Dynamic calibration of the pressure transducers and accelerometers are carried out by applying dynamic mechanical inputs to them. Determination of those transducers' sensitivities, defined as the ratio of electrical output of the transducer to the mechanical input, is an important task for calibration laboratories. Data obtained during calibration are processed in order to have the peak values of the input and output signals which are sampled by data acquisition boards. Different approximations are made such as fitting the data in the range of 90% of the maximum value for parabola or half-sine waveform. It is clear that waveform model used and also the resolution and the sampling rate of the data acquisition boards have effects on the accuracy of the sensitivity of the transducer. For the investigation, the electrical output signal of the transducer corresponding to the mechanical input is recorded and simulated with different resolutions and sampling rates. Those data are processed for the waveforms of half-sine, parabola, Gaussian distribution. The effect of the waveform model of the input quantities on the dynamic sensitivity is discussed in this paper.
Sonobuoy is a sensory device collecting underwater acoustic signals and transmitting them to some base stations via RF waveforms. In this paper, newly developed Turkish sonobuoy project's sea performance is presented. The proposed system architecture has been developed as a prototype in the lab environment. Lab experiments have been conducted successfully over a test bench representing typical submarine detection case. These experiments are designed to calibrate sensory system and optimize the RF transmission. The sonobuoy system has been used in open sea environment for the similar submarine scenario. The bearing angle representing submarine position has been detected within ± 10 o accuracy as required. We, then, compared the lab and experimental open sea results that were identical.
Laser pistonphone for absolute microphone calibration in low frequency range has been realized at UME. According to the operation principle of pistonphone, the motion of a piston, which is driven electro-mechanically in a closed acoustical coupler, produces a sound pressure. Accurate measurements of the piston displacement by laser interferometry enable accurate determination of the sound pressure and, as a result, the pressure sensitivity of the microphone exposed to the sound pressure inside the coupler. Homodyne Michelson interferometer with He-Ne laser was used for displacement measurements. Since the pistonphone is operating at low frequencies, the fringe-counting method was used for the signal processing. Calibrations of LS1P microphones with the uncertainty less that 0. 15 dB have been performed using laser pistonphone. Other possible metrological applications of laser pistonphone are also described in the paper.
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