| 摘要 |
An apparatus for making pulsed acoustic measurements to determine particle size in a sample ( 1 ) such as a colloid. The apparatus includes two electrodes ( 2 ) between which an electric voltage is applied to the sample. The voltage is applied in short pulses. The applied voltage generates an acoustic signal, such as a sound wave ( 5 ), in the sample which is detected with a transducer ( 3 ) after the wave ( 5 ) has passed through a delay element ( 4 ). The delay element ( 4 ) is used to introduce enough of a time delay between the application of the voltage pulse and sound wave ( 5 ) reaching the transducer so that the received wave's signal can be isolated from any signal generated in the transducer ( 3 ) by the applied voltage. The delay element ( 4 ) and the transducer ( 3 ) are arranged into a geometry, or, alternatively, the delay element ( 4 ) is shaped, so that any reflections of the sound wave ( 5 ) from the sidewalls of the delay element ( 4 ) are deflected away from the transducer ( 3 ). This reduces interference, particularly at low frequencies.
|
