Autoscale Algorithm - HP 16534A User Reference

Autoscale

Autoscale Algorithm

Autoscale Algorithm
This section describes what the autoscale algorithm does when a signal, or
signals, is present at the oscilloscope inputs. It also describes what occurs
when signals are not present at the oscilloscope inputs.
What the Autoscale Algorithm Does When a Signal is Found
The autoscale algorithm first checks all input channels to determine whether
or not there are any signals present. The vertical scaling is then set as
required for each channel. Next the time base is scaled for a single input
channel. Finally, the trigger channel is selected and the waveforms are
displayed.
Finding the Vertical Settings The autoscale algorithm first checks all
input channels to determine whether or not there are any signals
present. Starting at the lowest numbered channel in the oscilloscope
module, the autoscale algorithm checks for activity on that channel. It
then sets the vertical scaling (V/Div and offset) appropriate to that input
signal. This process is repeated for each input channel. If no activity is
found on an input channel, the original (pre-autoscale) vertical settings
are restored.
When all input signals have been vertically scaled, the time base settings
(s/Div and delay) are scaled. The time base settings are determined based
on the input signal for a single channel.
Finding the Time Base Settings The time base settings (s/Div and
delay) are determined based on the input signal of the lowest numbered
input channel that has been determined to have a signal present.
For example, if signals are present on both channel 1 and channel 2 inputs,
the autoscale algorithm selects the signal on channel 1 input as the time base
scaling source. Similarly, if a signal is present only on the channel 4 input,
then the channel 4 input is selected as the time base scaling source.
The time base is scaled so that between two and five complete cycles of the
source input signal can be seen on the screen. If signals of significantly
different frequencies are probed by the oscilloscope, and the time base
scaling is based on a slow signal, you should be aware of the possibility that
the faster signals may be under-sampled and incorrectly displayed on the
screen.
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