IEC TS 62903 pdf free download
IEC TS 62903 pdf free download.Ultrasonics – Measurements of electroacoustical parameters and acoustic output power of spherically curved transducers using the self-reciprocity method.
6 Requirements of the measurement system
6.1 Apparatus configuration
The electrical system of the apparatus consists of a tone burst generator, a current monitor (probe), an oscilloscope and two switches. The acoustical system consists of a water tank for the measurements, a measurement hydrophone, fixtures, positioning and orientation systems (for both the transducer and the hydrophone), displacement sensors or indicators, and a stainless-steel reflector, as shown in Annex F. The apparatus for determining the effective radius and the self-reciprocity calibration are shown in Figures F.1 and F.2, respectively.
6.2 Measurement water tank
The tank shall have sufficient effective space of water bath to ensure that the maximum distance between the hydrophone and the transducer can be achieved to meet the requirements for fixtures, positioning and orienting the devices. The minimum dimensions of the tank for the tone burst field measurement only should be (R + cr) X (2Rcr + c2r2)1’2 x (2Rcr + c2r2)1’2 (length x width x height), where R is the radius of curvature, c is the speed of sound in water, r is the pulse duration and less than or equal to 30 cycles. Considering other requirements the tank should be not smaller than
0,55 m x 0,32 m x 0,38 m (length x width x height). The tank is filled with degassed water, and the water temperature is indicated by a thermometer.
6.3 Fixturing, positioning and orientation systems
The transducer and the hydrophone shall be fixed on fixtures that allow positional adjustment of the devices in three perpendicular directions as well as allowing their angles of azimuth and elevation to be independently and continuously being adjusted. The positioning accuracy should be better than ±0,1 mm in the axial direction z and ±0,01 mm in the lateral directions x and y, while the orientation accuracy should be better than ±0,05°. The resolution of the displacement sensor should be 0,01 mm or less.
6.4 Reflector
The reflector is a thick plate or cylinder made of stainless steel. One of the planes or terminal surfaces of the reflector is used as a reflection plane that should be flat to ±10 pm and should also show a surface finish good to ±5 pm. The thickness of the reflector shall be large enough to ensure that the first echo from the rear surface does not interfere with that from the front surface at the lowest frequency used. The reflector diameter shall be sufficient to reflect the entirety of the ultrasonic beam energy. The reflector diameter should be at least twice the
—26 dB beam width or greater than the aperture of transducer whichever is the greater. The average amplitude reflection coefficient rav(fl) is almost a constant 0,973 at the interface between water and stainless steel when the focus half-angle ft is less than 13°. For other 11 values, rav(fl) can be picked up from the data of Table A.2 in Annex A.
6.5 Current monitor (probe)
The frequency response of the current sensitivity of the monitor should be constant up to 1,4 times of the frequency of the current to be measured. The maximum detectable current should be greater than 1,5 times of the current to be measured. The rise time should be shorter than or equal to 20 ns. The accuracy should be better than or equal to ±1 %.IEC TS 62903 pdf download.
