The Measuring Instruments (Cold-water Meters) Regulations 2006

Permissible Effect of Disturbances

16.—(1) Electromagnetic immunity—

(a) The effect of an electromagnetic disturbance on a cold-water meter shall be such that—

(i) the change in the measurement result is no greater than the critical change value as defined in paragraph (c);

(ii) the indication of the measurement result is such that it cannot be interpreted as a valid result, such as a momentary variation that cannot be interpreted, memorised or transmitted as a measuring result.

(b) After undergoing an electromagnetic disturbance the cold-water meter shall—

(i) recover to operate within MPE;

(ii) have all measurement functions safeguarded; and

(iii) allow recovery of all measurement data present just before the disturbance.

(c) The critical change value is the smaller of the two following values—

(i) the volume corresponding to half of the magnitude of the MPE in the upper zone on the measured volume;

(ii) the volume corresponding to the MPE on the volume corresponding to one minute at Q₃.

(2) Durability—

(a) After an appropriate test, taking into account the period of time estimated by the manufacturer, has been performed, the criteria in paragraphs (b) and (c) shall be satisfied.

(b) The variation of the measurement result after the durability test, when compared with the initial measurement result, shall not exceed—

(i) 3% of the metered volume between Q₁ included and Q₂ excluded;

(ii) 1.5% of the metered volume between Q₂ included and Q₄ included.

(c) The error of indication for the volume metered after the durability test shall not exceed—

(i) ± 6% of the metered volume between Q₁ included and Q₂ excluded;

(ii) ± 2.5% of the metered volume between Q₂ included and Q₄ included.