ISO 5348 pdf download.Mechanical vibration and shock — Mechanical mounting of accelerometers
1 Scope
This International Standard describes the mounting characteristics of accelerometers to be specified by the manufacturer and makes recommendations to the user for mounting accelerometers. Application of this International Standard is limited to the mounting of accelerometers which are mounted on the surface of the structure in motion, as illustrated in the simplified diagram shown in figure 1 . It is not applicable to other types of transducers, such as relative motion pick-ups.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 2041 :1 990, Vibration and shock — Vocabulary. ISO 2954:1 975, Mechanical vibration of rotating and reciprocating machinery — Requirements for instruments for measuring vibration severity.
ISO 5347-1 4:1 993, Methods for the calibration of vibration and shock pick-ups — Part 1 4: Resonance frequency testing of undamped accelerometers on a steel block. ISO 5347-22:1 997, Methods for the calibration of vibration and shock pick-ups — Part 22: Accelerometer resonance testing — General methods. ISO 8042:1 988, Shock and vibration measurements — Characteristics to be specified for seismic pick-ups.
3 Definitions
For the purposes of this International Standard, the terms and definitions given in ISO 2041 apply.
4 Characteristics to be specified by manufacturers of accelerometers
The manufacturer shall specify the following characteristics: a) mounting-surface characteristics pertinent to the mounting device(s) furnished with the accelerometer, e.g. surface finish roughness, surface flatness, hole perpendicularity and tap class; b) the geometrical dimensions of the accelerometer including — the position of the centre of gravity of the accelerometer as a whole, — the position of the centre of gravity of the seismic mass of the accelerometer; c) the mounting technique used during calibration; d) the recommended and maximum (i.e. for less than 2 % change in the useful frequency range) mounting torque; e) temperature limitations of the accelerometer and fastening device; f) pertinent mechanical characteristics, i.e. — total mass, — material of base, — the lowest unmounted resonance frequency of the accelerometer, — the frequency response characteristic under well-defined mounting conditions, describing the object on which the transducer is mounted in terms of mass, material and dimensions, — the maximum transverse sensitivity, and the frequency at which it was determined; g) a description of the various fastening devices provided for the accelerometer, i.e. — diameter, — thread, — material; h) the frequency response curves of the accelerometer with the type of mechanical mounting recommended by the manufacturer and the effect of special mounting devices supplied with the accelerome
5 Consideration in the selection of a mounting method
5.1 General considerations 5.1.1 Procedures An accelerometer will achieve optimal performance only if the following general procedures are followed: a) the accelerometer shall perform as nearly as possible the same motion as the structure under test at the accelerometer attachment; b) the motion of the structure shall be changed as little as possible by the addition of the accelerometer; c) the ratio of the signal from the accelerometer to the motion of the accelerometer shall not be distorted by operating too near to its mounted fundamental resonance frequency. 5.1.2 Conditions In order to achieve these ideal conditions, it is necessary to ensure that: a) the accelerometer and its mounting are as rigid and firm as possible (the mounting surfaces shall be as clean and flat as possible); b) the mounting introduces minimum distorting motions of its own (for example, simple symmetrical mountings are best); c) the mass of the accelerometer and mounting are small in comparison with that of the dynamic mass of the structure under test (see ISO 2954). 5.2 Specific considerations 5.2.1 Frequency range of operation The accelerometer shall be used well below its fundamental resonance frequency. If it is possible to use the manufacturers’ recommended mounting, then operation at frequencies not greater than 20 % of their quoted mounted resonance should, in the case of undamped accelerometers (resonance magnification factor Q greater than 30 dB), ensure in most cases that errors of only a few percent on the amplitude response occur. If an estimate of the approximate error is required, it may be made on the basis of an equivalent linear spring-mass system with a given value of damping. NOTE — For single shock measurements, one may expect errors of only a few percent if the mounted fundamental resonance frequency is ten times greater than the inverse of the pulse duration.