Q/T Verification; Capacitance Verification - Keithley 595 Instruction Manual

PERFOUMANCE VERIFICATION
6.5.3 Q/t Verification
ced~re to-determine the capacitsnce limits for the character-
ized capacitors:
Perfvrm the following steps to verify Q/t:
1. Using a pencil, record the reported lkHr values of the
1. Place the Model 595 in the capacitance function, 2nF
Model 5955 characterized capacitors in Table 6-3 in the
range, set-delay time to one second, steps voltage to O,lv
cohnn labeled "R&ported Capacitance Value". The
squarewave, and then select the Q/t display.
~~~ ~nomhial values of the capacitors are in parenthesis.
2. With a capped input, verify that the display reads .OOOO 2. To determine the aIlo?able readings, complete the table
ml a2 counts.
be performing the indicated mathematical operations.
3. Using the techniques used to verify the ZOOpA current
3. Transfer the calculated allowable readings to Table 6-4.
range (see previous paragraph), apply 19OpA to METER
DmJT.
4. Verify that the display reads .1900 nA 521 counts.
After determing the capacitance limits, the capacitance
5. Reverse the polarity of the current source and verify that
verification procedure can be performed. Using Table 6-4
the display reads -.1900 nA &21 counts.
as a guide, perform the following procedure to verify
capacitance:
6.5.4 Capacitance Verification
Capacitance verification consists of connecting capacitors
with known measured values to the input and checking
that the readings are within allowable limits. The Model
5955 is a set Of characterized (measured) capacitors that can
be used for verification Before using the capacitors, make
sure that the data for re-characterization has not passed.
The characterization procedure for the Model 5955 can be
found in its instruction manual.
The capacitance Iimits used for verification are derived from
6. Repeat the above basic procedure for the rest of the range
the accuracy specifictions applied to the actual (not nomi-
entries in Table~6-4. Each table entry defines the instru-
nal) values of the capacitors. Thus, the capacitance limits
ment setup (RANGE, FIUER, STEP V, delay), input and
must be calculated bv the technician. Table 6-3 is urovided
allowable reading.
1. Place the Model 595 in the following state: Capacitance
function, 2OnF range, fdter 2, OO.lOV squarewave step
voltage, and 00.20 second delay.
2. Place the supplied cap on the METER INPUT connector.
3. Disable ZERO CHECK (if on) and enable SUPPRESS if
thedisplay is not zeroed.
4. Remove the cap and connect the 'l&F (nominal) capa-
citor directly (no cables) to the METER INPUT and
VOLTAGE SOURCE OUTPUT ?onn&tors of the
instrument.
5. Verify that the reading is within the range of readings
recorded in the table.
to simplify these c&ulations. Perform the foIlo&ng pro-
Table 6-3. Determining Capacitance Limits
Range
2onF
(18nF)
20&
W3nF)
2nF (1.8n.F)
2nF (1.8nF)
ZOOpF* (18OpF)
2OOpFf (l80pF)
zooPF** (18opF)
?OOpF" (18OpF)
*For Step V of OO.lOV.
*For Step V of OO.lOV.
.~~
Allowable Readings
Reported
Capacitance
Value Mininmm Maximum
x 0.994 =
i ~0.cmnF =
x 1.006 =
+ 0.002nF =
x 0.992 = - 0.0002nF =
x 1.008 = ~~ + o.ooo2nF =
X~~ 0.99 =~~ - OO.lOpF =
x 1.01 = ~+ OO.lOpF =
x 0.99 = - 00.2OpF =
x 1.01 = ~+ 00.2OpF =
6-6
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