Transducer Selection Criteria—European Standards
For transducers manufactured to European standards, technical and performance information is provided throughout this catalog
based on the definitions below. A comprehensive data sheet is supplied with most flaw detection transducers at no charge.
Description Explanation
Element size D or a x b Diameter D or length x width a x b of the transducer element. The size of the element strongly affects the shape of the
transmitted sound field. Slight deviations, (e.g., imperfect shape or positions with reduced radiation due to poor bonding)
cause considerable evaluation errors, even when calibrated to a reference flaw.
Nominal frequency f The mean frequency of all probes of the same type. The frequency has a great influence on the evaluation of reflectors.
Even the shape of the sound field and the reflection behaviour of angled reflectors are strongly dependent on the
frequency. With increasing frequency, the echo height from non-vertically positioned reflectors to the sound beam
decreases. This is why each probe is checked by our Quality Control to see if its frequency coincides with the nominal
frequency, according to the identification label, within very narrow tolerances. This is entered into the probe data sheet.
Bandwidth B The range of frequencies in the echo pulse whose amplitude, at the most, is 6 dB less than the maximum amplitude.
fo - fu
B = ------------ X 100%
f
fo = upper, fu = lower frequency limit for a 6 dB drop in amplitude.
With B = 100%, a 4 MHz, probe for example, has an fo of 6 MHz and an fu of 2 MHz. Large bandwidths mean shorter echo
pulses, which mean high resolution and a good penetration power, because the lower frequencies of the pulse become less
attenuated than the nominal frequency. At high attenuation, the frequency of reflected signals decreases, compared to the
nominal frequency, as the distance increases. This must be taken into account with flaw evaluation. The bandwidth of each
probe is therefore checked and must, within narrow tolerances, coincide with the mean value of all probes.
Focal distance F
Near field length N
The distance of a small reflector from the probe producing the highest possible echo. Probes are focused in order to detect
small reflectors and produce a high echo amplitude. Focusing is only possible within the near field of the probe.
The near field length N is the focal distance of the unfocused probe which constitutes the sound pressure maximum at the
largest distance from the probe. N is determined by D, c and f.
D2
eff D2
eff . f
For D >> λ is: N = --------- = -------------
4 λ 4 c
λ = wave length c = sound velocity Deff = effective element diameter
Focal point and near field length are the distances with the best sound concentration and reflector recognition. Therefore,
when a probe is selected for a critical test, the flaw expectancy range must be in the focal area or near field length. The
data in the tables refers to steel with the exception of immersion testing in water.
Focal diameter FD6 Diameter of the sound field in the focal distance or near field length with a 6 dB drop of the echo indication.
F . c 1 F
For D >> λ is: FD 6 = ------ = ---- k . D eff with k = -----
f - Deff 4 N
Pulse shape The presentation of signals, as they are at the instrument input coming from plane reflectors.
Spectrum Display of all the frequencies in the echo pulse. The frequency amplitudes are shown over the frequency.
Beam angle ß The angle between the main beam and the normal axis of the test surface.
Transducer Selection Criteria—European StandardsFor transducers manufactured to European standards, technical and performance information is provided throughout this catalogbased on the definitions below. A comprehensive data sheet is supplied with most flaw detection transducers at no charge.Description ExplanationElement size D or a x b Diameter D or length x width a x b of the transducer element. The size of the element strongly affects the shape of thetransmitted sound field. Slight deviations, (e.g., imperfect shape or positions with reduced radiation due to poor bonding)cause considerable evaluation errors, even when calibrated to a reference flaw.Nominal frequency f The mean frequency of all probes of the same type. The frequency has a great influence on the evaluation of reflectors.Even the shape of the sound field and the reflection behaviour of angled reflectors are strongly dependent on thefrequency. With increasing frequency, the echo height from non-vertically positioned reflectors to the sound beamdecreases. This is why each probe is checked by our Quality Control to see if its frequency coincides with the nominalfrequency, according to the identification label, within very narrow tolerances. This is entered into the probe data sheet.Bandwidth B The range of frequencies in the echo pulse whose amplitude, at the most, is 6 dB less than the maximum amplitude.fo - fuB =-X 100%fโฟ =บน ฟู =ขีดจำกัดความถี่ต่ำสำหรับวาง 6 dB ในคลื่นมี B =โพรบ 100%, 4 MHz ตัวอย่าง มีสมนา 6 MHz และฟูของ 2 MHz แบนด์วิธขนาดใหญ่หมายถึง สั้นสะท้อนกะพริบ ซึ่งหมายความว่า กำลังเจาะดี และความละเอียดสูงเนื่องจากเป็นความถี่ต่ำของชีพจร น้อยกว่าไฟฟ้าเคร...กว่าความถี่ที่ระบุ ที่มีความยาวสูง ความถี่ของสัญญาณสะท้อนลดลง เมื่อเทียบกับการระบุความถี่ ระยะทางที่เพิ่มขึ้น นี้ต้องนำมาพิจารณาด้วยการประเมินปัญหา แบนด์วิธของแต่ละโพรบจึงมีการตรวจสอบ และต้อง ภายในยอมรับแคบ สอดคล้องกับค่าเฉลี่ยของคลิปปากตะเข้ทั้งหมดโฟกัสระยะ Fใกล้เขตข้อมูลความยาว Nระยะหรือขนาดเล็กจากโพรบการผลิตสะท้อนได้สูงสุด คลิปปากตะเข้จะเน้นการตรวจสอบreflectors ที่ reflectors ขนาดเล็กและผลิตคลื่นสะท้อนสูง เน้นได้ภายในเขตใกล้ของโพรบความยาวฟิลด์ใกล้ N คือ ระยะโฟกัสของโพรบ unfocused ซึ่งเสียงความดันสูงสุดในการหองโพรบใหญ่ที่สุด N จะถูกกำหนด โดย D, c และ fD2eff D2eff fสำหรับ D >> λคือ: N =--- =--4 λ 4 cΛ = c ความยาวคลื่น =ความเร็วเสียง =เส้นผ่าศูนย์กลางขององค์ประกอบที่มีประสิทธิภาพแน่นอนโฟกัสจุด และใกล้ความยาวของฟิลด์จะมีระยะห่างสุดเสียงเข้มข้นและหรือการรู้จำ ดังนั้นเมื่อโพรบถูกเลือกสำหรับการทดสอบสำคัญ ช่วงเดาปัญหาต้องอยู่ ในพื้นที่โฟกัส หรือ ใกล้ความยาวของฟิลด์ ที่data in the tables refers to steel with the exception of immersion testing in water.Focal diameter FD6 Diameter of the sound field in the focal distance or near field length with a 6 dB drop of the echo indication.F . c 1 FFor D >> λ is: FD 6 = ------ = ---- k . D eff with k = -----f - Deff 4 NPulse shape The presentation of signals, as they are at the instrument input coming from plane reflectors.Spectrum Display of all the frequencies in the echo pulse. The frequency amplitudes are shown over the frequency.Beam angle ß The angle between the main beam and the normal axis of the test surface.
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