Calibration Verification Limits; Example Source Limits Calculation; Example Measure Or Digitize Limits Calculation - Tektronix KEITHLEY SourceMeter 2400 Series Calibration And Adjustment Manual

Section 3: Calibration

Calibration verification limits

Before performing the calibration verification test procedures, you must calculate the calibration
verification limits using the Model 2461 specifications. The most recent version of the specifications is
on the Downloads, Manuals, and Documentation web page
In the Model 2461 Specifications document, source specifications are expressed as a percent of
setting plus voltage, current, or ohms offset. Measure specifications are expressed as a percent of
reading plus voltage, current, or ohms offset.
The calculation for calibration verification limits is:
Specification tolerance = ± [(setting × percent of setting specification) + offset specification
To calculate the calibration verification limits for a range:
1. Select the test setting to verify.
2. Multiply the setting by the percent of setting (for source verification) or percent of reading (for
measure verification) value listed in the specification for that range.
3. Add the absolute value of that calculation to the offset specification for the range.
4. Calculate the low limit by subtracting the result of step 3 from the setting value.
5. Calculate the high limit by adding the result of step 3 to the setting value.

Example source limits calculation

As an example of how source limits are calculated, assume you are testing the 20 V DC range using
a 95 percent of scale signal value, and the Model 2461 one-year accuracy specification.
Use ±(0.015 % of setting + 2.4 mV offset) to get the calculated output limits:
Output limits = 19 V ± [(19 V × 0.015 %) + 2.4 mV]
Output limits = 19 V ± (0.00285 + 0.0024)
Output limits = 19 V ± 0.00525 V
Output limits = 18.99475 V to 19.00525 V

Example measure or digitize limits calculation

When you verify the measure or digitize functions (voltage, current, and resistance), calculate the
upper and lower test limits relative to the reference nominal value determined by the reference
instrument. For voltage and current, the reference nominal value is generally a reading from a
reference digital multimeter (DMM). For resistance, the reference value is the characterized value of
the resistance source.
The calculation of upper and lower test limits is identical to the source limit calculation, except the
reference value is used instead of the nominal setting.
As an example, assume that you are testing the 20 kΩ range, and the actual value of the nominal
19 kΩ calibrator resistor is 19.025 kΩ. Using a one-year normal accuracy specification of ±(0.063 %
of reading + 3 Ω), the recalculated reading limits are:
Specification tolerance = [(19.025 kΩ × 0.063 %) + 3 Ω]
Reading limits = 19.025 kΩ ±(11.99 kΩ + 3 Ω)
Reading limits = 19.025 kΩ ±14.99 Ω
Reading limits = 19.01001 kΩ to 19.03999 kΩ
3-2
Model 2461 Calibration and Adjustment Manual
(http://www.tek.com/downloads).
2461-905-01 Rev. A / February 2016