Weighbridges - weighing memorandum for special applications


The National Weights and Measures Laboratory (NWML) is a section within the Department of Trade + Industry.

NWML has instructed officers in the field to ensure that remote weighing sites are properly protected from an electrical supply point of view.

In cases where remote weighbridges and similar equipment is operated from small generator supplies there is a mandatory requirement to fit power protection devices in series with the electrical supply.

Memorandum WM 429

The NWML has issued a Memorandum describing both the equipment which must be protected and how. The main part of of the Memorandum is transcribed here: An original is available on request from your local Weights + Measures.

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Department of Trade and Industry (November 1988)

Stanton Avenue Teddington Middlesex TW11 0JZ

Memorandum for the guidance of Inspectors of Weights and Measures


Section 12

The Secretary of State has issued the following amendments to the respective Notices of Examination/Certificates of Approval.

Generator powered equipment amendment No. 1 dated 14 October 1988

Type of Machine

Code Index

Counter machines

V (2) d V (2) e

Platform machines

V (6) d


V(6) d

Person weighing machines

V (6) f

Overhead weighing machines

V (7)

Milk weighing machines

V (8)

Suspended weighing machines

V (9) a

Crane weighing machines

V (9) b

Issued by NWML

Digital electronic machines and associated approved peripheral equipment.

As described in the Notice or minor modification to the Notice of Certificate or authorised variant thereof but having where appropriate the supply from a local generator in place of the mains supply.

In which case there shall be between the generator and the weighing equipment a constant voltage transformer Advance GT series of between 100 VA and 1000 VA rating. The rating chosen must be such that the minimum load on the CVT is not less than 5% of the rated output of the CVT and the maximum load including transient loads such as printing does not exceed the rating of the CVT.

The output of the CVT must be dedicated to the weighing systems and either:-

(i) hard wired directly to the system or

(ii) via a non standard connector in which case the output shall be marked 'for weighing system only'.

end of memorandum