What is transducer?Where are they used and what for?

1. Name ID
Md.Uzzal Mia 16102923
Md.Kamruzzaman Sumon 16102916
Anisuzzaman Anis 16102915
Welcome to our presentation

2.  What is transducer?Where are they used and what
for?
The device which converts the one form of energy into another is
known as the transducer .The energy transmission may be
electrical,mechanical,che mical ,optical .
Application of transducer
1.It is used for detecting the movement of muscles which is called
acceleromyograph.
2.The transducer measures the load on the engines.
3.It is used as a sensor for knowing the engine knock.
4.It converts the temperature of the devices into an electrical signal
or mechanical work.
5.The transducer is used in the speaker for converting the electrical
signal into acoustic sound.
6.It is used in the antenna for converting the electromagnetic
waves into an electrical signal.

3. Explain what is meant by active transducer and passive
transducer with an example.
• Active transducer
The transducer whose output is obtained in the form of
voltage or current without any additional auxiliary
source is known as the active transducer. Example
Thermocouple,photovoltaic cell.
• Passive transducer
In passive transducer, the output is obtained by
changing the physical properties (resistance,
inductance, and capacitance) of the material. In other
words, the passive transducer takes power from the
external energy source for transduction.Example
thermistor,differential transformer.

4. What is inverse transducer?
 Inverse transducer is defined as a device which converts an
electrical quantity into a non electrical quantity: A piezoelectric
crystal acts as inverse transducer because when a voltage is applied
across its surfaces, it changes its dimensions causing a mechanical
displacement.
Briefly discuss about different types of temperature
transducer?
Definition: The temperature transducer converts the thermal energy
into a physical quantity likes the displacement, pressure and electrical
signal etc.

5. • Contact Temperature Sensor Device
In such type of transducers, the sensing element is directly
connecting to the thermal source. And the heat is
transferred by the phenomenon of conduction.
• Non-contact Type Temperature Sensor Device
The sensing element is directly not contacting the thermal
source. They use convection phenomenon for the transfer
of heat.

6. True RMS responding voltmeter
• True RMS Voltmeter – Complex waveform are most accurately
measured with an rms voltmeter. This instrument produces a
meter indication by sensing waveform heating power, which is
proportional to the square of the rms value of the voltage.
This heating power can be measured by amplifying and
feeding it to a thermocouple, whose output voltages is then
proportional to the Erms.
• However, thermocouples are non-linear devices. This difficulty
can be overcome in some instruments by placing two
thermocouples in the same thermal environment.
• Figure 4.25 shows a block diagram of a true rms responding
voltmeter.

7. •

8. • The effect of non-linear behaviour of the thermocouple in the
input circuit (measuring thermocouple) is cancelled by similar
non-linear effects of the thermocouple in the feedback circuit
(balancing thermocouple). The two couples form part of a
bridge in the input circuit of a dc amplifier.
• The unknown ac voltage is amplified and applied to the
heating element of the measuring thermocouple. The
application of heat produces an output voltage that upsets
the balance of the bridge.

9. • The dc amplifier amplifies the unbalanced voltage; this
voltage is fed back to the heating element of the balancing
thermocouple, which heats the thermocouple, so that the
bridge is balanced again, i.e. the outputs of both the
thermocouples are the same. At this instant, the ac current
in the input thermocouple is equal to the dc current in the
heating element of the feedback thermocouple. This dc
current is therefore directly proportional to the effective or
rms value of the input voltage, and is indicated by the
meter in the output circuit of the dc amplifier. If the peak
amplitude of the ac signal does not exceed the dynamic
range of the ac amplifier, the true rms value of the ac signal
can be measured independently.

10. Avarage responding voltmeter
• A simplified version of a circuit used in a
typical average responding voltmeter is given
in Fig. 4.23.

12. • The applied waveform is amplified in a high gain stabilised
amplifier to a reasonably high level and then rectified and fed
to a dc mA meter calibrated in terms of rms input voltage. In
this meter instrument, the rectified current is averaged by a
filter to produce a steady deflection of the meter pointer. A dc
component in the applied voltage is excluded from the
measurement by an input blocking capacitor preceding the
high gain amplifier.

13. • The ac amplifier has a large amount of negative feedback,
which ensures gain stability for measurement accuracy, and
an increased frequency range of the instrument. The inclusion
of the meter in the feedback path minimises the effect of
diode non-linearity and meter impedance variations on the
circuit performance.

14. • Capacitors in the meter circuit tend to act as storage or
filter capacitors for the rectifier diodes as well as coupling
capacitors for the feedback signal. The diodes acts as
switches to maintain unidirectional meter current despite
changes in the instantaneous polarity of the input voltage.
• Errors in the reading of an average responding voltmeter
may be due to the application of complex waveforms, i.e. a
distorted or nonsinusoidal input or the presence of hum or
noise.
• The accuracy with which an average responding voltmeter
indicates the rms value of a wave with harmonic content
depends not only on the amplitude of the harmonic but
also on the phase.

15. • Q Meter:
• The overall efficiency of coils and capacitors intended
for RF applications is best evaluated using the Q value.
The Q Meter is an instrument designed to measure
some electrical properties of coils and capacitors. The
principle of the Q meter is based on series resonance;
the voltage drop across the coil or capaci¬tor is Q times
the applied voltage (where Q is the ratio of reactance
to resist¬ance, XL/R). If a fixed voltage is applied to the
circuit, a voltmeter across the capacitor can be
calibrated to read. Q directly.

16. At resonance XL= XC and EL= IXL, EC = IXC, E = I R

17. • From the above equation, if E is kept constant the voltage
across the capacitor can be measured by a voltmeter
calibrated to read directly in terms of Q.
• A practical Q meter circuit is shown in Fig. 10.7.

18. • The wide range oscillator, with frequency range
from 50 kHz to 50 MHz, delivers current to a
resistance Rsh having a value of 0.02 Ω. This
shunt resistance introduces almost no resistance
into the tank circuit and therefore represents a
voltage source of a magnitude e with a small
internal resistance. The voltage across the shunt
is measured with a thermocouple meter. The
voltage across the capacitor is measured by an
electronic voltmeter corresponding to Ec and
calibrated directly to read Q.

19. • The oscillator energy is coupled to the tank
circuit. The circuit is tuned to resonance by
varying C until the electronic voltmeter reads
the maximum value. The resonance output
voltage E, corresponding to Ec, is E = Q X
e, that is, Q = E/e. Since e is known, the
electronic voltmeter can be calibrated to read
Q directly.

20. • The inductance of the coil can be determined by
connecting it to the test terminals of the instrument.
The circuit is tuned to resonance by varying either the
capacitance or the oscillator frequency. If the
capacitance is varied, the oscillator frequency is
adjusted to a given frequency and resonance is
obtained. If the capacitance is pre- setted to a desired
value, the oscillator frequency is varied until resonance
occurs. The Q reading on the output meter must be
multiplied by the index setting or the “Multiply Q by”
switch to obtain the actual Q value. The inductance of
the coil can be calculated from known values of the coil
frequency and resonating capacitor (C).

21. • The Q indicated is not the actual Q, because
the losses of the resonating capacitor,
voltmeter and inserted resistance are all
included in the measuring circuit. The actual Q
of the measured coil is somewhat greater than
the indicated Q. This difference is negligible
except where the resistance of the coil is
relatively small compared to the inserted
resistance Rsh.