Line Power; Recommended Calibration Equipment; Offset Adjustments - Keithley 1801 Instruction Manual

Service Information
The calibration equipment should also be allowed to
warm up for the minimum period specified by the
manufacturer.

5.2.3 Line power

The Model 1801 should be calibrated while the Model
2001 is operating from a line voltage in the range of
90-134V or 180-250V at 50, 60, or 400Hz.

5.2.4 Recommended calibration equipment

Table 5-1 lists all test equipment recommended for cali-
bration. Alternate equipment may be used as long as that
equipment has specifications at least as good as those
listed in the table.

5.2.5 Offset adjustments

The following procedure to null offsets must be per-
formed before performing the normal calibration proce-
dure covered in paragraph 5.2.6. The basic procedure for
nulling offsets is as follows:
1. Clean the input terminals, then connect the low-
thermal shorting strap to the INPUTS terminals, as
Table 5-1
Recommended equipment for calibration
Mfg. Model
Fluke 5700A
Keithley 262
Keithley 1507
Keithley
Keithley Part # R-336-10K
* 90-day calibrator specifications shown include total uncertainty at specified output. Model 262 specifications are for
one year.
** Low-thermal shorting strap is supplied with the Model 1801.
***Remove plating from leads before use.
5-2
shown in Figure 5-1. Note that Figure 5-1 also shows
the location of the voltage offset control (V ZERO).
2. Make certain the preamplifier module is installed in
the thermal isolation enclosure. Remove the lid only
while making adjustments.
3. Turn on the Model 2001 power, and make sure the
preamplifier is enabled as follows:
A. Press the CHAN key.
B. Select CONTROL, then press ENTER.
C. Select ENABLE, then press ENTER.
4. Select the 20µV DC range, and allow a two-hour
warm-up period before proceeding with the offset
adjustments.
5. Select the slow response filter as follows:
A. Press CHAN.
B. Select FILTER, then press ENTER.
C. Select SLOW, then press ENTER.
D. Press EXIT to return to normal display.
6. Adjust the voltage offset control (V ZERO) for a
Model 2001 front panel reading of 0µV ± 0.001µV.
7. Enable the REL mode to null any remaining offset.
8. Disconnect the low-thermal shorting strap from the
INPUTS terminals, and connect the 10k Ω low-
thermal resistor to the INPUTS terminals, as shown
in Figure 5-2. (For best results, remove the lead
plating before use.) Note that the offset current
adjustment control (I ZERO) is also shown in Figure
5-2.
Description
Calibrator
Low-thermal Voltage Divider
Low-thermal Cable
Low-thermal Shorting Strap**
Low-thermal Resistor***
Specifications*
0.2V DC: ±11ppm
2
10 : 1, ±35ppm
3
10 : 1, ±35ppm
4
10 : 1, ±100ppm
10kΩ, ±5%