Maintenance
7-8
Procedure:
1. With the power off, connect the Models 263 and 6512 to
the GPIB interface of the computer.
2. With the power off, connect the Model 263 to the Model
6512, as shown in Figure 7-3. Also connect the external
voltage calibrator to the Model 263, as shown in Figure
7-4.
3. Turn on the Models 6512 and 263, and the external volt-
age calibrator, and allow a two-hour warm-up period be-
fore beginning calibration.
4. Set the IEEE-488 primary address of the Model 263 to
8, and set the primary address of the Model 6512 to 27.
5. Enter the calibration program into the computer. (See
Appendix D for complete details.)
6. To calibrate the instrument, run the program, and follow
the instructions on the CRT display.
7. After all functions are calibrated, the program will
prompt for permanent storage of calibration constants in
NVRAM. This feature allows you to stop at this point in
order to avoid permanent calibration. Unless calibration
is made permanent, the calibration constants will be lost
when the instrument is turned off.
8. If selected, storage of calibration constants into
NVRAM is performed as indicated by the “Stor” mes-
sage on the Model 6512. If instead the message “out” is
displayed, the calibration jumper is in the disable posi-
tion, and calibration constants will be lost when the
Model 6512 is turned off. (See paragraph 7.4.3 for infor-
mation on the calibration jumper.)
7.4.16 Additional calibration points
The electrometer calibration points discussed in the preced-
ing paragraphs were chosen to optimize instrument accuracy
without making the calibration procedure overly tedious and
time consuming. As noted earlier, these calibration points are
permanently stored in NVRAM when the correct storage se-
quence is performed.
Although this calibration method is more than adequate to
allow the instrument to meet or exceed specifications, it is
possible to temporarily calibrate those ranges not directly
calibrated as part of the calibration procedure (for example,
certain amps ranges or the external feedback function). With
the calibration jumper in the disabled position, place the in-
strument in the desired function, and select the range to be
calibrated. Apply the necessary calibration signal, and enter
that value into the instrument’s memory, either with the front
panel calibration program, or over the IEEE-488 bus (The
flashing exponent decimal points will indicate parameters
have been entered). The nominal adjustment range is ±6%
(±12% in external feedback). However, it is important to note
that such calibration will be only temporary as these param-
eters will be lost when the power is turned off. Under these
conditions, the instrument will revert to calibration constants
previously stored in NVRAM the next time it is turned on.
Note that the IEEE-488 DCL and SDC commands will also
cancel temporary calibration constants.
As an example of this procedure, let us assume that you wish
to temporarily calibrate the 2mA range–a range that is not
part of the normal calibration sequence. The following basic
procedure could be used to calibrate this range.
1. Select the amps mode, and place the instrument on the
2mA range.
2. Zero correct the instrument by enabling zero check and
then zero correct in that order.
3. Connect a suitable calibration signal to the instrument.
Typically, calibration is done at 95% of full range, or
1.9000mA in this case.
4. Disable zero check, and enter the front panel calibration
program, as described in paragraph 7.4.9. The instru-
ment will then display a reading that reflects its present
calibration point for the selected range. The exact point
can be set by using the ADJUST buttons to set the dis-
played value to exactly 1.9000mA.
5. After all points have been calibrated, exit the program
by pressing SHIFT then SELECT.
6. If bus calibration is desired instead, send the calibration
signal over the bus. In this case the command would be:
A1.9E-3X.
7. Any non-standard calibration points will be only tempo-
rary, as stated earlier.
7.5
Special handling of static-sensitive
devices
CMOS devices operate at very high impedance levels for low
power consumption. As a result, any static charge that builds
up on your person or clothing may be sufficient to destroy
these devices if they are not handled properly. When han-
dling these devices, use the precautions below to avoid dam-
aging them.
Summary of Contents for 6512
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