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P
T
P
1
P
T
P
2
P
T
P
3
Chapter 13: Measurements of the signal by oscilloscope
In the drawing below, the points where to connect the oscilloscope are shown:
Point B shows the quality of
the signal received
In the graphic here below the wave shapes concerning the signal quality are shown:
1- the beam is in quiet condition and there is no passage of people or any perturbation due to
moving objects, the level is fix . Check that the quiet condition is as described.
2- the beam is disturbed or we are crossing a sensitive area (partial darkening)
3- the beam has been darkened and there is an alarm situation
Point C shows the alarm
threshold (trimmer sens.).
In this case the sensitivity
is adjusted at the half
Point A
(PTP1)
it shows the amplitude
of the signal received
Point C
(PTP3)
it shows the alarm
threshold
Point B
(PTP2)
it shows the quality of
the signal received
C
B
.2 s
0.5 V
.2 s
0.5 V
.2 s
2
.1 V DC
x
10
3
.1 V DC
x
10
0 V
Sensitivity
range
