QuadTech 1657 RLC Digibridge Instruction Manual page 22

WARNING
To minimize shock hazard, limit bias to 30 V.
Bias voltage is present at connectors, test
fixtures and on capacitors under test.
Capacitors remain charged after measurement.
Do not leave instrument unattended with bias
applied.
Although special precautions are not required, we recommend the
following procedure, to assure controlled
conditions for both charging and discharging. capacitors.
a. Set the bias voltage to zero.
b. Attach the DUT, with correct polarity.
c. Raise the bias voltage to the specified value.
d. Allowa specified charging and soaking time.
e. Observe and record the specified measurements
(usually Cs and D).
f. Set the bias voltage source to zero.
g. Connect the 10-n discharging circuit.
h. After about 2 s, connect the safety short circuit.
i. Remove the DUT and the discharging circuits.
3.7 CORRECTION FOR TEST FIXTURE ACCESSORIES.
3.7.1 With the Remote Test Fixture.
The remote test fixture, cable assembly, and adaptor (1689-9600,
-9602, -9601) introduce about .001 nF of capacitance in parallel with
the DUT, a generally negligible error. For the best accuracy, select
PARALLEL, C/D, and range 3; measure the capacitance "Cc" with
the remote test fixture open (no DUT). Then measure a DUT, PARALLEL,
C/D; the RLC display is now
Cc + Cx, where Cx is the capacitance of the DUT. Therefore, subtract the
measured Cc from the R LC display to obtain Cx.
3.7.2 With the 1657-9600 Extender Cable (Banana Plugs).
The 1657-9600 extender cable introduces about .0002 nF of capacitance
in parallel with the DUT, a negligible error. For very high precision, the
following procedure can be used,
determining a correction for measurements of parallel capacitance.
Because the physical arrangement and spacing of the cable branches and
connectors is significant, a correction should be determined for each
measurement setup. The following procedure applies to connection with a
precision 3-terminal capacitor, GR 1404 or 1413, for example:
3.8 OPERATION
a. Install an adaptor, GR 874-Q2, on each of the
two coaxial connectors, Land H, of the capacitor.
b. Connect cable branch G to the ground post of the "low" terminal
adaptor. With a clip lead or plain wire, connect this point to the ground post
of the "high" adaptor.
c. Connect cable branch P- to the main post of the
"low" adaptor and stack I- on top of P-.
d. Similarly, connect P+, with I+ stacked on top of it,
to the main post. of the "high" adaptor.
e. Measure this total capacitance, the sum of the desired
measurement and the cable capacitance, Cx + Cc.
f. Carefully lift the stacked pair of cable tips, I+/P+, from the "high"
adaptor and hold them about 0.5 cm (1/4 in.) above the binding post where
they were connected.
Do NOT rearrange the cable branches or change their spacing more than is
absolutely necessary to follow these directions. Hold the plastic tips (not the
wires) and touch the guard (G) circuit firmly with a couple of fingers, to
minimize the
effect of capacitance in your body.
g. Measure the cable capacitance, Cc.
h. Subtract the result of step g from that of step e,
to obtain the desired measurement, Cx.
3.7.3. With the 1688-9600 Extender Cable
("Type 874" Connectors).
The 1688-9600 extender cable introduces no parallel capacitance that can
be resolved on the 1657 Digibridge, if the shielding between "high" and
"low" is maintained consistently. For example, to connect a 3-terminal DUT
having two type 874 connectors, use a type 874 tee for the red and red/white
cables, and another type 874 tee for the black and black/white cables.
3.8 CARE OF DISPLAY PANEL.
Use caution when cleaning the display window, not to scratch it nor to
get clean ing substances into the instrument. Use soft cloth or a ball of
absorbent cotton, moistened with a mild glass cleaner, such as "Windex"
(Drackett Products Co., Cincinnati, Ohio). Do NOT use a paper towel; do
NOT use enough liquid to drip or run.
If it should be necessary to place marks on the window, use paper-based
masking tape (NOT any kind of marking pen, which could be abrasive or
react chemically with the plastic). To minimize retention of any gummy
residue, remove the tape within a few weeks.