Keithley 2182, Service Manual, Page: 17 / 120

Verification reading limits
The verification limits stated in this section have been calculated using only the Model 2182
one-year accuracy specifications, and they do not include test equipment uncertainty . If a
particular measurement falls outside the allowable range, recalculate new limits based both on
Model 2182 specifications and corresponding test equipment specifications.
Example limits calculation
As an example of how verification limits are calculated, assume you are testing the 10V DC
voltage range using a 10V input value. Using the Model 2182 10V range one-year accuracy
specification of ±(25ppm of r 2ppm of range), the calculated reading limits are:
Reading limits = 10V ± [(10V
×
25ppm) + (10V
×
2ppm)
Reading limits = 10V
± (250µ
V + 20
µ
V)
Reading limits = 10V ± 270
µ
V
Reading limits = 9.99973 to 10.00027V
Restoring factory defaults
Before performing the verification procedures, restore the instrument to its factory front panel
default conditions as follows:
1. Press SETUP RESTR. The instrument will display the following prompt:
RESTORE: FACT
2. Using either RANGE key, select FACT, then restore the factory default conditions by
pressing ENTER.
NOTE You can use either RANGE key to toggle between FACT and USER setups. Be sure you
use factory defaults for the verification procedures.
Auto-calibration (ACAL)
Before verifying accuracy, perform an auto-calibration to ensure the instrument meets its
specifications. Do the following:
1. Disconnect the test cable from the input jack.
CAUTION
Do not perform full auto-calibration with a test voltage connected to the
input jack, or the instrument may be damaged.
2. Turn on the instrument power, and allow the unit to warm up for at least 2-1/2 hours.
3. Press the ACAL key. The instrument will prompt you as follows:
ACAL: LOW-LVL
1-4 Performance Verification