Laboratory manual for the evaluation of non-automatic weighing devices

LG-3.13 Temperature effect on linearity, hysteresis, repeatability

Table of contents


Reference

Sections 9, 10, 11, 12, 13, 17 and 25 of the Specifications Relating to Non Automatic Weighing Devices (1998)

Application

This test is intended for any complete devices and major components (including Analogue to Digital signal converters) incorporating electronic components susceptible to be affected by temperature fluctuations. This test is to be performed also on mechanical scales using temperature compensated springs. The purpose of this test is to ensure that devices are able to measure within applicable limits of error at any temperatures between -10°C to 40°C, unless otherwise marked on the device

Not all devices are affected by all of the influence factors, hence not all influence factor tests need to be performed on all devices. For example, indicating elements that processes only digital information (slave display) do not have to be tested for compliance under influence factors.

Settings

Procedure

For single range or multi-interval weighing devices

  1. If the device has been moved perform the test described in LG-3.21
  2. With the DUT switched "on" and in the environmental chamber, stabilize the DUT at ≈20°C. Monitor the temperature of the DUT until it has reached stability. Wait an additional 2 hours.
  3. Exercise (3 times up to at least 90% Max) the DUT; set the DUT to zero.
  4. Perform at least two increasing and decreasing load tests to capacity using at least five known weights. 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. Record the following data:
    1. time,
    2. temperature,
    3. relative humidity,
    4. loads,
    5. indications,
    6. errors, and
    7. note any malfunctions of the device features.
  5. Repeat the test sequence at -10°C, + 40°C (or at the lowest and highest temperatures marked on the device). Record the following data:
    1. time,
    2. temperature,
    3. relative humidity,
    4. loads,
    5. indications,
    6. errors and
    7. note any malfunctions of the device features.

For multiple range weighing devices

  1. If the device has been moved perform the test described in LG-3.21
  2. Set the device to zero in the lowest range. Perform two increasing and decreasing load tests using at least 5 known weights.
  3. Repeat the test for the other ranges.
  4. 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 to weight indication during the next 5 minutes and record any changes.
  5. Repeat the test sequence at -10°C, + 40°C (or at the lowest and highest temperatures marked on the device). Record the following data:
    1. time,
    2. temperature,
    3. relative humidity,
    4. loads,
    5. indications,
    6. errors and
    7. note any malfunctions of the device features.

Interpretation of results

A multiple range device must return to zero from Maxi within 0.5ei. After returning to zero from any load greater than Max10.5e1.

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

Note: The following tests are grouped and performed in a pre-determined sequence: LG-3.13 Temperature Effect on Linearity, Hysteresis, Repeatability; LG-3.14 Creep and Creep-Return-to-Zero; LG-3.15 Temperature Effect on the No-Load Indication; See the Recommended Test Sequence.

Revision

Rev. 1 (March 2010)
  • AZSM renamed to AZT
  • Test procedure altered to reference LG-3.21
Date modified: