Top And Base Voltages - HP 1652B Getting Started Manual

Top and Base
Voltages
All measurements except Vpg are calculated using the Vtop (100%
voltage) and Vbase (0% voltage) levels of the displayed waveform. The
Vtop and Vbase levels are determined from an occurrence density
histogram of the data points displayed on screen.
The digitizing oscilloscope displays 6-bit vertical voltage resolution.
This means the vertical display is divided up into 64 voltage levels.
Each of these
64
levels is called a quantization level. Each waveform
has a minimum of 500 data points displayed horizontally on screen.
Each of these data point sets have one quantization level assigned to it.
The histogram is calculated by adding the number of occurrences of
each quantization level of the displayed data point sets on the displayed
waveform.
The quantization level with the greatest number of occurrences in the
top half of the waveform corresponds to the Vtop level. The
quantization level with the greatest number of occurrences in the
bottom half of the waveform corresponds to the Vbase level.
If Vtop and Vbase do not contain at least 5% of the minimum (500)
data points displayed on screen, Vtop defaults to the maximum voltage
(Vmaximum) and Vbase defaults to the minimum voltage (Vminimum)
found on the display. An example of this case would be measurements
made on sine or triangle waves.
From this information the instrument can determine the
10,50,
and
90% points, which are used in most automatic measurements. The
Vtop or Vbase of the waveform is not necessarily the maximum or
minimum voltage present on the waveform. If a pulse has a slight
amount of overshoot, it would be wrong to select the highest peak of
the waveform as the top since the waveform normally rests below the
perturbation.
Automatic Measurement Algorithms
HP 16528/1653B
B-2
Front-Panel Reference
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