Keithley 194 Instruction Manual page 62

OPERATION
signal during the CRT retrace period. In the CRT mode,
only 100 points will be graphed. However, all samples in
the measurement will be scaled. The output rate is lmsec
per point.
Oscilloscope: The Y axis is used to drive the vertical in-
put while the Z output is used to trigger the oscilloscope.
Only 100 points are displayed in the oscilloscope mode;
a measurement will be scaled in accordance with the scal-
ing factor. Again, the output rate is lmsec per point.
Plotter: The Y and X output are used to drive the Y and
X inputs of the plotter, while the Z output acts as a pen
lift signal. A maximum of 4096 points are graphed in the
plotter mode. If more than 4096 samples are in the
measurement, the instrument will automatically scale it.
Strip Chart: Only the Y output is used in this mode. Each
time a reading is completed, the value will appear at the
Y output and remain at that level until a new reading is
ready. The number of points that can be graphed is equal
to the number of samples in the measurement. Thus, this
mode will give you the best resolution.
NOTES:
The analog output should be left disabled (XY OFF)
when not in use, in order to allow other functions am-
ple microprocessor time to operate normally,
The Model 194 should be placed in the single trigger
mode when using the analog output in order to speed
up XY processing.
In the CRT and oscilloscope modes, analog output alias-
ing can occur if the measurement contains substantial-
ly mnre than 100 samples (the number of points plot-
ted in these two modes). To avoid such aliasing, pro-
gram the unit for no more than 100 samples per
measurement.
3.12.3 Analog Output Data Source (XV DATA)
By using the XY DATA key, you can select the data source
for the analog output. To select the source, you need only
press XY DATA (remember to press SHIFT first) once and
then press uprange or downrange until the appropriate
message is displayed (Table 3-7). The displayed data source
is placed into effect immediate. Press XY DATA again to
return to the previous mode.
Available data sources include:
1. Measurement buffer for the currently selected channel.
2. Readings from the presently selected channel.
3. Entire 64K sampling buffer regardless of measurement
size.
4. IEEE Reading Output Buffer.
Each of these sources is further described below
Measurement Buffer: When this data source is selected,
the measurement for the selected channel will bc placed
in the analog output buffer. If the programmed number
of samples is larger than I'0 (the size of the analog out-
put buffer), and the unit is in the CRT or scope mode, the
measurement will be automatically scaled so that II plot
or screen display reflects all the samples in the mcasure-
ment. If no measurement is available, no data will bc
transmitted.
Channel Readings: Selection of this mode empties the
analog output buffer and allows new readings from the
selected channel to be stored in the buffer as they become
available. As readings become availablt?, tlwv will be
transmitted via the analog output to your graphing device.
In this manner, you could apply a variety of different m,lth
functions to a single measurement and then graph the
results on a single plot.
64K Measurement RAM: This mode graphs the entire 64K
RAM memory regardless of the programmed number of
samples. Thus, all samples plotted by this mode may not
be from the current meaurement. For example, eight XK
sample measurements could be displayed on a single plot.
This data could be from previous single-channel
measurements.
IEEE Reading Output Buffer: The ~100 reading IEEE-488
output buffer that is controlled with the Q command is
the source for the analog output in this mode. Each reading
will reflect the entire associated measurement except for
the waveform mode which only displays the trigger point.
NOTE
For dual A/D channel units, the selected AID channel is
the source for the analog output.
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