Our calibration system considers the system uncertainty for the calculations for “PASS” & “FAIL.” The system uncertainty is explained in detail in the NIST traceability document, which can be provided upon request.
We have included three examples below that use the system uncertainty chart available in the NIST document.
Note: The specification is +/- 0.2 mL/min or 2%, whichever is greater.
Example 1:
The device under test (DUT) measurement is 5.81 mL/min, and the reference flow is 6.004.
The error is 0.194 mL/min.
According to our specification of +/- 0.20 mL/min, it should pass.
The system uncertainty error at 6 mL/min is 0.0202 mL/min.
Subtract the system uncertainty of 0.0202 from the actual flow meter reading of 5.81, giving you 5.7898.
Subtract 5.7898 from 6.004, giving you 0.2142 error.
The measurement is out of specification by 0.0142 mL/min when you add the system uncertainty into the measurement.
Example 2:
The DUT measurement is 10.2 mL/min, and the reference flow is 10.004.
The error is 0.196 mL/min.
According to our specification of +/- 0.20 mL/min, it should pass.
The system uncertainty error at 10 mL/min is 0.0333 mL/min.
Add the system uncertainty of 0.0333 to the actual flow meter reading of 10.2, giving you 10.2333.
Subtract 10.2333 from 10.004, giving you 0.2293 error.
The measurement is out of specification by 0.0293 mL/min when you add the system uncertainty into the measurement.
Example 3:
At 30 mL/min, the specification would be +/- 0.6 mL/min.
In this example, the reading is 30.5 mL/min, and the reference flow is 30.001.
The percentage error is 1.66%.
According to our specification of +/- 2%, it should pass.
The system uncertainty error at 30 mL/min is 0.1023 mL/min.
Add the system uncertainty of 0.1023 to the actual flow meter reading of 3.5, giving you 30.6023.
The measurement is out of specification by 0.0023 mL/min when you add the system uncertainty into the measurement.
