Division 4.2.2.2 Measuring equipmentF1

The test wheel position on the trailer or the tyre test vehicle shall be equipped with a rotational wheel velocity measuring system and with transducers to measure the braking force and vertical load at the test wheel.

General requirements for measurement system: The instrumentation system shall conform to the following overall requirements at ambient temperatures between 0 °C and 45 °C:

1. (i)

   overall system accuracy, force: ± 1,5 % of the full scale of the vertical load or braking force;

2. (ii)

   overall system accuracy, speed: ± 1,5 % of speed or ± 1,0 km/h, whichever is greater.

Vehicle speed: To measure vehicle speed, a fifth wheel or non-contact precision speed-measuring system should be used.

Braking forces: The braking force-measuring transducers shall measure longitudinal force generated at the tyre–road interface as a result of brake application within a range from 0 % to at least 125 % of the applied vertical load. The transducer design and location shall minimise inertial effects and vibration-induced mechanical resonance.

Vertical load: The vertical load-measuring transducer shall measure the vertical load at the test position during brake application. The transducer shall have the same specifications as described previously.

Signal conditioning and recording system: All signal conditioning and recording equipment shall provide linear output with necessary gain and data reading resolution to meet the specified previous requirements. In addition, the following requirements apply:

1. (i)

   The minimum frequency response shall be flat from 0 Hz to 50 Hz (100 Hz) within ± 1 % full scale.

2. (ii)

   The signal-to-noise ratio shall be at least 20/1.

3. (iii)

   The gain shall be sufficient to permit full-scale display for full-scale input signal level.

4. (iv)

   The input impedance shall be at least 10 times larger than the output impedance of the signal source.

5. (v)

   The equipment shall be insensitive to vibrations, acceleration, and changes in ambient temperature.