Testing of point-of-sale systems _POS_ as components of non

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					   Testing of point-of-sale systems (POS) as components of non-automatic
            weighing instruments (NAWI) acceptable for verification
                           Unofficial German translation,
                             summary and explanation
                      of WELMEC Guide 2.2 (Issue 2), 1997:

       "Guide for Testing Point-of-Sale Devices (Non-automatic Weighing

Published by Working Group 1.12 "Weighing instruments"
For questions please contact: Mr. Werner Baars
Tel.: +49 531 – 592 1145
Fax: +49 531 – 592 1105


  1 Preliminary remark
  2 General information
  3 Scope
  4 Test specimen
  5 Written declaration of the manufacturer
  6 Documentation
  7 Technical requirements
  8 Metrological tests
  9 Software

1 Preliminary remark

This guide is an unofficial translation, summary and explanation of WELMEC
Document 2.2 (2nd edition, 1997). It should be used only together with the original
English version which is more frequently referred to and which is the binding version.
The original version is available under
2 General information

According to WELMEC 2.2, there are generally two possibilities of approving a POS
as a per, subject to legal control, of a non-automatic weighing instrument (NAWI):

A.     The type of the POS is included in the EC type-approval certificate or in a
       supplement to the EC type-approval certificate for a specific NAWI for direct
       sales to the public under point 4.2.1 (Peripheral devices for applications subject
       to legal control).

B.     A test certificate is issued for the POS which allows connection of the POS to
       any suitable NAWI acceptable for verification.

       A weighing instrument is suitable for connection of a POS if it is a weighing
       instrument for direct sales to the public and if the EC type-approval certificate
       for the weighing instrument contains the general clause for peripheral devices
       subject to legal control as well as a section on the connection of point-of-sale
       devices according to WELMEC 2.2, Annex 5.

In both cases, the POS is tested in accordance with WELMEC 2.2, although this
Guide is intended to create uniform conditions and bases for the more flexible
solution (b) which is basically to be preferred to solution (a).

3      Scope

The following two POS variants are covered by WELMEC Guide 2.2:

    Price-computing POS which only receive weight data from the NAWI.

    Non-price-computing POS which receive all main indications (weight, unit price,
     price to pay, possibly tare values) from the price-computing weighing instrument.

    Non-price-computing POS which transfer PLU values (e.g. unit price) to the price-
     computing weighing instrument and then receive all main indications (see above)
     from it.

    Fix-programmed POS and free-programmable PC-based POS
   POS which transfer the tare input values and, where appropriate, a zero-setting
    instruction to the weighing instrument.

WELMEC Guide 2.2 is not applicable to:

   POS with a zero setting, tare weighing or tare-compensating device of their own.

   Simple fix-programmed printers which, for example, just repeat the weighing
    results and other main indications.

   POS whose display replaces the display of the weighing instrument so that the
    display of the point-of-sale device alone furnishes all main indications; such
    POS's are considered to be indicators and are intended to be tested according to
    WELMEC Guide 2.1 (Guide for Testing Indicators).

4   Test specimen

Performance of the technical and metrological tests according to sections 5 and 6
requires a test specimen of the POS which is connected to a suitable NAWI for direct
sales to the public via a protective interface; for the weighing instrument, an EC type-
approval certificate must have been issued or the weighing instrument must just be
subjected to an EC type-approval examination.

The POS must be equipped with all proposed interfaces. For disturbance tests
according to section 6, a peripheral device (e.g. a printer) or at least an open-end
cable must be connected to each interface. If there are several interfaces of the same
type (e.g. RS 232). only one interface of this type needs to be tested.

The manufacturer of the POS or the applicant specifies at least one suitable weighing
instrument which will also be made available for the tests and demonstrates its
suitability by the EC type-approval certificate.

5   Written declaration of the manufacturer

The manufacturer of the POS must make the following written declaration (the data in
brackets refer to EN 45501):
   Name and address of manufacturer and his authorized representative, if
   A declaration stating that the POS, type..., including its implemented software,
    meets the requirements of standard EN 45501, with the following permissible
    exceptions, if applicable:

   Different digit heights for customer and seller display (4.14.6)

   Digit height on the seller side  9.5 mm, but clearly visible (4.14.6)

   Unit price or price to pay are displayed by the POS; although these indications are
    visible for more than 3 s, they are visible only until the next item is entered
    (4.15.3., section 5).

   The POS cannot be disturbed or inadmissibly influenced via its interfaces (5.3.6).

6   Documentation

Upon application, the applicant must submit the information and documents required
in sections 4.1 to 4.5 together with the written declaration of the manufacturer
according to section 3. Drawings, product descriptions and other documents must be
clearly identifiable by a designation or number and bear their creation data as well as
the date of the last revision.

A: General description and explanations regarding the function of the POS (data in
    brackets refer to EN 45501)

    1 Intended use, general description of the POS, e.g.
        functions subject to legal control and not subject to legal control
        important sub-assemblies
        price computing yes/no
        tare input device yes/no
        free-programmable yes/no

    2 Descriptive information (7.1), in particular:
        manufacturer
        type designation, variants (hardware and software)
       voltage supply
       kind of display (e.g. dot matrix or monitor)

B. List and description of all important components and devices of the POS
   1 Software description (see section 7 "Software")
   2 Measures for securing of components and pre-set controls (4.1.2)
   3 Multiple use of indicating devices (4.4.4)
   4 Printing devices (4.4.5), printing of weighing results (4.6.11, 4.7.3) and other
      main indications (4.15.4, 4.17)
   5 Storage device (4.4.6)
   6 Other functions of price-computing POS (4.15)
       Special applications (4.15.4)
       Self-service instruments (4.15.5)
   7 Interfaces
       Complete list of all interfaces provided
       Intended use (peripheral devices)
       Declaration regarding non-reactiveness (5.3.6), see section 3
       Complete list of all data and functions which may be interchanged or
        released via the POS-NAWI interface; declaration of completeness of this list
       Special connecting cables, if applicable

   8 Other devices and functions not subject to legal control

C. Special information

   1 Special operating conditions (3.9.5)
   2 Reaction to significant faults (5.1.1, 5.2, 4.14.9)
   3 Check of the indication upon switch-on (5.3.1) (for segmented displays only,
      not for monitors)
   4 Other special information

D. Drawings, circuit diagrams, markings
   1 Block diagrams, technical description of the design
   2 Schematic drawings, circuit diagrams
    3 Description of the keyboard and indication of keyboard assignment
    4 Drawing of data plate with the data required (7.1)
    5 Examples of all possible printouts
    6 View of the POS (drawing or photo), including indication of the spaces for
       verification mark and protective marks (also green M)

E. Specification of the weighing instrument with which the POS is to be tested;
    possibly proof of suitability by EC type-approval certificate for the weighing
    instrument (see section 2, "Test specimen").

7   Technical requirements

On the basis of the test specimen and a check list (see WELMEC 2.2, Annex 2) it is
checked whether the type of the POS meets the technical requirements of EN 45501
(see WELMEC 2.2, section 5).

The following deviations from EN 45501 are permitted provided the essential
requirements of Directive 90/384/ECC are otherwise met (see also para. 3):

   The digit heights of customer and seller display are different (EN 45501, 4.14.6,
    paras. 1 and 2)

   The digit height on the seller side is not  9.5 mm, but clearly visible (4.14.6, para.

   Unit price and/or price to pay are displayed (by the POS) for more than 3 s, but
    only until the next item is entered (4.15.3, para. 5)

   The display need not be checked if the display of the POS is not a segmented
    display but a monitor (5.3.1)

   The point-of-sale display need not repeat all main indications (weight, unit price,
    price) if these are displayed by the weighing instrument and are clearly visible to
    buyer and seller.

If and where appropriate, these deviations are to be mentioned in the test certificate
together with an explanation of how the requirements of Directive 90/384/EEC can
nevertheless be met. For free-programmable POSs, the software requirements
according to WELMEC Guide 2.3 (see section 7 "Software") are valid in addition.
8   Metrological tests

The following tests (see WELMEC Guide 2.2, section 6) are to be performed with the
complete test specimen (NAWI + POS + additional peripheral devices on the POS):

Voltage variations (A.5.4)
    During the test, repeated printouts are to be performed with the POS; the
    printouts must be identical with the indication of the weighing instrument.
Electrical disturbance tests (B.3.1-B.3.4)
    During the tests, repeated printouts are to be performed with the POS (for
    example with a special test program). A deviation between the printed value and
    the value displayed on the weighing instrument is considered to be a significant
    fault. Error messages or no printout during the electrical disturbance are not
    regarded as significant faults.

9   Software

As a matter of principle, the software requirements of WELMEC Guide 2.3 "Guide for
Examining Software (Non-automatic Weighing Instruments), 1995, are valid for both,
fix-programmed and free-programmable POSs.

For fix-programmed POSs it is, however, assumed that software requirement 1
(protection against manipulation) is basically met by protective interfaces,
requirement 2 (software separation by a software interface) is not relevant and
requirement 4 (software documentation) is also met when the descriptions and
explanations mentioned under 4 are available. Only requirement 3 (software
identification) remains, i.e. the POS must at least be in a position to display the
current version number of the software (firmware) to allow, for example, the reference
software identification stated in the test certificate to be compared upon verification.

For free-programmable PC-based point-of-sale devices, a description of the
function of the complete point-of-sale software containing at least the following
descriptions and explanations must be submitted for the software test according to

   Required hardware and software environment
   Block diagram(s) and/or schematic description of the design and interaction of
    software modules subject and not subject to legal control

   Description of the software module subject to legal control and of the software
    interface(s) for modules not subject to legal control

   List of all parameters subject to legal control (e.g. all main indications such as
    weight, unit price, price to pay, tare values, symbols, units) and functions (e.g.
    tare input, zero setting of the weighing instrument, price computation, price

   Brief description of the parameters and functions

   Description of the complete sets of instructions to be interchanged via the
    protective hardware interfaces to the weighing instrument or to peripheral devices
    subject to legal control (e.g. printers).

   Written declaration on the completeness of this/these list(s)

   Description of the measures taken for software security (e.g. checksum, control
    devices, "footprint") and software identification (e.g. display of a check number,
    checksum or version number)

   Instructions for checking the software identification upon verification

   Written declaration that the POS, including its implemented software, is in
    compliance with standard EN 45501:1993 (see section 3).

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