Keithley 194 Instruction Manual page 43

OPERATION
If a numeric key is pressed instead of a cursor key im-
mediately upon entering the data entry mode, the current
value is blanked out and the new value must be keyed in
completely.
The type of units that will be entered will depend on the
selected mode-some modes require voltage units, while
others require time/frequency information. For example,
a trigger level is entered as a voltage, thus appropriate units
(mV or V) are automatically selected by pressing one of
those two keys. In a mode such as samples, frequency
(MHz, kHz, or Hz) or time interval (ps, ms, or s) units arc
selected with the aid of the FREQiTIME key, as discussed
below.
NOTE
Pressing a units key automatically enters data. +/-
may be pressed at any time during the numeric
input sequence.
3.4.2 ENTER
The ENTER key performs the last step in the data entry
process. Once you have keyed in the desired numeric data,
pressing ENTER will store the parameter in question in
memory for use by the instrument, unless an invalid
parameter was entered. If data is not valid, the instrument
will display one of the following error messages:
NMBR TOO LARGE
Or,
NMBR TOO SMALL
The instrument will then return to the data entry mode.
If the data is valid, pressing ENTER will cause the instru-
ment to momentarily display the entered value, and then
return to the previous operating mode. If a units key is
pressed during the data entry process, ENTER need not
be used.
ENTER is also used to store instrument configurations
when using the setup mode, as discussed in paragraph
3.16.
3.4.3 CANCEL
The CANCEL key can be used during the data entry pro-
cess to
cancel
data previously entered into the display with
3-4
the data entry keys. When CANCEL is pressed, the display
will return to the previous value. If no cursor or data en-
try keys were pressed, the unit will return to the previous
mode.
Pressing CANCEL after pressing ENTER has no effect
since the value is already stored in memory.
3.4.4 FREWTIME
FREQiTIME is used in the data entry mode to toggle be-
tween reciprocal frequency time units when programm-
ing the following modes: sample rate, number of samples
per measurement and delay.
When FREQiTlME is used to program sample rate, it tog-
gles the displayed value between samples (or scan se-
quence, for the scanner) per second in Hz, kHr, or MHz,
and time interval between samples in xc, msec, or psec.
When programming samples per
measurement,
FREQiTlME toggles units between elapsed time for the en-
tire measurement in set, msec, or usec, and the number
of samples per measurement.
When programming trigger delay, the FREQiTlME key tog-
gles data entry units between time in set, msec, or psec,
and the total number of samples.
NOTE
Once the data
entry
keystroke sequence has
begun, FREQiTIME will have no effect.
3.4.5 Using the Cursor Keys
During the numeric entry process, the left (4.) and right
(A )) cursor keys can be used to move the cursor (flashing
digit or segment) to the desired display digit location. Once
the cursor is on the desired digit, a new value can be typed
in; the change will affect only the location where the
change is made. In this manner, a one or two digit change
can be made easily without having to type in the new value
completely.
If a numeric key is pressed first during the entry process
without pressing a cursor key first, the current value is
blanked out and the complete number must be keyed in.