The Weighing Equipment (Non-automatic Weighing Machines) Regulations 1988

10.  Comparison testing

(a) Machines having a weighing mode in which it is possible to obtain more than one determination of any test load by means of more than one tare, weight indicating or printing devices shall, for each such weighing mode, be tested as described in subparagraphs (b) and (c) below.

(b) Testing shall be carried out for at least three different values of test load.

(c) The inspector shall compare each reading with all the other readings of the same test load, the other readings being obtained from different weight indicating, printing and tare devices. The difference between any two of these readings must not exceed—

(i) zero, where the two readings are obtained from two digital devices having the same scale interval;

(ii) the larger of the scale intervals, where the two readings are obtained from digital devices having different scale intervals;

(iii) the smaller of the absolute values of the appropriate prescribed limits of error where the two readings are obtained from two analogue devices; or

(iv) either the absolute value of the appropriate prescribed limits of error of the analogue device or the scale interval of the digital device whichever is the greater, where one of the two readings is obtained from an analogue device and the other is obtained from a digital device.