Laboratory manual for the evaluation of non-automatic weighing devices

LG-3.01 Linearity, hysteresis and repeatability at ambient temperature

Table of contents


Reference

Sections 9, 10, 11, 12, 13, and 17 of the Specifications Relating to Non Automatic Weighing Devices (1998)

Application

This test is intended for complete mechanical or electronic weighing devices, indicating and load receiving/weighing elements tested separately.

Settings

Procedure

  1. Pre-condition the device: the DUT must have reached a stable temperature at ambient condition.
  2. Set the device to zero.
  3. Perform a minimum of three increasing and decreasing load tests to capacity using at least 5 known test weights. Loads must be centered on the load receiving element. Loads must be selected in relation to the device capacity, the value of the verification scale interval and the turning points of the tolerances. Determine the true error before rounding (internal or true errors). Record the results.

Multiple range weighing devices

  1. Perform a minimum of three increasing and decreasing load tests using at least 5 known test weights in each individual range. Record the results.
  2. Load the scale to the maximum capacity of the highest range (or manually select the highest range and then load the device to capacity); Remove the load: the indications should return to zero immediately. Switch the device to the lowest range immediately (If the switch over is automatic, the device should have returned to the lowest range automatically). Note the indication near zero at the time the device switches to the lowest range. Observe the weight indication for 5 minutes. Record any changes.

Interpretation of results

Functions

All functions must operate as designed and as intended.

Linearity and hysteresis

Each individual result must be within the tolerance envelope as prescribed by the Non Automatic Weighing Devices Specifications.

Return to zero

The device must return to zero from Max within 0.5e for a complete device, and within 0.35e for an indicating or load receiving/weighing element tested separately.

A multiple range device must return to zero from Max I within 0.5eI. After returning to zero from any load greater than Max1 and immediately after switching to the lowest weighing range, the indication near zero shall not vary by more than 0.5e1 during the following five minutes.

Repeatability

Compare the results for each individual load of increasing and decreasing tests. The maximum difference between the results for the same load must not exceed the in-service

Note 1: The error of any single weighing result must not exceed the maximum limit of error for the given load.

Note 2: A major element (module) tested separately and that is the only component of the weighing system subject to measurement errors due to disturbance or influence factors is allowed entire applicable limits of error (i.e. a weighing element which produces an output digital signal readable by a computer).

Revision

Rev. 1 (March 2010)
  • AZSM renamed to AZTM
  • Formatting changes
Date modified: