Setting Input Condition Controls - Keithley 776 Instruction Manual

lights illuminate, reset the counter using the software
reset procedure which is described in paragraph 3-5.
2. Press the ]TL A] push-button. Observe that the TL A
and VOLTS indicators turn on and that the display reads
as follows:
0.00
This reading indicates the selected trigger level in
units of volts.
3. To set a positive trigger level press the [VERNIER
fi] push-button. Holding in the [I?] or [u] push-buttons
for more than I second. causes the instrument to incre-
ment or decrement continuously. To set a negati\:e trig-
ger level press the [VERNIER u] push-button until the
desired level has been reached.
NOTE
Pressing the [VERNIER fl] or [VER-
NIERU] push-buttons. when the lim-
its of +5.00 or -5.00 respectively have
been reached. causes
an
audible
alarm to sound.
4. Simultaneously press the two [VERNIER] push-but-
tons and note that the display reading resets to 0.00.
5. Press the [TL A] push-button. The indicator light
turns off and the instrument returns to its previous
measurement state.
6. To set the trigger level for both Channels A and B.
select a function which involves both inputs (eg ratio
A/B. Phase A to B. time intenjal A to B or totalize B by
A). Pressing the [TL] push-button once turns the TL A
light on: indicating that the instrument displays the
trigger level for Channel A. A second consecutive press
turns the TL B light on: indicating that the instrument
displays the trigger level for Channel B. A third push
turns TL B light off. The instrument then resumes its
normal operation.
3-11. Setting Input Conditioning
Controls
A proper set-up of the input controls ensures proper
operation of the instrument. There are five push-buttons
which control the input. These push-buttons are com-
mon to both Channels A and B.
Changing one of the input setting controls is simply
a matter of pressing the required push-button. There are
5 lights for each input channel which are associated with
each of the five controls.
To set input condition controls for Channel A pro-
ceed as follows:
1. Set the instrument to operate al one of the following
functions: FRQ A. PER A. PLS A. or V Peak A.
2. To select the required coupling mode press the [AC]
push-button. Instrument is dc coupled when the AC
light is off. When the AC light is on the instrument is
ac coupled.
3. To change the slope that the instrument will trigger
on. press the [SLOPE] push-button. The counter trig-
gers on a positive going edge if the slope light is off. If
the slope light is on the counter triggers on a negative
going edge.
4. Attenuation is required when the inpur signal exceeds
the specified dynamic range. To attenuate the signal
press the [x10] push-button, The input signal is allenu-
ated by a factor of 10 when the x10 light is on. When
the x10 light is off. the input signal is not attenuated.
5. In low frequency applications. where the frequency
range is below 100 KHz. it is recommended to use the
low pass filter. The low pass filter attenuales the high
frequency components which may interfere with the
required measurement. To apply a low pass filter press
the [LPF] push-button. High frequency signals are fil-
tered when the LPF light is on. The filter is deactivate
when the LPF light is off.
6. In high frequency applications above 1 MHz. or high
slew rate signals. it is rccommcnded that the input cable
be terminated with 50 R at the counter end. To change
the input impedance from 1 Mn to 50 n press the 150
n] push-button. Input is termination with 50 0 when
the SO Cl light is on Input impedance is I MCI when the
50 0 light is off.
To set input condition controls for Channel B pro-
ceed as follows:
1. Set the instrument to operate in one of the following
functions: FRQ B or TOT B.
2. Use the same procedure as described above for Chan-
nel A.
To set input condition controls for both Channcl~ A
and B proceed as follows:
1. Set the instrument to operate in one of the following
functions: Time Interval A IO B. Ratio FRQ/B. Phase A
to B. TOT B by A. or TOT B by AA.
2. To select the AC coupling mode for Channel A. press
the
[AC]
push-button once. The AC A lighl illuminates:
3-9