Bruel & Kjaer 4440
An instrument that allows transducers to be calibrated accurately even in the presence of reflections, the 4440 cuts out the echoes caused by the boundaries of the enclosure so that free-field conditions are artificially achieved. The input continuous sine signal is gated to obtain a driving tone burst. The detector is gated and delayed to match the distance between the transmitter and the receiver, and the peak level is detected. The gate width (pulse length), tone-burst repetition frequency, and delay between the output signal and the measuring gate can all be adjusted to suit individual requirements. Apart from transducer calibrations, many other applications are possible: for example, generation of accurately timed pulses and transients for echo investigations, absorption measurements, and medical and biological research measurements. Gating System
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Bruel & Kjaer 4440
