Keithley 2700, Service Manual

Page: 21 / 174

Performance Verification 1-5
Verification limits
The verification limits stated in this section have been calculated using only the Model 2700
one-year accuracy specifications, and they do not include test equipment uncertainty. If a par-
ticular measurement falls slightly outside the allowable range, recalculate new limits based on
both Model 2700 specifications and pertinent calibration equipment specifications.
Example reading limit calculation
The following is an example of how reading limits have been calculated. Assume you are
testing the 10V DC range using a 10V input value. Using the Model 2700 one-year accuracy
specification for 10V DC of ± (30ppm of r 5ppm of range), the calculated limits are:
Reading limits = 10V ± [(10V
×
30ppm) + (10V
×
5ppm)]
Reading limits = 10V ± (0.0003 + 0.00005)
Reading limits = 10V ± 0.00035V
Reading limits = 9.99965V to 10.00035V
Calculating resistance reading limits
Resistance reading limits must be recalculated based on the actual calibration resistance val-
ues supplied by the equipment manufacturer. Calculations are performed in the same manner as
shown in the preceding example, except, of course, that you should use the actual calibration
resistance values instead of the nominal values when performing your calculations.
For example, assume that you are testing the 10k
Ω
range using an actual 10.03k
Ω
calibra-
tion resistance value. Using Model 2700 one-year 10k
Ω
range accuracy of ± (100ppm of read-
ing + 6ppm of range), the calculated reading limits are:
Reading limits = 10.03k
Ω
± [(10.03k
Ω ×
100ppm) + (10k
Ω ×
6ppm)]
Reading limits = 10.02894k
Ω
to 10.03106k
Ω
Restoring factory defaults
Before performing the verification procedures, restore the instrument to its factory defaults
as follows:
1. Press SHIFT and then SETUP . 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
.