The Measuring Instruments (Taximeters) Regulations 2006

Allowable Errors

3.—(1) Under rated operating conditions and in the absence of a disturbance, the error of measurement shall not exceed the maximum permissible error (MPE) value as set out in paragraph 17.

(2) Unless stated otherwise, MPE is expressed as a bilateral value of the deviation from the true measurement value.

(3) Under rated operating conditions and in the presence of a disturbance, the performance requirement shall be as set out in paragraph 18.

(4) The manufacturer shall specify the climatic, mechanical and electromagnetic environments in which the taximeter is intended to be used, power supply and other influence quantities likely to affect its accuracy, taking account of the requirements in this Schedule.

(a) Climatic environments—

• The manufacturer shall specify the temperature range. The minimum temperature range is 80°C and shall be within the upper temperature limit of 70°C and the lower temperature limit of -40°C. The manufacturer shall indicate whether the taximeter is designed for condensing or non-condensing humidity as well as the intended location for the instrument, that is open or closed.

(b) Mechanical environments—

(i) M3: This class applies to taximeters used in locations where the level of vibration and shock is high and very high, such as instruments mounted directly on machines or conveyor belts.

(ii) The following influence quantities shall be considered in relation with mechanical environments, namely—

(aa) vibration;

(bb) mechanical shock.

(c) Electromagnetic environments—

(i) E3: This class applies to taximeters supplied by the battery of a vehicle. Such instruments shall comply with the requirements of instruments used in locations with electromagnetic disturbances corresponding to those likely to be found in industrial buildings and the following additional requirements—

(aa) voltage reductions caused by energising the starter-motor circuits of internal combustion engines;

(bb) load dump transients occurring in the event of a discharged battery being disconnected while the engine is running.

(ii) The following influence quantities shall be considered in relation with electromagnetic environments—

(aa) voltage interruptions;

(bb) short voltage reductions;

(cc) voltage transients on supply lines or signal lines, or both;

(dd) electrostatic discharges;

(ee) radio frequency electromagnetic fields;

(ff) conducted radio frequency electromagnetic fields on supply lines or signal lines, or both;

(gg) surges on supply lines or signal lines, or both.

(5) Other influence quantities to be considered, where appropriate, are—

(a) voltage variation;

(b) any other quantity likely to influence in a significant way the accuracy of the taximeter.

(6) When carrying out the tests as envisaged in these Regulations, the following paragraphs apply—

(a) The basic rules for testing and the determination of errors are—

(i) the essential requirements specified in sub-paragraphs (1) to (4) shall be verified for each relevant influence quantity. These essential requirements apply when each influence quantity is applied and its effect evaluated separately, all other influence quantities being kept relatively constant at their reference value; and

(ii) the metrological tests shall be carried out during or after the application of the influence quantity, whichever condition corresponds to the normal operational status of the taximeter when that influence quantity is likely to occur.

(b) In relation to ambient humidity—

(i) according to the climatic operating environment in which the taximeter is intended to be used either the damp heat-steady state (non-condensing) or damp heat cyclic (condensing) test may be appropriate; and

(ii) the damp heat cyclic test is appropriate where condensation is important or when penetration of vapour will be accelerated by the effect of breathing. In conditions where non-condensing humidity is a factor the damp-heat steady test is appropriate.