Foros de discusión de Olympus sobre los END

Q: temperature in material, transducer, coupling, is important, calibration (wizard) now my hand (30 degree) will heat the transducer so there is a different in the temp. from the start of my calibration, so to Maintain accuracy in the measurement I will have to recalibrate at each point ? or am I wrong ? my velocity in the transducer and/or probe, will decrease when it is heated
And so will my readings ? is there a way to insure a accuracy in all readings.

best regards
j.schmidt

Sound velocity in all materials changes with temperature, so for maximum accuracy you must recalibrate velocity for the temperature at which you are working. Sound velocity usually decreases as temperature increases. However if the material temperature is only around 30 C, this change will likely be very small with respect to normal environmental temperature.

Whether you must recalibrate zero as well depends on the type of transducer that you are using. If it is a single element contact transducer (which must not be used on surfaces hotter than 50 C) or a delay line transducer used for echo-to-echo measurement, zero recalibration is generally not necessary. If it is a dual element transducer, then you should recalibrate to compensate for velocity chnages in the transducer's delay line. Again, if you are working around 30 C this change is likely to be very small.

You may wish to read our application note on high temperature testing:
http://www.olympus-ims.com/en/ndt-application/183-id.209715235.html

Yes, we know this is a source of variations in ultrasonic inspection, and all these effects are known. The biggest problem is the plastic wedge, which is much more sensitive to temperature than the metal.

The code-accepted procedure, e.g. in pipeline AUT, is to keep the temperature of the cal blokc within +/- 10 degrees Celsius of the component. That reduces the emp effects considerably.

Michael Moles

How do i get the celcoat thickness with the OMMNISCAN MX (off course question )

Mr. Schmidt, are you referring to the very thin acrylic coating commonly found on fiberglass? (I am familiar with that material under the name "gelcoat".) If so, the common approach is to use a single-element 20 MHz delay line transducer such as a Panametrics-NDT V208 or M208. We have an application note on the subject:

http://www.olympus-ims.com/en/ndt-application/183-id.209715259.html

Most commonly this measurement is made with one of our precision thickness gages, but you can certainly use an Omniscan MX in conventional UT mode. Measure thickness from the delay line echo to the gelcoat/fiberglass echo as shown in the waveforms in that app note.