Weighing System Installation & Verification Flashcards

What does a 'shift test' or 'corner loading test' evaluate on a platform scale?

Answer: The uniformity of weight indication when a test load is placed at different positions on the platform

A shift test places a known test load at multiple positions (typically 4 corners and center) to verify the scale reads within tolerance regardless of load placement.

During official scale verification, what is the significance of the 'tolerance' value assigned to a weighing device?

Answer: The maximum permissible error the scale may exhibit and still pass verification

Tolerance defines the maximum permissible error (MPE) at any test point; if any error exceeds this value, the device fails verification and must be adjusted or repaired.

What qualification must test weights used for official scale verification possess?

Answer: They must be calibrated and traceable to NIST with documented uncertainty

Verification test weights must have documented calibration with an unbroken chain of traceability to NIST so their true value and measurement uncertainty are known.

What does NTEP (National Type Evaluation Program) approval indicate for a commercial weighing device?

Answer: The device design has been evaluated and found suitable for commercial weighing applications in the US

NTEP is administered by NCWM and certifies that a device type meets NIST Handbook 44 requirements for accuracy and performance in commercial (trade) applications.

What does a 'repeatability test' verify during scale verification?

Answer: That the scale consistently returns the same reading when the same load is applied multiple times

Repeatability testing applies the same test load multiple times (typically three or more) and checks that all readings fall within the maximum permissible error, confirming consistent performance.

How many test positions are typically used when performing a shift (section) test on a rectangular platform scale?

Answer: 5 positions — four quadrant centers and the geometric center

NIST Handbook 44 shift test procedures typically place the test load at five positions: near each of the four corners and at the center of the platform.

What official action must a weights and measures inspector take after a commercial weighing device successfully passes verification?

Answer: Apply an official seal, security tag, or certificate of conformance authorizing commercial use

After a passing verification, an inspector places an official seal or security tag on adjustment access points and issues a certificate, authorizing the device for commercial trade use.