Document ID: chunk:federal_register_of_legislation:F2005L03990:front:0:p27
Version: federal_register_of_legislation:F2005L03990
Segment Type: other
Provision Reference: 
Character Range: 67104–69735

possible. Any mounting having a lowest resonance frequency equal to at least 5 times the frequency FH of the data channel considered shall be considered valid. Acceleration transducers in particular should be mounted in such a way that the initial angle of the real measurement axis to the corresponding axis of the reference axis system is not greater than 5° unless an analytical or experimental assessment of the effect of the mounting on the collected data is made. When multi-axial accelerations at a point are to be measured, each acceleration transducer axis should pass within 10 mm of that point, and the centre of seismic mass of each accelerometer should be within 30 mm of that point.
4. RECORDING
4.1. Analogue magnetic recorder
 Tape speed should be stable to within not more than 0.5 per cent of the tape speed used. The signal-to-noise ratio of the recorder should not be less than 42 dB at the maximum tape speed. The total harmonic distortion should be less than 3 per cent and the linearity error should be less than 1 per cent of the measurement range.
4.2. Digital magnetic recorder
 Tape speed should be stable to within not more than 10 per cent of the tape speed used.
4.3. Paper tape recorder
 In case of direct data recording the paper speed in mm/s should be at least 1.5 times the number expressing FH in Hz. In other cases the paper speed should be such that equivalent resolution is obtained.
5. DATA PROCESSING
5.1. Filtering
 Filtering corresponding to the frequencies of the data channel class may be carried out during either recording or processing of data. However, before recording, analogical filtering at a higher level than CFC should be effected in order to use at least 50 per cent of the dynamic range of the recorder and to reduce the risk of high frequencies saturating the recorder or causing aliasing errors in the digitilising process.
5.2. Digitilising
5.2.1. Sampling frequency
 The sampling frequency should be equal to at least 8 FH. In the case of analogical recording, when the recording and reading speeds are different, the sampling frequency can be divided by the speed ratio.
5.2.2. Amplitude resolution
 The size of digital words should be at least 7 bits and a parity bit.
6. PRESENTATION OF RESULTS
 The results should be presented on A4 size paper (ISO/R 216). Results presented as diagrams should have axes scaled with a measurement unit corresponding to a suitable multiple of the chosen unit (for example, 1, 2, 5, 10, 20 millimetres). SI units shall be used, except for vehicle velocity, where km/h may be used, and for accelerations due to impact where g, with g =