TS–024 When an auxiliary (peripheral) device is fitted to a weighing instrument

This policy confirms the accuracy and suitability requirements of the printed and stored information generated from an approved weighing instrument. This scope only applies to the auxiliary equipment that has been retrofitted to an approved instrument.


  • For a given load there must be no difference between the indications of the primary display and of the printing or storage device connected directly to the approved weighing instrument (i.e. must have the same value, decimal place and units of measurement)
  • The figures, units and designations forming the primary indications from the printer must be of a size, shape and clarity for reading to be easy.
  • All displaying, printing and tare weighing devices of an instrument shall, within any one weighing range, have the same scale interval for any given load.
  • If a secondary display is required to meet the conditions of the approval certificate, such as in certain weighbridge installations to provide a clear view for the operator/customer, then a suitable secondary display must be installed and made available prior to carrying out a verification/inspection testing.
  • Indications other than primary indications may be printed provided that they do not lead to any ambiguity in regard to the primary indications;
  • The measurement data recorded or displayed on an auxiliary device may only deviate from the data displayed on the primary indicator for the purpose of meeting the legal requirements of the Weights and Measures Act 1987 or Weights and Measures Regulations 1999 i.e. a deduction from the indicated or gross weight has been made to allow for the weight of the tare value or the packing material. In this instance the recorded or displayed value must include and identify;
    • the true net weight of the goods, and
    • the weight of the tare value or packing material.

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The mathematical sum of the true net weight and the tare value must be equal to the gross weight indicated on the primary indicator (all three values must have the same verification scale interval ‘e’). 

  • If a transaction performed by the instrument is printed, for example: weight value, unit price or price to pay, the printed information shall be checked in conjunction with any verification or on- inspection tests completed on the weighing instrument. In the situation where a NAWI is connected to a printing device post examination, then an Accredited Person will return to confirm that the records generated by the newly installed printer are accurate and update the previous test record.
  • In a self-service arrangement (e.g. unmanned weighbridge), generally the following additional auxiliary equipment may be provided;
    • Printing device - for issuing a customer receipt and
    • Other auxiliary devices for registering measurement data for the benefit of the supplier.
  • The records obtained and retained from both the above devices shall be checked in conjunction with any verification and on- inspection tests performed on the measuring instrument.
  • Printing shall be clear and permanent for the intended use;
  • The printed information must meet Clause 4.6.11 of OIML R76, as detailed below:

4.6.11 Printing of weighing results

Gross weight values may be printed without any designation. For a designation by a symbol, only “G” or “B” are permitted.

If only net weight values are printed without corresponding gross or tare values, they may be printed without any designation. A symbol for designation shall be “N”. This applies also where semiautomatic zero setting and semi-automatic tare balancing are initiated by the same key.

Gross, net, or tare values determined by a multiple range instrument or by a multi-interval instrument need not be marked by a special designation referring to the (partial) weighing range.

If net weight values are printed together with the corresponding gross and/or tare values, the net and tare values shall at least be identified by the corresponding symbols “N” and “T”.

However, it is permitted to replace “G”, “B”, “N” and “T” by complete words in an official language of the country where the instrument is used.

If net weight values and tare values determined by different tare devices are printed separately, they shall be suitably identified.

When gross, net and tare values are printed together, one of these values may be calculated from two actual determinations of mass. In the case of a multi-interval instrument the calculated weight value may be printed with a smaller scale interval.

The printout of a calculated weight value shall be clearly identified. This should preferably be done by the symbol “C” in addition to the symbol mentioned above if applicable or by complete words in an official language of the country where the instrument is used.

  • If transactions performed by the instrument are printed, for example: weight value, unit price or price to pay, they shall be printed.
  • The data storage devices must meet Section 5.5.3 of OIML R76 as detailed below:

5.5.3 Data storage devices (DSD)

If there is a device, whether incorporated in the instrument or being part of the instrument as software solution or connected to it externally, that is intended to be used for long-term storage of weighing data (in the sense of T.2.8.5), the following additional requirements apply. The DSD must have a storage capacity which is sufficient for the intended purpose.

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Regulation of the minimum duration for keeping information is outside the scope of this recommendation and is probably left to national trade regulations. It is the responsibility of the owner of the instrument to have an instrument that has sufficient storage capacity to fulfill the requirements of his activity. Type examination will only check that the data are stored and retrieved correctly, and that there are adequate means provided to prevent the loss of data if the storage capacity is exhausted before the foreseen duration. The legally relevant data stored must include all relevant information necessary to recall an earlier weighing.

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Legally relevant data are (see also T.2.8.1):

  • gross or net values and tare values (if applicable, together with a distinction of tare and preset tare);
  • the decimal sign(s);
  • measurement unit(s) (may be encoded);
  • identification of the data stored;
  • the identification number of the instrument or load receptor if several instruments or load receptors are connected to the data storage device; and ƒ
  • a checksum or other signature of the data stored. The legally relevant data stored shall be adequately protected against accidental or intentional changes. The legally relevant data stored shall be capable of being identified and displayed, where the identification number(s) shall be stored for later use and recorded on the official transaction medium. In case of a printout the identification number(s) shall be printed. The legally relevant data shall be stored automatically.

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This requirement means that the storing function must not depend on the decision of the operating person. It is accepted, however, if intermediate weighings that are not used for the transaction are not stored. Stored legally relevant data sets which are to be verified by means of the identification must be displayed or printed on a device subject to legal control. DSDs are identified as a feature, option, or parameter on OIML Certificates if they are incorporated in the instrument or form part of the instrument as software solution.

Trade Measurement — Technical Policy

Policy number: TS - 024
Effective date: May 2016
Version date: December 2019
Version number: 2
Policy name: When an auxiliary (peripheral) device is fitted to a weighing instrument
Reviewed by: Davis White, Legal Metrology Advisor and Senior Trading Standards Officer
Approved by: Phil Sorrell, Team Leader Compliance and Inspection