISADVANTAGES :

Require a large force to move

Advantages : 

Disadvantages :

Require a large force to move

Basically a RESISTANCE potentiometer, or SIMPLY a POT, (a RESISTIVE potentiometer used for the purposes of voltage division is called a POT) consists of a resistive element provided with a sliding contact. The POT is a passive TRANSDUCER.

Basically a resistance potentiometer, or simply a POT, (a resistive potentiometer used for the purposes of voltage division is called a POT) consists of a resistive element provided with a sliding contact. The POT is a passive transducer.

It is DEFINED as time required for the system to rise from 0 to 100 percent of its final VALUE.

It is defined as time required for the system to rise from 0 to 100 percent of its final value.

The range of the transducer is specified as from the lower VALUE of input to higher value of input.

The SPAN of the transducer is specified as the DIFFERENCE between the higher and lower LIMITS of RECOMMENDED input values.

The range of the transducer is specified as from the lower value of input to higher value of input.

The span of the transducer is specified as the difference between the higher and lower limits of recommended input values.

When the input to a TRANSDUCER is increased from zero, there is a MINIMUM VALUE below which no output can be DETECTED .This minimum value of the input is defined as the threshold of the transducer.

When the input to a transducer is increased from zero, there is a minimum value below which no output can be detected .This minimum value of the input is defined as the threshold of the transducer.

Accuracy is the closeness to true value WHEREAS precision is the closeness AMONGST the READINGS .

precision is the degree of closeness with which a given value may be REPEATEDLY measured.

Accuracy is the closeness to true value whereas precision is the closeness amongst the readings .

precision is the degree of closeness with which a given value may be repeatedly measured.

The damping ratioV is an important parameter which decides the nature of OSCILLATION in the transducer output . when V =0 , the second – order system is SAID to be un DAMPED and the system behaves like an oscillator . when V =1 , the second – order system is said to be critical damped and when V >1 , the second – order system is said to be over damped.

The damping ratioV is an important parameter which decides the nature of oscillation in the transducer output . when V =0 , the second – order system is said to be un damped and the system behaves like an oscillator . when V =1 , the second – order system is said to be critical damped and when V >1 , the second – order system is said to be over damped.

Frequency response is THUS DEFINED as the STEADY – state output of a transducer When it is excited with sinusoidal input . the frequency response is represented with the HELP of TWO plots namely amplitude radio verses frequency and phase angle shift versus frequency.

Frequency response is thus defined as the steady – state output of a transducer When it is excited with sinusoidal input . the frequency response is represented with the help of two plots namely amplitude radio verses frequency and phase angle shift versus frequency.

The input- output relationship of a ZERO- order TRANSDUCER is given by

Y(t) = K r(t)

Where r(t) is the input, Y(t) is the output and K is the static – sensitivity of the transducer.

EXAMPLE for zero- order transducer is a potentiometer.

The input- output relationship of a zero- order transducer is given by

Y(t) = K r(t)

Where r(t) is the input, Y(t) is the output and K is the static – sensitivity of the transducer.

Example for zero- order transducer is a potentiometer.

1. IMPULSE INPUT
2.  Step input
3.  Ramp input
4.  Parabolic input 
5.  SINUSOIDAL input

1. ZERO- ORDER TRANSDUCERS
2.  FIRST - order transducers
3. Second-order transducers
4.  Higher-order transducers

Many measurements are concerned with RAPIDLY VARYING quantities and , therefore, for such cases we must examine the dynamic RELATIONS which EXIST between the output and the input . This is NORMALLY done with the help of differential equations . Performance criteria based upon dynamic relations constitute the Dynamic Characteristics.

Many measurements are concerned with rapidly varying quantities and , therefore, for such cases we must examine the dynamic relations which exist between the output and the input . This is normally done with the help of differential equations . Performance criteria based upon dynamic relations constitute the Dynamic Characteristics.

STATIC characteristics of a measurement system are, in GENERAL, those that must be considered when the system or instrument is used to measure a condition not varying with TIME.

static characteristics of a measurement system are, in general, those that must be considered when the system or instrument is used to measure a condition not varying with time.

1.Operating principle
2.Sensitivity
3.Operating range.
4.Accuracy.

1.Operating principle
2.Sensitivity
3.Operating range.
4.Accuracy.

A device which converts an electrical quantity into an non-electrical quantity.A piezo-electric crystal ACTS as a inverse transducer because WHWN a voltage is APPLIED ACROSS its SURFACES ,it changes its dimensions causing a mechanical displacement.

A device which converts an electrical quantity into an non-electrical quantity.A piezo-electric crystal acts as a inverse transducer because whwn a voltage is applied across its surfaces ,it changes its dimensions causing a mechanical displacement.

When a FORCE is APPLIED to piezo-electric crystals ,they produce an OUTPUT VOLTAGE.

When a force is applied to piezo-electric crystals ,they produce an output voltage.

The HAPPENINGS or disturbances about which we are unaware and lumped TOGETHER are called random errors or residual errors.Since these errors REMAIN EVEN after the systematic errors are taken CARE of,they are called residual errors.

The happenings or disturbances about which we are unaware and lumped together are called random errors or residual errors.Since these errors remain even after the systematic errors are taken care of,they are called residual errors.

The ability to trace the accuracy of the STANDARD BACK to its ultimate source in fundamental standards of NATIONAL INSTITUTE of Science and TECHNOLOGY is termed “Traceability”.

The ability to trace the accuracy of the standard back to its ultimate source in fundamental standards of National Institute of Science and Technology is termed “Traceability”.

It refers to a process in which all the inputs(DESIRED,modifying,interfering) EXCEPT ONE are kept at some constant values.

It refers to a process in which all the inputs(desired,modifying,interfering) except one are kept at some constant values.

Fundamental units in mechanics are measures of length,mass and time and those are fundamental to most other physical quantities and hence they are called PRIMARY fundamental units Measures of certain physical quantities in thermal ,ELECTRICAL and illumination fields are also REPRESENTED by fundamental units and are USED only where those DISCIPLINES are involved and hence called auxiliary fundamental units.

Fundamental units in mechanics are measures of length,mass and time and those are fundamental to most other physical quantities and hence they are called Primary fundamental units Measures of certain physical quantities in thermal ,electrical and illumination fields are also represented by fundamental units and are used only where those disciplines are involved and hence called auxiliary fundamental units.

1.Absolute UNITS
2.Fundamental and DERIVED units
3.Electromagnetic units
4.Electrostatic units

1.Absolute units
2.Fundamental and derived units
3.Electromagnetic units
4.Electrostatic units

These transducers convert the input quantity into an analog output which is a continuous function of TIME. THUS a strain gauge, an LVDT, a thermocouple or a THERMISTORS may be CALLED analog transducer, as they give an output which is a continuous function of time.

These transducers convert the input quantity into an analog output which is a continuous function of time. Thus a strain gauge, an LVDT, a thermocouple or a thermistors may be called analog transducer, as they give an output which is a continuous function of time.

In the ABSENCE of external power, TRANSDUCER can WORK and it is called ACTIVE transducer. Example VELOCITY, temperature, light can be transdued with the help of active transducer.

In the absence of external power, transducer can work and it is called active transducer. Example velocity, temperature, light can be transdued with the help of active transducer.

In the ABSENCE of external power, TRANSDUCER cannot WORK and it is called a PASSIVE transducer. Example capacitive , inductive, resistance transducers.

In the absence of external power, transducer cannot work and it is called a passive transducer. Example capacitive , inductive, resistance transducers.

The OUTPUT of the BOURDON tube is given to the INPUT of the LVDT. There are two STAGES of transduction, firstly the pressure is converted into a displacement by the Bourdon tube then the displacement is converted into analog VOLTAGE by LVDT. Here LVDT is called secondary transducer. Electrical device can act as a secondary transducer.

The output of the Bourdon tube is given to the input of the LVDT. There are two stages of transduction, firstly the pressure is converted into a displacement by the Bourdon tube then the displacement is converted into analog voltage by LVDT. Here LVDT is called secondary transducer. Electrical device can act as a secondary transducer.

Bourdon tube ACTING as a primary transducer, SENSES the pressure and convert the pressure into displacement. No OUTPUT is given to the input of the bourdon tube. So it is called primary transducer. Mechanical device can ACT as a primary transducer.

Bourdon tube acting as a primary transducer, senses the pressure and convert the pressure into displacement. No output is given to the input of the bourdon tube. So it is called primary transducer. Mechanical device can act as a primary transducer.

Transducer is a DEVICE which CONVERT one form of energy into electrical energy. A THERMOCOUPLE CONVERTS heat energy into electrical voltage.

Transducer is a device which convert one form of energy into electrical energy. A thermocouple converts heat energy into electrical voltage.

The SPECIFICATION of limiting error is in itself UNCERTAIN because the MANUFACTURE himself is not SURE about the ACCURACY because of the presence of random errors.

The specification of limiting error is in itself uncertain because the manufacture himself is not sure about the accuracy because of the presence of random errors.

• DIRECT COMPARISON METHOD
• INDIRECT comparison method