Sound and Vibration Instrument Hire and Calibration
Bruel & Kjaer UA 0559 Accelerometer Filter
B&K UA 0559 : Mechanical Filter for Accelerometers
£ 2 a day *
Vibration measurements where instrumentation is not equipped with low-pass filters
Measurement of low frequency, low level vibration often masked by high frequency, high acceleration levels.
Protection of accelerometer and preamplifier from high level shocks
Reduction of sensitivity to transverse vibrations
Prevents the accelerometer from detecting high frequency vibration
Prevents the excitation of accelerometer resonance
Usable with all types of piezoelectric accelerometers
Cut-off frequency selected by adjusting the load mass
Breaks ground-loop paths
Mechanical Filter UA 0559 is placed between an accelerometer and the mounting point on the test object in order to prevent the accelerometer from detecting high frequency vibration. There are several instances where this may be desirable:
To measure low frequency vibration, possibly at low levels, and where high level, high frequency acceleration masks the low frequency components because of preamplifier overload, distortion, lack of electronic filters etc.
Where the accelerometer resonance frequency is being excited by high frequency vibration of possibly insignificant level, causing wide band measuring errors and overload. Thus by using the mechanical filter the useful dynamic range of measuring instruments is increased by more than 20 dB.
Where it is feared that the accelerometer could be subjected to transient shock levels beyond its maximum capability, thus preventing damage.
Where the measuring instrumentation has a high frequency response in excess of that required and is not equipped with suitable low-pass filters. Vibration measurement with a wide-band sound level meter is a notable example of this case.
Where it is wished to obtain a specific cut-off frequency without the use of specially built electronic filters or elaborate tunable filters. For example, when measuring vibration as applied to the human hand, arm or body, the measuring range is normally limited to below 1000 Hz.
The filter consists of an upper and lower part of stainless steel bonded together and electrically separated by a specially formulated butyl rubber core. The two halves are equipped with standard accelerometer threads (10 - 32UNF), male and female respectively. A tommy bar can be inserted transversely through the two halves to relieve the rubber core of excessive twisting torque when the accelerometer is tightened down. Where the butyl rubber core can be contaminated with hydrocarbon substances such as oil or fuel, a resistant silicone rubber sealer should be used (e.g. Dow Corning Type 733 RTV).