TUTORIAL 4-BENP 2183
FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER
BENP 2183 – ELECTRONICS INSTRUMENTATION
TUTORIAL 4
1. Define what is transducer and briefly explain the parameters of electrical transducer must
have.
2. What is the difference between active and passive transducers?
3. A resistive displacement transducer with a shaft stroke of 5 in. is used in the circuit of
Figure 1.The applied voltage V1 is 10V. What displacements do the following voltages
indicate: 2V, 4V, 6V?(Refer Fig.13.2 (a) in the text book)
A
V1
R1
11
R2
W
Vo
11
B
Figure 1
4. Explain the working principle of a wire bonded strain gauge.
5. A strain gauge having a gauge factor of 5. If the strain gauge is attached to a metal bar
that stretches from 10 to 10.2 in., what is the percentage change in resistance? If the
unstrained value of resistance is 120, what is the value after strain?
6. A strain gauge with a gauge factor of 5 has a resistance of 500. It is to be used in test in
which the strain to be measured may be as low as 5 x 10-6. What will the change in
gauge resistance be?
7. A capacitive type pressure transducer has two metal plates that have an affective plate
area of 4cm2 and 0.5 cm apart. A 200psi pressure on one plate will cause the separation
between the plates to decrease by 0.04 cm. if no pressure is applied to the capacitor; it
has a capacitance of 400pF. Determine the capacitance value if 200psi is applied to the
transducer.
8. Give the difference between a self generating inductance and a passive inductive
transducer. Give an example for each type of inductive transducer.
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TUTORIAL 4-BENP 2183
9. An AC LVDT with a secondary voltage of 5V has a range of ±1.0 in. Find:
a) The core movement from center when the output voltage is -3V.
b) The plot of core position versus output voltage for output voltages varying from +3V
to -4.5V.
10. What is RTD and where is it used?
11. What is the different between a thermocouple and a thermistor?
12. A platinum resistance thermometer has a resistance of 200 at 25C. What is the
resistance when the temperature rises up to 55C? (use  = 0.00392/C)
13. Figure 2 shows the circuit of a bridge configuration Resistance Temperature Detector
(RTD) that is used in temperature measurement. The platinum RTD that is used in the
circuit has a temperature coefficient of 0.36/C and the resistance at the reference
temperature 0C of 500.
RF
R
5V
R
RA
Va
-
RTD
OUT
RA
Vb
+
Vo
R
RF
0
Figure 2
a)
Calculate the resistance of the RTD wire, R (T) at 400C.
b)
If the value of R is 400, RA has the same value of R and RF is ten times R,
calculate the output voltage V0.
R
(Hint: Vo   F
 RA
c)

Va  Vb )

List three advantages of using platinum RTD
14. An inductive transducer Lx is used to measure varied distance
reference transducer. The circuit design is in Figure 3.
2
   with Lref as a
TUTORIAL 4-BENP 2183
+
R2
OUT
Lx
1
R3
-
2
R1
1
Lref
-
2
OUT
OUT
Vin
RA
+
R1
Vo1
0
+
RL
Vo2
0
-
R2
OUT
+
R3
0
0
Figure 3
a) Find the relationship
with the ratio
Vo1
A
2 A
if Lx   0 r N x2
and Lref   0 r N ref
Vin
  

Nx
= 0.85.
N ref
b) If   0.1 and Vin = 2V sin ωt, find Vo1.
(Hint: Do not solve sin ωt )
 R  2 R  R A 
 with R1 = R3 = 2R,
c) Find Vo2 if the amplifier gain, Av   3  1
 R2  R A 
R2 = R and RA =
R
.
2
(Hint: Do not solve sin ωt )
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