Keithley 2002 User Manual page 85

Front Panel Operation
The "full" data group should be used for 6.5 digits or greater
resolution. It also allows you to change function, range, or
channel while storing.
COMPACT: With this selection, readings, units, reading
numbers, and status (overflow) are stored. This allows more
readings to be stored in the buffer.
"Compact" is only accurate and displayed to 5.5 digits. It
does not allow changes of function, range, or channel while
storing.
CONTROL
This menu item controls the type of data storage.
FILL-AND-STOP: This control selection fills the buffer
with the requested number of readings and stops. You can
then recall the readings.
PRETRIGGER: This selection continuously stores read-
ings until a user-programmed trigger event occurs. It then
stores post-trigger readings. For example, with a buffer size
of 100 readings, there will be 50 readings stored before the
trigger event and 50 readings stored after the trigger.
The first reading after the trigger is reading zero. Pretrigger
readings have reading numbers and relative time-stamps
with a minus sign; post-trigger readings have reading num-
bers and relative time-stamps with a plus sign.
After selecting PRETRIGGER, configure pretrigger control
further as follows:
• PERCENTAGE or READING-COUNT — Specify the
number of readings to store before the trigger event as a
percentage of the total number of stored readings, or as
a number of pretrigger readings. You will be prompted
to enter the percentage or count value.
• EVENT — Selects the source of the pretrigger or
"mark-point" event. This can be a Manual, GPIB, Trig-
ger Link or External trigger.
CONTINUOUS: With this control selection, readings are
always stored in the buffer. The process continues, with the
oldest readings being overwritten in a circular manner, until
storage is interrupted with the EXIT key.
NEVER: Gets set to this if data storage has been interrupted.
Pressing the STORE key changes NEVER to FILL-AND-
STOP.
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CLEAR-ALL
This action can be used at any time to clear the data buffer of
all stored readings and buffer statistics. Since the MEM1 and
MEM2 memory options are non-volatile, clear-all is the only
way for the operator to clear the reading buffer.
TIMESTAMP
When using FULL data grouping (see DATA-GROUP), a
timestamp is included with each buffer reading. This menu
selection is used to check and/or change the timestamp type
and format.
TYPE: This menu item is used to check and/or change the
timestamp type. Note that changing the timestamp type
clears the buffer.
• RELATIVE-TIME — With this selection, timestamps
are oriented to a timer with the first buffer reading
timestamped at 0.000000 seconds. Each following
timestamp is then based on the currently selected for-
mat (see FORMAT). With the ABSOLUTE format
selected, the timestamp for each reading is referenced
(in seconds) to the first buffer reading. With the DELTA
format selected, each timestamp is referenced (in sec-
onds) to the previous timestamp.
• REAL-TIME — With this selection, timestamps are
oriented to the real-time clock and are based on the cur-
rently selected format (see FORMAT). With the ABSO-
LUTE format selected, each reading is simply
timestamped with the actual time and date. Time can be
expressed in the 12-hour (AM, PM) format or the 24-
hour format (see CLOCK in paragraph 2.12.7).
With the DELTA format selected, the first buffer read-
ing is timestamped at 00000d 00h 00m 00.00s (zero
days, hours, minutes and seconds). Each subsequent
timestamp is referenced (in days, hours, minutes and
seconds) to the previous timestamp.
Timestamp type for buffer readings is coupled to timestamp
type for bus readings. Thus, if you change timestamp type
from this menu structure, it also changes in the MAIN
MENU structure (see TIMESTAMP in paragraph 2.12.7).
FORMAT: This menu item is used to check and/or change
the timestamp format. Note that if format is changed after
readings are stored in the buffer, the timestamps will change
to reflect the alternate format.
• ABSOLUTE — With this selection, each timestamp
provides the time and date that the reading was taken
(see REAL-TIME timestamp type), or the number of
seconds from the first buffer reading that the reading
was taken (see RELATIVE-TIME timestamp type).