Keithley 1801, Instruction Manual, Page: 50 / 93

Performance Verification
4-3
4.7 Restoring default conditions
Before performing each performance verification proce-
dure, restore Model 1801 default conditions as follows:
1. From the normal display mode, press the MENU key.
The Model 2001 will display the following:
MAIN MENU
SAVESETUP GPIB CALIBRATION
2. Select SAVESETUP, and press ENTER. The follow-
ing will be displayed:
SETUP MENU
SAVE RESTORE POWERON RESET
3. Select RESET, and press ENTER. The display will
then appear as follows:
RESET ORIGINAL DFLTS
BENCH GPIB
4. Select BENCH, then press ENTER. The following
will be displayed:
RESETTING INSTRUMENT
ENTER to conÞrm; EXIT to abort
5. Press ENTER again to confirm instrument reset. The
instrument will return to normal display, and the
Model 1801 will be enabled.
4.8 Verification procedures
The following paragraphs contain procedures for verify-
ing preamplifier accuracy specifications for the following
measuring functions:
• DC volts
• AC volts
Note that frequency accuracy is a function of the Model
2001 Multimeter and can be verified using the procedure
in the Model 2001 Calibration Manual. Temperature
accuracy is automatically confirmed by verifying the
accuracy of the 2mV DC range, which is used for temper-
ature measurements.
If the Model 1801 is out of specifications and not under
warranty, refer to the calibration procedures in Section 5.
WARNING
The maximum common-mode voltage
(voltage between INPUT LO and
chassis ground) is 41V peak. Exceed-
ing this value may cause a breakdown
in insulation, creating a shock hazard.
4.8.1 DC volts verification
DC voltage accuracy is verified by applying accurate DC
voltages from a calibrator and low-thermal voltage
divider to the Model 2001 input and verifying that the dis-
played readings fall within specified ranges.
Follow the steps below to verify DCV measurement
accuracy.
CAUTION
Do not exceed 1V peak between
INPUT HI and INPUT LO, or pream-
plifier damage may occur. (Inputs
over 2mV will require a one-minute
recovery period.)
1. Connect the DC calibrator and Model 262 Low-
thermal Voltage Divider to the Model 1801 input, as
shown in Figure 4-1.
NOTE
Use only shielded, low-thermal cable
between the low-thermal divider and the
Model 1801 input terminals.
2. Turn on the Model 2001 and the calibrator, and allow
a two-hour warm-up period before making
measurements.
3. Restore Model 1801 factory default conditions, as
explained in paragraph 4.7.
4. Select the Model 1801 20µV DC range.