Keithley 263 Instruction Manual page 141

A. Volts Calibration
NOTE
The first ("cold'~ calibration of the volts and ohms
sources must be performed in less than 40
minutes.
1. Add the calibration program to the Model 263 menu
by holding in the OPERATE button while turning the
instrument on. Do not release the OI'ERXE button
until the display blanks.
2. While waiting for the Model 263 to warm up for five
minutes, connect the Model 263 to the Model 196
System Dh4M as shown in Figure 8-3.
3. While in standby, program the Model 263 for 1901MOmV
and set the Model 196 DMM to the 300mV range.
4. On the Model 263, press ZERO and then OPERATE
to source OO.OOOmV to the DMM.
5. On the DMM, the offset of the Model 263 and the
DMM will be displayed. To zero the display, thus
cancelling the offset, press the ZERO button on the
DMM.
NOTE
If using a DMM that does not have a zero suppress
feature, record the offset reading. This value will
have to be algebraically subtracted from the
reading in the next step to determine the actual
voltage sourced by the Model 263.
6. Press ZERO on the Model 263 to sowe the pro-
grammed voltage to the DMM. The reading on the
DMM is the voltage sourced by the Model 263.
7. Record the output voltage value in Table 8-3 ("cold" cal)
or Table 8-6 ("hot" cal).
8. The calibration value is derived from the output value
as follows:
A. The least significant digit (LSD) of the Model 263
display can only be programmed as a five or as a.
zero. Thus, the LSD of the calibration value has to
be rounded to a five or zero. If the LSD of the 5%
digit output value is a one or two, replace it with
a zero. For example, if the output value is 190.142mV,
the calibration value will be 190.14OmV. If the LSD
of the output value is three through
seven,
replace
it with a five. For example, if the output value is
189.877mV, the calibration value will be 189.875mV.
If the LSD of the DMM reading is an eight or nine,
change it to a zero and increment the next highest
digit by one unit. For example, if the output value
is l89,878mV, the calibration value will be X39.8801+.
8. Record the calibration value in the Table 8-3 ("cold"
cal) or in Table &6 ("hot" cal).
9. Select the Model 263 calibration program as follows:
A. r?reL;he MENU button to display the message
I,
8. Release the MENU button. The exponent decimal
points will turn on (not flashing) to indicate that the
calibration program has been selected. Also, the cur-
sor position is indicated by a flashing digit segment.
10. Using the adjust method, enter the calibration value
on the display of the Model 263. The CURSOR buttons
move the display cursor right and left, while the AD-
JUST buttons increment and decrement the display
reading at the selected digit. Note that KEYPAD is in-
operative while in the calibration program.
11. Calibrate the range by again pressing MENU. If the
calibration switch is in the enable position the message
"Stor" will be briefly displayed to indicate that the
calibration constant was stored in NVRAM. If the
message "out" is instead displayed followed by flashing
exponent decimal points, then the calibration switch
is in the disable position and calibration constants will
be lost when the instnunent is turned off. See
paragraph 8.4.6 to set the calibration switch.
Note: If there is no message ("Stox" or "out") briefly
displayed when attempting to enter a calibration value,
a problem exists and calibration will not occur. Also,
flashing exponent decimal points with the calibration
switch in the enabled position indicates a problem.
Refer to paragraph 8.7 for servicing information.
IZ. Place the Model 263 in standby and disable the zero
feature on the DMM.
W. Using Table 8-3 ("cold" cal) or Table 8-6 ("hot" cal) as
a guide, repeat steps 3 through 12 for the 2V and 2W
ranges.
8-4