Using Delay; Using User Delay - Keithley 776 Instruction Manual

Depressing the
[VERNIER
fi] push-button after the
usergate is displayed causes an audible alarm to sound.
3. Press the
[CT]
push-button. The Gate light turns off
and the instrument is now ready to perform measure-
ments with an external gate time.
4. Apply an external TTL pulse to the rear panel EXT
INPUT connector. This signal now serves as the ester-
nal gate time. The high level duration of the external
pulse determines the period of the gate time.
5. To exit the User Gate function press the
[VERNIER
u] push-button. Pressing both the
[VERNIER
fi] and
[VERNIER
u] push-buttons presets the displayed gate
time to 1 .O 5.
3-18. Using Delay
The Model 776 has a delay function which inhibits the
closure of the opened gate for a pre-determined period.
This function is very useful in burst measurements.
relay open/close time measurements where bounce time
should be eliminated, and in measurements done on a
train of pulses. The delay function is accessible in PER
A. PLS A. and Time Interval A to B. The delay time ma)
be selected using the following procedure:
1. Set the instrument to [PER
A].
Press the
IDLY]
push-button in the DISPLAY/MODIFY group. Obserw
that the DLY light turns on and that the instrument
displays the delay time.
2. To change the delay time. press the
[VERNIER fi] or
[VERNIER
u] push-buttons. Whenone ofthe ]fi] or [u]
push-buttons are depressed for more than one second.
the instrument increments or decrements continuously.
3. Depressing simultaneously the
[VERNIER
fi] and
the
[VERNIER
u] push-buttons modifies the delay time
to a preset value of 1.0 s.
4. To resume normal display. press the
IDLY]
push-but-
ton. The DLY light turns off. When enabled. the instru-
ment performs measurements with the newly selected
delay time.
5. To enable the delay mode. press the [2nd] push-but-
ton and then the
[DELAY]
(second function to
[GTIDLY])
push-button. Obsewe that the DELAY light
illuminates. This indicates that the instrument is now set
to operate in its delay mode. The delay light turns off
automatically when another function. other than from
those specified above. is selected. Conversely. return-
ing to one of the above functions restores the delay
mode.
6. To return to normal operation depress in sequence the
[2nd] and the
]GT/DLY]
push-buttons. The DELAY
light turns off: indicating that the instrument will no
longer delay the closure of its gale.
NOTE
To prevent operator's error. there is
an internal audible alarm that beeps
whenever a limit is reached. (e.g 100
~5 low limit).
3-19. Using User Delay
The User Delav is useful when a delay time other than
the pre-determined delay times is required. The limits
which must be observed are the minimum limit of 100
ps and the maximum limit of 10.000 s. The User Delay
function is accessible in PER A, PLS A. and Time
Interval A to B operating modes. To operate the instru-
ment in its User Delay mode proceed as follow:
1. Set the instrument to PER A. Press the IDLY] push-
button once. Observe that the DLY light turns on. and
that the instrument displays the delay time.
2. Press and hold the [VERNIER n] push-button and
observe that the display increments. Afler the 100 s
delay time the instrument enters the User Gate mode and
displays the following readout:
USEr dLAY
Depressing the [VERNIER I?] push-button after the
user gate is displayed causes an audible alarm to sound.
3. To resume normal display. press the [DLY] push-but-
ton. The DLY light turns off. When enabled. the inslru-
ment performs measurcmcnts with the user delay time.
4. To enable the user delay mode depress in sequence
the [2nd] and the [DELAY] (second function to
[GT/DLY]) push-buttons. Obsewe that the DELAY
light illuminates. This indicates that the instrument is
now set to operate in its User Delay mode. The delal
light turns off automatically when another function.
other than from those specified above. is selected. Con-
versely. returning to one of the above functions restores
the delay mode.
5. Apply an external TTL pulse to the rear panel EXT
INPUT connector. This signal now senzs as the ester-
nal gate time. Delay is then enabled as long as this input
is kept at TTL high level. The first negative transition
to TTL low disables the delay. The delay is then dis-
abled as long as this input is kept at TTL low level.
3-13