Field Inspection Manual — Non-Automatic Weighing Devices

Part 3, Section 16: STP-16: Repeatability

Reference

Sections 11 and 12 of the Specifications Relating to Non-automatic Weighing Devices (1998).

Purpose

The purpose of this test is to determine if the scale can repeat, within prescribed limits of error, the same indication when the same load is reapplied to the scale several times, in approximately the same manner.

Procedure

Use a test load or test quantity of approximately 25% to 50% Max.

  • Apply the test load to the weighing element and note the indication.
  • Remove the entire load.
  • Repeat this test at least two more times by applying the load to approximately the same area of the weighing element and in the same manner.
  • Note the indications obtained.

Note 1: If several increasing and decreasing load tests are performed, the repeatability of the scale may be determined by comparing the results for each individual load of increasing and decreasing tests.

Note 2: In some cases, 50% Max will not be available or the load may not be placed safely on the device. In these cases, the inspector must use the heaviest load that may be safely loaded on the device to establish repeatability. Every effort should be made to ensure that the load is at least equivalent to the standard requirements for the device type as outlined in Bulletin M-05.

Interpretation of Results

The device meets the requirements if the difference between the results obtained for the same load does not exceed the absolute value of the in-service limits of error for that load.

Each individual result must also be within the prescribed limits of error.

Revisions

The purpose of this revision is to:

  • correct references to Specifications Relating to Non-automatic Weighing Devices (1998).
  • remove reference to eccentricity load being suitable for repeatability testing.
  • recognize that in some cases, specifically tank/hopper and larger capacity devices, 50% Max may not be available for conducting the repeatability test.
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