Keithley SourceMeter 3A 2420, Service Manual

Page: 34 / 136

2-4 Calibration
*90-day, full-range accuracy specifications of ranges required for various measurement points.
** Necessary for calibration of 3A current range. Resistor must be characterized to ±300ppm or better using recom-
mended DMM before calibrating 3A range.
1
Ω
resistor characterization
The 1
Ω
resistor must be characterized to ±300ppm or better before calibrating the 3A current
range. Use the 4-wire ohms function of the DMM recommended in Table 1-1 to measure the re-
sistance value, and then use that measured value to calculate the current during the 3A current
range calibration procedure.
Unlocking calibration
Before performing calibration, you must first unlock calibration by entering or sending the
calibration password as explained in the following paragraphs.
Unlocking calibration from the front panel
1. Press the MENU key, and then choose CAL, and press ENTER. The instrument will dis-
play the following:
CALIBRATION
UNLOCK EXECUTE VIEW-DATES
SAVE LOCK CHANGE-PASSWORD
2. Select UNLOCK, and then press ENTER. The instrument will display the following:
PASSWORD:
Use , , , , ENTER or EXIT.
3. Use the up and down RANGE keys to select the letter or number, and use the left and
right arrow keys to choose the position. (Press down RANGE for letters; up RANGE for
numbers.) Enter the present password on the display. (Front panel default: 002420.)
Table 2-1
Recommended calibration equipment
Description Manufacturer/Model Specifications
Digital Multimeter Hewlett Packard
HP3458A DC Voltage*
DC Current*
1V:
10V:
100V
10
µ
A:
100
µ
A:
1mA:
10mA:
100mA:
1A:
±5.6ppm
±4.3ppm
±6.3ppm
±25ppm
±23ppm
±20ppm
±20ppm
±35ppm
±110ppm
Precision Resistor** Isotec RUG-Z-1R00-0.1 1
Ω
, ±0.1%, 100W