Range A - Keithley 595 Instruction Manual

under test. Therefore, make sure the ZERO CHECK in-
dicator light is on when changing functions or connections.
The ZERO CHECK button toggles the instrument in and
out of zero check.
Zero check is also used with zero correct to cancel internal
offsets in the Model 595 input amplifier. Zero correction
is not applicable to capacitance or Q/t but should be per-
formed for the current function on the 20pA range.
Note that the specifications at the front of this manual
assume that the instrument has been properly zeroed. The
following procedure should be used after the instrument
has warmed up for two hours and repeated as needed every
24 hours or if the ambient temperature changes by more
than PC.
1. Select the current function and the 2OpA range.
2. Press the ZERO CHECK button and be sure the ZERO
CHECK indicator light is on. The Model 595 input
amplifier is now configured to read its own internal
offset.
3. Pr.ess SHfFJ then CORRect to zero correct the instru-
ment. Note that if zero check was not enabled, the zero
correct operation will enable zero check first.
4. The proper range may now be selected and ZERO
CHECK released to make a measurement.
NOTES:
1. Remember to leave zero check enabled when connec-
ting or disconnecting input signals, or when changing
ranges or functions.
2. The zero correct value is stored in permanent memory
and is maintained while the instrument is turned off.
A new zero correct value always replaces an older one.
3.3.6 RANGE A, v
The Model 595 has several ranges available for both
capacitance and current measurements. The capacitance
ranges are 2OpR ZnF and 206 The current ranges are 2OpA,
2OOpA, 2nA, ZOnA,2OOnA, 2pA, 206 and 2004. The in-
strument powers up on the 2OnF capacitance range.
When making a measurement, choose the lowest range
possible without overloading the Model 595. This win maxi-
mize measurement resolution.
The RANGE A, v buttons in the METER block of the
Model 595 allow the user to increment or decrement the
range. The A range button selects the next higher range
and the 'I button selects the next lower range.
WAVEFORM Block
The following controls are found in the WAVEFORk block
of the Model 595 front panel. The SELECT A, v buttons
are used to select the voltage waveform.
The Model 595 is capable of sourcing either DC or a stepped
voltage to the device under test. At power up, the Model
595 is set to measure capacitance, and the waveform is set
to square wave.
OFF CLOV
OFF sets the voltage source to O.OOV iO.OlV. This can be
used to set the voltage source to zero without having to
use the ADJUST buttons. If capacitance is selected, an
"OFF" message will appear on the display since a step is
necessary to measure capacitance.
DC
When DC is selected, the voltage source will output a con-
stant voltage, equal to the voltage source programmed
value. If the capacitance function is selected, the "DC'
message will appear on the display since a step is necessary
to measure capacitance.
STEP
The STEP waveform is the fundamental signal required for
capacitance measurements. Two STEP waveforms are
available: square wave and staircase. The characteristics of
this waveform are tailored using the controls within the
VOIXAGE SOURCE block.
The instrument~powers up with square wave selected.%
is the waveform used to measure capacitance at a specific
test voltage. Refer to Figure 3-4 for a diagram of the
waveform. The voltage starts at VI (set by the user in the
range of -20 to +20 volts). After the programmed delay
3-4