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THE CPL PROTOCOL 6 - 39
Definitions
A waveform can be described as a set of two one dimensional arrays: S[1...N]
and T[1...N]. The index n corresponds with the number of the samples and is an
integer value in the range 1...N. The waveform of a sampled signal describes for
a range of sample moments (T[1]...T[N]; usually expressed in seconds) the value
of the signal at these moments (S[1]...S[N]; usually expressed in volts).
A waveform is sometimes expressed in other units. An FFT waveform for example
gives for a range; of frequencies (T[1]...T[N]; expressed in Hz) the signal
amplitude of these frequency components (S[1]...S[N]; expressed in dB). Another
example is the possibility to multiply an input voltage with a floating point value of
another dimension.
Formula’s
S[n] S[n] is the value of sample n, expressed in Y-units.
Y-units are usually expressed in volts.
S[n] = (Yz + (Y[n]
*
Yr))
*
Yu
Sensitivity Usually the sensitivity is expressed in volt/div. In the oscilloscope,
the range of the Y[n] values (Yrng) always equals 2^16 = 65535,
which corresponds with 10.24 divisions on the screen. This gives a
maximum vertical resolution of 6400 ’levels’ per division.
Sensitivity is expressed in Y-units/division.
Sensitivity = 6400
*
Yr
*
Yu/div
Offset Offset is the vertical screen position of the signal ground level,
indicated by "1-" (excluding Y-pos shift). The offset can be adjusted
with the front panel Y POS controls. For calculated traces the offset
can be adjusted with the delta-controls in the MATHematics menu.
Offset is expressed in Y-units (volts).
Offset = -Yz
*
Yu
Note: Traces can also be positioned with the Y-pos control in the
RECALL menu, but this does not affect the offset. The
reason is that Y-pos is a pure display function, which
therefore does not affect the signal sampling, nor the
calculation of a trace using a mathematics function.
T[n] T[n] is the sample moment, expressed in X-units.
X-units are usually expressed in seconds.
T[n] = (Xz + (n-1)
*
Xr) + (dT-corr
*
Xr))
*
Xu