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.
1
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 25C. What is the
resistance when the temperature rises up to 55C? (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 0C 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 400C.
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 )
3
0
