Phase
What is Phase?
Phase is the time difference between two sig-
nals of the same frequency, expressed as an
angle.
The traditional method to measure phase de
-
lay with a timer/counter is a two-step process
consisting of two consecutive measurements,
first a period measurement and immediately
after that a time interval measurement. The
phase delay is then mathematically calculated
as:
360°´ -()Time Interval A B
Period
or in other words:
Phase A B Time Delay FREQ-= °´ ´360
A somewhat more elaborate method is used in
these counters. It allows the necessary mea
-
surements to be performed in one pass by us
-
ing time-stamping. Two consecutive
time-stamps from trigger events on channel A
and two corresponding time-stamps from
channel B are enough to calculate the result,
including sign.
Resolution
The frequency range for phase is up to
160 MHz and the resolution depends on the
frequency. For frequencies below 100 kHz the
resolution is 0.001° and for frequencies above
10 MHz it is 1°. It can be further improved by
averaging through the built-in statistics func
-
tions.
What is Phase? 4-17
Measuring Functions
B
A
Phase?
Fig. 4-18 Phase delay.
P e r i o d ( T )
T i m e d e l a y (
D
t )
f
=
D
t
*
3 6 0
o
T
A
B
Fig. 4-19 Traditional phase definition.
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