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Theoretical Introduction
OSCILLOSCOPES
Digital oscilloscope
DEFINITION:
■ Digital oscilloscope
This instrument that allows you view the waveform
of periodic electrical signal (even very slow) a
function time, view single event. practice, the oscilloscope must sample frequency least times higher than the presumed
frequency this signal.
The "useful bandwidth" will one tenth the maximum sampling rate and will expressed MegaHertz. Because the
processing digital, signals and automatic measurements
can stored and the data can transferred onto a
computer. This interval
determines the "horizontal resolution".metrix.fr
.
"Equivalent time" sampling can used achieve much
higher "sampling frequencies" because the samples are
taken from several successive sweeps. The vertical resolution defined the
capacity bits the Analogue/Digital Converter (ADC).
Choosing your digital oscilloscope
■ Sampling:
Operation that involves measuring the instantaneous value signal's amplitude regular intervals.
An instrument with times more storage capacity allows
you sample times more frequently for given
recording duration.
■Memory depth:
This expressed kilo points (kpoints) and determines
the "recording duration" according the sweep speed;
the higher is, the longer the "recording duration" will be.
■Sampling frequency:
The inverse the sampling interval, this expressed MegaSamples per second (MS/s).
■Sampling modes:
For "real-time" "one-shot" sampling, all the samples are
acquired single sweep. This mode is
reserved for periodic signals.4% for 8-bit ADC (28=256)
■Signal processing:
Particularly useful mathematical operations between signals: +,-,* and even complex functions (Fast Fourier
Transform (FFT), harmonic analysis, etc.
According "Shannon's theorem", this frequency must least double the frequency the signal be
observed.
■Vertical resolution:
"Quantization" involves converting sample's value into binary number. varies function of
the sweep speed.)
Sampling
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Block diagram digital oscilloscope
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Detailed product brochures can downloaded from www. 1/256 0
