Forum Technical Discussions      Re: calibration Posted by: Nigel Armstrong (PID_728), E-mail: Address, on November 20, 2008 at 06:23 : In Reply to: Re: calibration posted by : LANRE ALAPINI , E-mail: Address, on November 20, 2008 at 06:21 : Lanre, if your equipment is fitted with a single or twin option ensure that you are in the correct mode. With BOTH single and twin I would position the 1st backwall echo at zero on the timebase and the second and 3rd at 5 and 10 and then delay off so that the 1st BWE is on 5 and the 2nd on 10 (illustrative figures for compression wave only). That takes care of any delay line/perspex wedge sound path. Tom Nelligan wrote some technical differences, i wrote that the concept of calibration is identical for both single and twin - traceability, accuracy, repeatability. Enlighten me please Lanre, what has happened or been said that makes you concerned there may be a difference? ----------- Start Original Message ----------- : nigel, if i get you right, all things being equal theres no different between calibrating with dual element transducer and single element transducer : : Lanre : : Aside form the technical differences which Tom has outlined, the philosophy of calibration must be the same no matter which tools you are using - namely, traceability, accuracy and repeatability. Before commencing calibration ensure you are familiar with all your equipment's characterisitics (read manufacturer's literature/operating manuals/technical references) and that it is undamaged and in good working order. Both the thickness meter or flaw detector, depending on which you are using) and the calibration block should bear valid calibration certificates and have passed the most recent proceduralised in-house checks as evidenced by a log record. The calibration block MUST be respresentative (very similar sound velocity) of the material which you wish to inspect/measure. You can accept equivalence within but not across material groups, e.g. low alloy steels, austenitics, aluminium, copper. Find yourself a comprehensive table of sound velocities in various materials and get to know the percentage variations. : : Now the same applies whether you are calibrating single or twin crystal probes with the keywords in either case being: : : TRACEABILITY, ACCURACY, REPEATABILITY. : : As always watch out for careless and lazy assumptions creeping in, the major cause of disastrous measurement error. : : Cheers : : Nigel : : : this kind of question could be could there be any diferent between the calibration of a single element transducer and dual element transducer ------------ End Original Message ------------ Follow Ups: Post a Followup: Name: E-Mail: Subject: Comments: ----------- Start Original Message ----------- : Lanre, if your equipment is fitted with a single or twin option ensure that you are in the correct mode. With BOTH single and twin I would position the 1st backwall echo at zero on the timebase and the second and 3rd at 5 and 10 and then delay off so that the 1st BWE is on 5 and the 2nd on 10 (illustrative figures for compression wave only). That takes care of any delay line/perspex wedge sound path. : Tom Nelligan wrote some technical differences, i wrote that the concept of calibration is identical for both single and twin - traceability, accuracy, repeatability. : Enlighten me please Lanre, what has happened or been said that makes you concerned there may be a difference? : : nigel, if i get you right, all things being equal theres no different between calibrating with dual element transducer and single element transducer : : : Lanre : : : Aside form the technical differences which Tom has outlined, the philosophy of calibration must be the same no matter which tools you are using - namely, traceability, accuracy and repeatability. Before commencing calibration ensure you are familiar with all your equipment's characterisitics (read manufacturer's literature/operating manuals/technical references) and that it is undamaged and in good working order. Both the thickness meter or flaw detector, depending on which you are using) and the calibration block should bear valid calibration certificates and have passed the most recent proceduralised in-house checks as evidenced by a log record. The calibration block MUST be respresentative (very similar sound velocity) of the material which you wish to inspect/measure. You can accept equivalence within but not across material groups, e.g. low alloy steels, austenitics, aluminium, copper. Find yourself a comprehensive table of sound velocities in various materials and get to know the percentage variations. : : : Now the same applies whether you are calibrating single or twin crystal probes with the keywords in either case being: : : : TRACEABILITY, ACCURACY, REPEATABILITY. : : : As always watch out for careless and lazy assumptions creeping in, the major cause of disastrous measurement error. : : : Cheers : : : Nigel : : : : this kind of question could be could there be any diferent between the calibration of a single element transducer and dual element transducer ------------ End Original Message ------------ Optional Link URL: Example: "http://www....html". Alternative write "http://www.ndt.net/wshop/attach/filename.htm" if you transfered a filename.htm via FTP Page Title: is important! Optional Image URL: http://www....gif Attention! Please click the button only once. This may take a moment to process Forum Technical Discussions Help