Trigger - Keithley 595 Instruction Manual

SIN FUNCTION
COEFFICIENTS
/
CENTER READING
Figure 3-6. Coefficients in Filter 2
The coefficients are chosen to approximate the Fourier com-
ponents of a brick wall filter [(sin X)/X]. The passband of
the filter is chosen to pass the signal curve while attenuating
noise outside the passband. Typical white noise reduction
is as follows: Level 1, 1.7; Level 2, 2.5; Level 3, 5.0.
Since the filter is symmetrical, there is a delay between
what is displayed (middle reading) and the measurement
being taken. Filter 0 has a one reading delay, filter 1 has
a two-reading delay, ftiter 2 has a five-reading delay, and
filter 3 has a Breading delay.
If a meter or voltage source parameter is changed, the filter
is "cleared" and starts over. Changes in step~size, delay time,
filter type, trigger mode, voltage limits, voltage souxe, func-
tion and range will restart the filter. (The only parameters
that don't affect filter operation are C/Co, STOREC~;~~Q/t~
and SUPPRESS). The filter is cleared during OL readings
and while zero check is on, for fast reading respon&
Curves plotted with filter 0 will start plotting one reading
after it starts staircasing, filter 1 will begin plotting two
readings later, filter 2 will begin five readings later, and filter
3 wiU begin I3 readings later. Similarly, these filters will
finish early by the same number of readings, leaving an
unplotted region at the end.
3.4.4 Trigger
A "trigger" is a stimulus to the Model 595 to begin a
measurement. Triggering may be done in two basic ways:
continuous or one-shot. In continuous, the stimulus starts
a series of measurements. In one-shot trigger, a single
measurement will be processed each time a trigger stimulus
is received. On power up, the Model 595 is in continuous
trigger and the stimulus is internally generated to start the
measurements.
To access the trigger mode from the front panel, press the
MENU button until the message "triG" appears on the
display. Next to "triG" a 0 or 1 appears. Zero signifies that
the instrument is in continuous trigger and 1 signifies one-
shot trigger. To change trigger functions, press either one
of the voltage source ADJUST buttons to toggle the trigger
mode between 0 and 1. After the desired trigger type-is
displayed, exit from the program by pressing Sm, then
EXIT.
To send the instrument a trigger from the front panel, press
SHIFT. then +I-.
The Model 595 can also respond to other trigger stimuli
besides the button sequence from the front panel. The rear
panel has an external trigger input connector (see
paragraph 3.5.1) and various commands over the IEEE-488
bus can be used as a trigger stimulus (see paragraph 4.9%).
When the filter is first enabled or starts over, there is an
initial reading delay. Each location in the filter is initiaIly
NOTE: The button sequence, SHIFT, +I-, will always
ftied with the fit reading and subsequent readings pass
generate a trigger mess the front panel operation is locked
lout from the IEEE-488 bus.
through the filter. This can be seen on plotted curves.
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