Fluke CombiScope PM3370B User Manual page 171

FUNCTION REFERENCE
PEAK DETECTION
Description:
This function is available only in the digital mode.
In the acquisition system of a Digital Storage Oscilloscope, the sample distance
is determined by the time base speed. At higher time base speeds, the distance
between the samples is short; at lower time base speeds, the sample distance is
longer.
To capture high frequency signals, or signal details of short duration, a high time
base speed is usually selected. A high time base speed captures a time 'window'
that is usually equivalent to the length of the screen. So at higher time base
speeds, the time 'window' is shorter than at lower time base speeds.
Some applications require the time 'window' to be long. This is then achieved by
selecting a slow time base speed, to fit the requirement. But at lower time base
speeds, the time distance between the actual samples increases. The result is,
that signal details shorter than the sample distance will be missed.
The peak detection mode allows the Analog to Digital Convertors (ADC) to
operate at their highest speed, even when a lower time base speed has been
selected. The result is that, even at lower time base speeds, the maximum or
minimum peaks of the signals are placed in memory and displayed. This
technique is referred to as oversampling.
Using peak detection (PEAK DET) allows you to capture peak values of the input
signal which may otherwise occur between the samples. PEAK DET operates on
repetitive signals as well as on signals taken in a single acquisition.
The shortest events (or 'glitches') that can be captured are 5 ns in the single
channel mode and 10 ns in the dual channel mode. Selection of peak detection is
made from the ACQUIRE menu.
The following is an overview of peak detection possibilities:
Mode of use
one channel
two channels
three channels
four channels
Description
any channel
Ch1 & Ch2 or Ch3 & Ch4
ALT mode
CHOP mode
ALT mode
CHOP mode
Peak detection speed
5 ns
10 ns
10 ns
not applicable
10 ns
not applicable
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