IET Labs, Inc. RLC Digibridge 1693, User And Service Manual, Page: 167 / 171

143
1693 RLC Digibridge
Service and Maintenance
5.9.6 Recalibration for Range 1
1. Connect the 95.3-kilohm calibration resistor
to the Digibridge test fixture.
2. Enter the known parameters of the calibration
resistor as in the following example, based
on the values R = 94.986 kilohms and Q =
-280 ppm.
NOTES: The Digibridge will accept six digits for R, even
though only five will be displayed. The Q is associated
with “bin 00”, and its value must be preceded with “-” if
the known Q is negative.)
A. Select ENTER with [FUNCTION] key and
verify that measure mode is CONT.
B. Press [1][=][SHIFT][SPECIAL][1]
C. Press [9][4][.][9][8][6][=][SHIFT][NOM
VALUE]
NOTE: The calibration resistance value should appear
in the left display. The DQ in PPM indicator must be lit.
D. Press [-][2][8][0][=][SHIFT][BIN NO]
[0][0]
NOTE: The calibration Q value should appear in the
right-hand display.
3. Enable and execute the recalibration for this
range as follows. (The following keystrokes
are the same for any range.)
A. Select MEASURE with the [FUNCTION]
key and TRIGGERED with [MEASURE
MODE] key.
B. Press [1][6][9][3][=][l][SHIFT]
[CALIBRATE]
NOTE: The GO indicator being lit and a 6 in the left
and a 6 in the right displays confirm that calibration is
enabled.
C. Press START (The GO indicator remains
unlit while calibration proceeds.)
D. Keeping hands away from the test fixture,
wait until the GO indicator is lit again.
This completes recalibration of one range.
4. Select CONTINUOUS with the [MEASURE
MODE] key and check as follows that
the Digibridge operates properly with the
recalibration.
• The Digibridge should measure the calibration
resistor like any ordinary resistor and display
its Rand Q (ppm) values.
• The Q display can be expected to “jump” a bit.
(precision and repeatability are in the order of
5 ppm).
• The NO-GO indicator will probably be lit; this
is normal.
5. Disconnect the calibration resistor from the
test fixture.
5.9.7 Frequency Calibration
If frequency calibration is not necessary (refer to
“Decision ..., in paragraph 5.8.1), omit the procedures
of paragraph 5.8.7. If necessary at all, these steps
should be done before paragraphs 5.8.2 through 5.8.6.
1. Connect the counter as follows to measure the
period of the test frequency, nominally 1 kHz.
If the Digibridge is not disassembled, provide for a
ground connection as follows. (Otherwise, see NOTE
below.)
A. Insert a 6-32 (1/2 - inch long) screw into
the tapped hole at the right-hand end of the
Digibridge’s test fixture (tighten gently).
B. Connect the ground return of the counter’s
probe to this screw.
C. Insert the short-circuit wire used above
(for example) into the right-hand slot of
the test fixture only.
D. Connect the counter’s probe to this wire.
NOTE: If calibration is being done with the main board
out of the cabinet, a more convenient ground con-
nection is found near the front edge of the board at a
guard-jumper terminal labeled E1 on the board (DUT
CONNECTOR GND on the schematic diagram).
2. Measure the test signal frequency, preferably
as a period and calculate its reciprocal.
For example, if the period is 1.000007 ms, the frequency
is 0.999993 kHz.
3. Calculate the frequency correction “c” (error)
in ppm, as follows.
For example, if the period is 1.000007 ms, the frequency
is 0.999993 kHz.
4. Enter the frequency correction “c” (error)
in ppm, as follows. The allowable range of
entry is -99 to +99.
For example, if the value of “c” is -7 ppm
A. Select ENTER function and press [-] [7]
[=][SHIFT][SPECIAL][0].
Notice that the correction “c” appears in the left display,
followed by a decimal point. The correction has NOT
been entered yet.
B. Confirm the value.
C. Continue the entry process by pressing
[1][6][9][3]
The decimal point should disappear, indicating that the
correction has been entered.
c =
(measured frequency) - 1.000000 kHz
1 kHz
x 1,000,000