Download - Discussion of the experiment
Discussion of the experiment
Weifeng Su04/10/2009
Wheatstone bridgePrinciple: RA & RB are connected in series.
RX & RS are connected in series.
RA & RX are connected in parallel.
RB & RS are connected in parallel.
When bridge is balanced,
1) IG=0, I1=I3 and I2=I4
2) potential of point ‘2’ = potential of
point ‘4’,
U2=U4So, I1RA=I2Rx (1)
I3RB=I4Rs (2)
(1)/(2),
Fig. 1The circuit diagram of a Wheatsone bridge
I1
I2
IG
I3
I4
SB
AX
S
B
X
A RR
RR
R
R
R
R
Wheatstone bridge
Set up the circuit
)()()( 22
21 ABABA RuRuRu
G
S2
E S1
• Balancing the bridge
coarse adjustment & finer adjustment
How can we get the largest sensitivity?
Determine the measurement uncertainty of RX
when the sensitivity M is the largest.2222 )
)(()
)(()
)(()
)((
S
S
B
BA
x
X
B
SAX R
Ru
R
Ru
R
Ru
R
Ru
R
RRR
A
10/)(;0)()( 111 SSBBBAB RRuRuRu
3)(2
aRu AB
Oscilloscope
Principle:
Oscilloscope Principle:
http://chem.ch.huji.ac.il/instruments/test/oscilloscope_principle_animated.html
Oscilloscope
Lissajous figure Lissajous Figures are a special case of parametric equations, where x a
nd y are in the following form: x = A sin(at + δ)
y = B sin(bt + γ) Lissajous curves can be seen on oscilloscopes and are the result of combi
ning 2 trigonometric curves at right angles.
http://pagesperso-orange.fr/olivier.granier/meca/simul/lisajou/simul.html
Oscilloscope How to measure a signal by oscilloscope?
To measure aDC signal
0.5V/DIV
2.68DIV×0.5V/DIV=1.34V
Oscilloscope How to measure a signal by oscilloscope?
To measure anAC signal
0.5V/DIV2ms/DIV
Peak-peak amplitude:3.56DIV×0.5V/DIV=1.78V
Period: T=3.16DIV×2ms/DIV=6.32ms;Frequency:f=1/T=158Hz
The property of diodeto allow an electric current in one direction
half wave rectification full-wave rectification
Input signal
Output signal
Input signal
Output signal