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4-106E
4.3.11
ANALOG
'ANALOG
MIN / MAX mode
In this vertical processing mode which can be selected in the time-base positions 5 s/div..5
us/div and in the ROLL
mode, the maximum
and minimum
signa! amplitude over the time
between two adjacent input signal samples is measured by two PEAK DETECTORS per channel.
These maximum and minimum signai levels are applied in serial! toa TRACK AND HOLD gate via
a MULTIPLEXER. This MULTIPLEXER switches between the minimum and maximum
PEAK
DETECTOR output. This resuits in peak values MIN= MAX - MIN - MAX - MIN and so on. The
output values of the TRACK
AND
HOLD gate are applied to the ANALOG
TO
DIGITAL
CONVERTER, converted, stored in the digital trace memory and displayed on the C.R.T. screen.
MAX.
MAX
weuT sienac]_
PEAK
DETECTOR
RESET MAX
MULTI .
TRACK
ANALOG
Prtere
AND
DIGITAL
[ee a
PLEXER
HOLD
CONVERTER)
TRACK
CONVERSION
MIN, | ay
PEAK
a
INPUT SIONAL]
DETECTOR
RESET MIN.
MAT 2451
TRACK:
Figure 4.50 Principle of peak detection.
After the moments that a minimum or a maximum is taken over by the TRACK AND HOLD gate
before the ADC, the relevant PEAK DETECTOR will be reset.
During this reset cycle (about 20 ns) the PEAK DETECTOR is not able to watch the input signal.
of: |g MAX peak detector reacts oninput signal
PSL
MAX peak detector reacts on input signal
Ie!~:1
MIN peak detector ceagtsion input signol
*-]qgMIN. peak detector reogtdh
input
z
.
'signal
>200ns__
j
.
MAX. conversion |
iv conversion .|
MAX. conversion
MIN. conversion -|
RESET MAX. (20ns)
'RESET MIN,20ns)
fe MAX{20ns}
RESET MIN{2Onst
RESET MAX
MAX. toT&H!
{
$
MN to
t
E
:
i
MAT 2452
Figure 4.51 Principle of peak detection.
in the time base setting 5 usec/div the sweeplength is 50 us.
Asweep consists of 250 MIN and 250 MAX samples over 10 divisions. So the time between 2 MAX
samples is 50/250 = 0,2 us = 200 ns. In this 200 ns the PEAK DETECTOR is during 20 ns blind,
due to reset. The blind time ratio is now 10%.
In faster timebase settings, the blind time ratio increases; MIN / MAX can not be used then.
In time base setting 50 us/div, the blind time ratio is 1%.
In time base settings 500 us/div and slower, the blind time ratio is 1°/90
or better.
The MIN
/ MAX
mode can be selected for:
— Glitch detection
~
Envelope
measurements
-
Detection
of the aliasing
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