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Field Inspection Manual — Non-Automatic Weighing Devices

Part 3, Section 23: STP-23: Disturbance Test (EMI/RFI, Vibrations)


Sections 29 and 57 of the Non Automatic Weighing Devices Specifications.


To ensure that the scale is adequately protected against environmental factors liable to adversely affect the performance of the device. In particular: vibrations, radio frequency interferences and magnetic field interferences could disturb the scale performance. Scales installed in industrial plants such as paper mills, foundries, mines, grain elevators, and large scales such as vehicle scales, railway scales are more subject to these disturbances.


Ensure that the activation of electrical and electronic equipment is done safely and in compliance with any safety requirements that may prevail.


  • Place a load on the load receptor.
  • Activate any electrical or electronic surrounding equipment susceptible to generate magnetic fields or radio frequencies or other electrical waves (radio transmitter/receiver, transformers, electrical motors).
  • Activate any surrounding equipment that are susceptible to generate vibrations (conveyors, engine of the truck resting on the weighing element).
  • Observe the weight indication.

Interpretation of Results

The difference between the weight indication without the disturbance and the weight indication with the disturbance must not exceed 1 e (one verification interval). In this case, indications do not have to be within the LOE envelope.

Alternatives are:

  • the scale blanks its indications and prevents the printing of values during disturbances (stop working); or
  • the scale provides an error message and prevents the weighing from proceeding during the disturbance; or
  • the scale provides a weight indication that is so completely unstable that it could not be interpreted, or transmitted into memory or to a recording element as a correct measurement value.

Note : the scale must be adequately protected against factors that can adversely affect its performance.


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