AB57
OWEN’S BRIDGE
Analog Lab
Experiment Board
Ver. 1.0
QUALITY POLICY
To be a Global Provider of Innovative and Affordable
Electronic Equipments for Technology Training by
enhancing Customer Satisfaction based on
Research, Modern manufacturing techniques and
continuous improvement in Quality of the products
and Services with active participation of employees.
An ISO 9001: 2000 company
94-101, Electronic Complex, Pardesipura INDORE-452010, India.
Tel.: 91-731-2570301 Fax: 91-731-2555643
Email: info@scientech.bz Web: www.scientech.bz
AB57
Scientech Technologies Pvt. Ltd.
2
AB57
OWEN’S BRIDGE
AB57
TABLE OF CONTENTS
1.
Introduction
4
2.
Theory
6
3.
Owen’s Bridge
9
4.
Experiment
11
To measure the value of unknown inductance with the help of
Owen’s bridge.
5.
Observation table
13
6.
Datasheet
14
7.
Warranty
16
8.
List of Service Centers
17
9.
List of Accessories with AB57
18
10.
Notes
19
Scientech Technologies Pvt. Ltd.
3
AB57
INTRODUCTION
AB57 is a compact, ready to use OWEN’S BRIDGE experiment board.
This bridge is the simplest way to measure the induction
of an inductor in terms of capacitor; by comparing the
branch impedance of the bridge. It can be used as stand
alone unit with external DC power supply and function
generator ST4064 or can be used with SCIENTECH
ANALOG LAB ST2612, which has built in DC power
supply, AC power supply, function generator, modulation
generator, continuity tester, toggle switch, and
potentiometer.
List of boards :
Model
Name
AB01
AB02
AB03
AB04
AB05
AB06
AB07
AB08
AB09
AB10
AB11
AB12
AB13
AB14
AB15
AB16
AB17
AB18
AB19
AB20
AB21
AB22
AB23
AB25
Diode characteristics (Si, Zener, LED)
Transistor characteristics (CB NPN)
Transistor characteristics (CB PNP)
Transistor characteristics (CE NPN)
Transistor characteristics (CE PNP)
Transistor characteristics (CC NPN)
Transistor characteristics (CC PNP)
FET characteristics
Rectifier Circuits
Wheatstone Bridge
Maxwell’s Bridge
De Sauty’s Bridge
Schering Bridge
Darlington Pair
Common Emitter Amplifier
Common Collector Amplifier
Common Base Amplifier
Cascade Amplifier
RC-Coupled Amplifier
Direct Coupled Amplifier
Class A Amplifier
Class B Amplifier (push pull emitter follower)
Class C Tuned Amplifier
Phase Locked Loop (FM Demodulator & Frequency
Divider / Multiplier)
Multivibrator ( Mono stable / Astable)
AB28
Scientech Technologies Pvt. Ltd.
4
AB57
AB29
AB30
AB31
AB32
AB33
AB39
AB41
AB42
AB43
AB44
AB45
AB51
AB52
AB53
AB54
AB56
AB64
AB65
AB66
AB67
AB68
AB80
AB81
AB82
AB83
AB84
AB85
AB88
AB89
AB90
AB91
AB92
AB93
AB96
AB97
AB101
AB102
AB106
F-V and V-F Converter
V-I and I-V Converter
Zener Voltage Regulator
Transistor Series Voltage Regulator
Transistor Shunt Voltage Regulator
Instrumentation Amplifier
Differential Amplifier (Transistorized)
Operational Amplifier (Inverting / Non-inverting /
Differentiator)
Operational Amplifier (Adder/Scalar)
Operational Amplifier (Integrator/ Differentiator)
Schmitt Trigger and Comparator
Active filters (Low Pass and High Pass)
Active Band Pass Filter
Notch Filter
Tschebyscheff Filter
Fiber Optic Analog Link
RC – Coupled Amplifier with Feedback
Phase Shift Oscillator
Wien Bridge Oscillators
Colpitt Oscillator
Hartley Oscillator
RLC Series and RLC Parallel Resonance
Kirchoff’s Laws (Kirchoff’s Current Law & Kirchoff’s
Voltage Law)
Thevenin’s and Maximum power Transfer Theorem
Reciprocity and Superposition Theorem
Tellegen’s Theorem
Norton’s theorem
Diode Clipper
Diode Clampers
Two port network parameter
Optical Transducer (Photovoltaic cell)
Optical Transducer (Photoconductive cell/LDR)
Optical Transducer (Phototransistor)
Temperature Transducer (RTD & IC335)
Temperature Transducer (Thermocouple)
DSB Modulator and Demodulator
SSB Modulator and Demodulator
FM Modulator and Demodulator
Scientech Technologies Pvt. Ltd.
5
AB57
………… and many more
Scientech Technologies Pvt. Ltd.
6
AB57
THEORY
Bridge circuits are extensively used for measuring component value such as
R, C and L. It has four arms consisting of resistor or inductor or capacitor
that form a closed circuit. A DC or AC source applied to two opposite
junction and a null detector connected to the other two junctions. The
bridge circuits work as a pair of two-component voltage dividers connected
across same source voltage, with a null detector connected between them to
indicate a condition of ‘balance’ at zero volts. Bridges can be classified in
two types: DC bridges and AC bridges. DC bridges are used in
measurement of unknown resistance and it is excited by DC source and
galvanometers are used for null detection.
AC bridges or Alternating Current bridges are consists of four arms, an AC
source of excitation and a balance detector. In an AC bridge each arm has
impedance and the detector is sensitive towards the slightest change in arm
impedance. The usefulness of AC bridge is not restricted to the
measurement of unknown impedance and associate parameter like
inductance, capacitance, storage factor, loss, and dissipation factor.
These circuits find other application in communication system and complex
electronics circuits such as phase shifting, providing feed back path for
oscillator and amplifiers, and filtering out undesirable signals. For
measurement at low frequencies power line may act as the source of the
supply to bridge circuits and for higher frequencies electronics oscillators
are used as bridge source supplies. Oscillators have advantage that
frequency is constant easily adjustable and determinable with accuracy the
waveform is much closed to a sine wave and there power output is
sufficient for most bridge measurement.
Detectors most commonly used for A.C. bridges are
1.
Head phones
2.
Vibration galvanometers
3.
Tunable amplifiers detectors
Headphones are widely used as detectors at frequencies of 250 Hz and up
to 3 or 4 kHz. They are most sensitive detectors for this range when
working at a single frequency a tuned detector normally gives the greatest
sensitivity and discrimination against harmonics in the supply. Vibration
galvanometers are extremely useful for power and low audio frequency
ranges. Vibration galvanometers are manufactures to work at various
Scientech Technologies Pvt. Ltd.
7
AB57
frequencies ranging from 5 Hz to 1000 Hz but are most commonly used
below 200 Hz, as below this frequency they are more sensitive that the
head phones. Tunable amplifiers detectors are the most versatile of the
detectors the transistors amplifiers can be tuned electrically and thus can be
made to respond to a narrow bandwidth at the bridge frequency .The output
of the amplifier is fed to a pointer type instrument this detector can be used,
over a frequency range of 10 Hz to 100 kHz.
General equation for bridge balance:
Basic AC bridge circuit is shown below the four arm of the bridge is
impedance Z1, Z2, Z3, Z4.The condition for balance of bridge requiring that
there should be no current through the detector. This requires that the
potential difference between points ‘b’ and ‘d’ should be zero. This will be
the case when the voltage drop from ‘a’ to ‘b’ equals the voltage drop from
‘a’ to ‘d’, both in magnitude and phase. In complex notation we can, thus,
write:
E1 = E2
I1Z1 = I2Z2
Also at balance,
I1= I3 = E/Z1+Z2
I2= I4= E/Z2+Z4
Substituting the Eq.
We Get
Z1Z4 = Z2Z3
Eq. states that the product of impedances of one pair opposite arms must
equal the product of impedance of the other pair of opposite arms in
complex notation. This means that both magnitude and phase angle of the
impedance must be taken into account.
Two conditions must be satisfied simultaneously when balancing the A.C.
bridge
The first condition is that the magnitude of impedances satisfies the
relationship:
Z1 Z4 = Z2Z3
Z1 =
Z2
Scientech Technologies Pvt. Ltd.
Z3
Z4
8
AB57
The impedance of the arm is vector complex quantities that posses phase
angles. It is thus necessary to adjust both the magnitude and phase angles to
achieve balance, i.e. the bridge must be balance for both the reactance and
the resistive component.
The second condition is that the phase angles of impedance satisfy the
relationship:
θ1+θ4=θ2+θ3
The phase angles are positive for inductive impedance and negative for
capacitance impedance.
Scientech Technologies Pvt. Ltd.
9
AB57
OWEN’S BRIDGE
In Owen’s bridge, the inductance of an inductor is measures in terms of a
capacitor. Figure 1 shows the basic Owen’s bridge circuit configuration.
Owen’s bridge is consisting of four arms. Its first arm has unknown
inductance. Third arm is consisting of pure resistive element and fourth arm
has standard capacitor. Variable resistance in second arm, which also have a
variable capacitor to balance ‘Q’ factor of the bridge, achieves bridge’s
balance condition.
Lx = inductor with unknown inductance,
Rx = internal resistance of inductor,
R2 = variable resistance,
R3= non-inductive resistance,
R4= non-inductive resistance,
C4 = standard capacitor,
C2 = variable capacitor.
At balance,
(Rx+ jωLx).(1/ jωC4) = (R2+ 1/jωC2). R3
Separating the real and imaginary terms,
Lx = R2.R3.C4
……………. (1)
and
ωLx/Rx
= ωC2R2
……………. (2)
Whilst, ωC2R2 represent the ‘Q’ factor of capacitor C2 and ωLx/Rx
represents the ‘Q’ factor of unknown inductance Lx, thus it is absolutely
necessary to know the exact value of frequency to determine the balance
condition. Hence it’s necessary to satisfy the ‘Q’ factor of bridge to remove
any frequency term in balance condition or to achieve balance without any
frequency component.
Thus,
Putting the value of Lx in Eq.2
Rx = R3.C4/C2
……………. (3)
The ‘Q’ factor of inductor varies due to variation in inductance and hence
the variable capacitor is used in the bridge.
Scientech Technologies Pvt. Ltd.
10
AB57
Advantages :
1.
Owen’s bridge can be used to measure over a wide range of
inductance.
2.
Convergence of balance condition is much easier than other bridges
due to R2 and C2; two variables are in same arm.
3.
The balance equations are quit easy and do not contain any frequency
terms.
Disadvantages :
1.
The Owen’s bridge requires a variable capacitor that is expensive
and makes its accuracy rather low.
2.
The value of C2 tends to become rather large when measuring high Q
coils.
Owen’s Bridge
Fig. 1
Scientech Technologies Pvt. Ltd.
11
AB57
EXPERIMENT
Object :
To measure the value of unknown inductance with the help of Owen’s
bridge.
Apparatus required :
1.
Analog Board, AB57
2.
DC power supplies +/–12V from external source or ST2612 Analog
lab
3.
Function generator ST4064
4.
2 mm patch cords
5.
Digital multimeter
Circuit diagram :
Circuit used to measure the value of unknown inductance is shown in
Figure 2.
Scientech Technologies Pvt. Ltd.
12
AB57
Fig. 2
Scientech Technologies Pvt. Ltd.
13
AB57
Procedure :
•
Connect +/–12V dc power supply and ground at their indicated
position from external source or ST2612 Analog lab.
1. Connect function generator ST4064 probes at Vin terminals.
2. Set the 5Vpp, 1 KHz input sinusoidal signal of function generator.
3. Connect 2mm patch cord between socket ‘a’ and ‘d’ to determine the
inductance of inductor Lx1.
4. Connect 2mm patch cord between capacitor C21 and socket ‘e’ to
satisfy the ‘Q’ factor of the bridge.
5.
Switch ON the power supply.
6.
Rotate the potentiometer to find a condition where null or minimum
sound is generated.
7.
Switch off the power supply and function generator.
8. Take the reading of potentiometer resistance R2 at test-point ‘tp4’ and
socket ‘e’.
9. Measure the value of Rx1 between test-point ‘tp1’ and socket ‘a’.
10. Calculate the value of inductance Lx1 and resistance Rx1.
11. Connect 2mm patch cord between socket ‘b’ and ‘d’ to determine the
inductance of inductor Lx2; and between capacitor C22 and socket ‘e’
to satisfy the ‘Q’ factor of the bridge.
12. Repeat the above step from 5 to 8.
13. Measure the value of Rx2 between test-point ‘tp2’ and socket ‘b’ and
calculate the value of Lx2 and Rx2.
14. Connect 2mm patch cord between socket ‘c’ and ‘d’ to determine the
inductance of inductor Lx3; and between capacitor C23 and socket ‘e’
to satisfy the ‘Q’ factor of the bridge.
15. Repeat the above step from 5 to 8.
16. Measure the value of Rx3 between test-point ‘tp3’ and socket ‘c’ and
calculate the value of Lx3 and Rx3.
Scientech Technologies Pvt. Ltd.
14
AB57
OBSERVATION TABLE
S.
No.
Lx =
R2.R3.C4
(µ H)
(calculated)
R2
(Ω)
(measured)
Error
(measured)
Rx =
R3.C4/C2
(Ω)
(calculated)
Rx
(Ω)
(calculated)
Calculation :
Measured value of R2 is. …………. Ω
Calculate the value of Lx by the formula:
Lx = R2.R3.C4
Calculate the values of Rx by the formula:
Rx
= R3.C4/C2
Result :
The inductance Lx …….. = ………,
The resistance Rx ……... = ………,
Note :
The inductance Lx1 = 220 µ H
The inductance Lx2 = 470 µ H
The inductance Lx3= 680 µ H
Scientech Technologies Pvt. Ltd.
15
AB57
Scientech Technologies Pvt. Ltd.
16
AB57
DATASHEETS
Scientech Technologies Pvt. Ltd.
17
AB57
Scientech Technologies Pvt. Ltd.
18
AB57
WARRANTY
1.
We guarantee the instrument against all manufacturing defects
during 24 months from the date of sale by us or through our dealers.
2.
The guarantee covers manufacturing defects in respect of indigenous
components and material limited to the warranty extended to us by
the original manufacturer, and defect will be rectified as far as lies
within our control.
3.
The guarantee will become INVALID.
a)If the instrument is not operated as per instruction given in the
instruction manual.
b)If the agreed payment terms and other conditions of sale are not
followed.
c) If the customer resells the instrument to another party.
d)Provided no attempt have been made to service and modify the
instrument.
4.
The non-working of the instrument is to be communicated to us
immediately giving full details of the complaints and defects noticed
specifically mentioning the type and sr. no. of the instrument, date of
purchase etc.
5.
The repair work will be carried out, provided the instrument is
dispatched securely packed and insured with the railways. To and
fro charges will be to the account of the customer.
DISPATCH PROCEDURE FOR SERVICE
Should it become necessary to send back the instrument to factory please
observe the following procedure:
1)
Before dispatching the instrument please write to us giving full
details of the fault noticed.
2)
After receipt of your letter our repairs dept. will advise you
whether it is necessary to send the instrument back to us for repairs
or the adjustment is possible in your premises.
Dispatch the instrument (only on the receipt of our advice) securely packed
in original packing duly insured and freight paid along with accessories and
a copy of the details noticed to us at our factory address.
Scientech Technologies Pvt. Ltd.
19
AB57
LIST OF SERVICE CENTERS
1. Scientech Technologies Pvt. Ltd.
90, Electronic Complex
Pardesipura,
INDORE – 452010
2. Scientech Technologies Pvt. Ltd.
First Floor, 14, Uday Park,
NEW DELHI – 110049
3. Scientech Technologies Pvt. Ltd.
New no.2, Old no.10, 4th street
Venkateswara nagar, Adyar
CHENNAI – 600025
4. Scientech Technologies Pvt. Ltd.
202/19, 4th main street
Ganganagar,
BANGALORE- 560032
5. Scientech Technologies Pvt. Ltd.
8,1st floor, 123-Hariram Mansion,
Dada Saheb Phalke road,
Dadar (East), MUMBAI –400014
6. Scientech Technologies Pvt. Ltd.
988, Sadashiv Peth,
Gyan Prabodhini Lane,
PUNE – 411030
7. Scientech Technologies Pvt. Ltd
SPS Apartment, 1st Floor
2, Ahmed Mamoji Street,
Behind Jaiswal Hospital,
Liluah, HOWRAH-711204 W.B.
8. Scientech Technologies Pvt. Ltd
Flat No. 205, 2nd Floor,
Lakshminarayana Apartments
‘C’ wing, Street No. 17,
Himaytnagar,
HYDERABAD- 500029
Scientech Technologies Pvt. Ltd.
Ph: (0731) 5202959
Email: info@scientech.bz
Ph.: (011) 26513912, 26864943
Fax: (011) 26864943.
Email: ndel@scientech.bz
Ph.: (044) 42187548, 42187549
Fax: (044) 42187549
Email: chennai@scientech.bz
Ph.: (080) 51285011
Fax: (080) 51285022
Email: bangalore@scientech.bz
Ph.: (022) 56299457
Fax: (022) 24168767
Email: stplmum@vsnl.net
Ph.: (020) 24461673
Fax: (020) 24482403
Email: pune@scientech.bz
Ph.: +913355266800
Email: kolkata@scientech.bz
Ph.: (040) 55465643
Email: hyd@scientech.bz
20
AB57
LIST OF ACCESSORIES
1.
2mm Patch cord (Red) ....................................................................2 Nos.
2.
2mm Patch cord (Black) .................................................................2 Nos.
3.
2mm Patch cord (Blue) ...................................................................3 Nos.
Scientech Technologies Pvt. Ltd.
21
AB57
NOTES
Scientech Technologies Pvt. Ltd.
22
AB57
NOTES
Scientech Technologies Pvt. Ltd.
23