IEC 63045:2020 pdf download – Ultrasonics – Non-focusing short pressure pulse sources including ballistic pressure pulse sources – Characteristics of fields.
5 Conditions of measurement 5.1 General Measurements shall be performed in a situation approximating conditions of actual operation. Parameters which shall be considered and documented include: – pressure pulse generator drive level range and level(s) for the measurements; – rate of pressure pulse release; – ambient temperature. 5.2 Measurements in the water test chamber In the water test chamber, the following conditions shall be considered and documented: – electrical conductivity of water in a measuring tank; – temperature of water in a measuring tank; – dissolved oxygen content of water in a measuring tank. Degassed water (see IEC TR 62781 for recommendations) at a specified nominal room temperature should be used in the measuring tank (test chamber) which shall be large enough to allow the measurement environment to approximate free-field conditions. Great care shall be taken to ensure that bubbles do not collect on the hydrophone nor anywhere in the beam path. The conductivity of the water shall be suitable for the hydrophone being used. The calibration data of the hydrophone shall be known at the temperature of the water in the measuring tank and at appropriate frequencies. NOTE Depending on the rarefactional amplitude p r of the pressure pulses, ultrapure water can be advisable to reduce the occurrence of cavitation nuclei.
5.3 Measurements in the dry test bench In the dry test bench, the following parameters shall be considered and documented: – material and thickness of a tissue mimicking pad; – coupling conditions between source aperture and tissue mimicking pad (e.g. dry, wet, silicone oil, ultrasound coupling gel, grease); – coupling force of the pressure probe or hydrophone to a tissue mimicking pad; – coupling force of the source aperture to a tissue mimicking pad. 6 Test equipment 6.1 Water test chamber The test chamber shall be a water tank constructed in a form that can be securely fixed to the pressure pulse generator so that the acoustic output from the pressure pulse generator is coupled into a volume of water. The chamber shall be sufficiently large to allow the expected position of any measurement point to be several centimetres away from any reflective boundary, in particular the water surface. The distance between all measurement points and reflective boundaries shall be chosen such that no spurious or multiple reflections of the pressure pulse interfere with the measurements.
There shall be a suitable mechanical holder for the hydrophone which is mounted on a coordinate positioning system to allow adjustment and measurement of the position of the hydrophone in three orthogonal directions relative to the measurement centre point. One axis (usually the z axis) of the coordinate positioning system shall be collinear with the beam axis. The relative position of the hydrophone shall be measurable with a precision of 0,5 mm or better. Care shall be taken to ensure that coupling membrane(s) between the source aperture and the water do not influence the measurements. Coupling media, for example ultrasound coupling gel, shall be applied as specified by the manufacturer if the source aperture is not directly submerged in the water. 6.1.1 Coordinate system All measurement coordinates and distances shall be given relative to the centre of mass of the source aperture, which defines the measurement centre point. All coordinates (x,y,z) shall be documented relative to the measurement centre point. The coordinates of the target location(s) shall be given relative to the measurement centre point.
6.1.3 Hydrophone for pressure pulse measurements Examples for appropriate hydrophones for pressure pulse measurements are listed in Table C.1 . For quality assurance, consistency checks may be required for periodic measurements of the pressure pulse source in order to assure that the device remains inside the specifications. These consistency checks can be required at regular intervals, for example each year, and additionally after servicing and repair. The hydrophone for quality assurance purposes shall have a robust construction and shall have a frequency response which does not vary by more than ±3 dB per octave over the frequency range from 0,5 MHz to 5 MHz. The effective diameter of the hydrophone should be as small as possible, it shall not exceed the source aperture and its value shall be stated.