Chapter 10: Phase and Time
measurement
Content
lGeneral Concept
lMeasuring phase by straight conversion method
lMeasuring phase by complement conversion method
General Concept
lPhase angle
–Basic parameters of oscillation process
X(t) = Xm.cos(ωt+φ)
–2 oscillations with the same frequency
x1 = X1m.cos(ωt+φ1)
x2 = X2m.cos(ωt+φ2)
Dephasing angle: φ = φ1 – φ2
If frequency of 2 oscillation are multiple
hoăc
With multi-harmonic signal, dephasing angle φ is angle of first
harmonic.
2
2
1
1
ϕ
ω
ω
ϕϕ
−=
1
1
2
2
ϕ
ω
ω
ϕϕ
+−=
General Concept
lPhase angle measurement method:
–Based on conversion method : straight conversion method and
complement conversion method
–Based on measured information achieving method : use
information when signal overcomes a determined threshold,
and all achieved information is used.
Measuring phase angle by straight conversion method
lElectrodynamic Fazometter
–Use electrodynamic logometer indicator
–Phase angle between U and I is measured phase φ
–U va I lêch nhau goc φ cân đo
–Moving coil 1 is connected in series with its current I1
–Movig coil 2 is connected with L2, current I2
Choose I1=I2
β = γ
 α = φ
1 1 1 1
2 2 2 2
cos( . ) cos( ) cos( )
( ) cos( . ) cos cos
I I I I I
f F F F
I I I I I
b j g a
aj a
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= = =
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