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edwardnxs4
Oil&Gas Industry, Indonesia, Joined Dec 2013, 20

edwardnxs4

Oil&Gas Industry,
Indonesia,
Joined Dec 2013
20
10:16 Jun-03-2014
How to Increase Resolution of Ultrasonic Measurement

Hi Guys, Need Help..

I have case :
How there manufacturer claim their measurement resolution is 0.0025mm ?
it is define that the wavelength is 0.0025mm, right ?
with that wavelength mean the frequency about 2.3Ghz (in stainless steel 5800m/s) .
so they use 2.3Ghz Ultrasonic transducer ?

Or they get the resolution from some kind of signal processing ?

Thank you in advance
Edward

 
 Reply 
 
Linas Svilainis
R & D,
Kaunas University of Technology, Lithuania, Joined Nov 1998, 67

Linas Svilainis

R & D,
Kaunas University of Technology,
Lithuania,
Joined Nov 1998
67
14:44 Jun-03-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to edwardnxs4 at 10:16 Jun-03-2014 (Opening).

Hi Edward,

most probably resolution in your case is meant as "granularity" of readings. That is. what is the smallest increment/decrement step of your measurements. Usually should be adhered to accuracy (trueness+precision) of your measurements.

regards,

Linas

1
 
 Reply 
 
edwardnxs4
Oil&Gas Industry, Indonesia, Joined Dec 2013, 20

edwardnxs4

Oil&Gas Industry,
Indonesia,
Joined Dec 2013
20
05:18 Jun-04-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to Linas Svilainis at 14:44 Jun-03-2014 .

Hi Prof. Linas,

I actually wanted to ask this to you via email, but afraid you won't reply me...
Thank you for your reply in this topic, Prof .

So if this is a "granularity" of readings, I can reach 0.0025mm of resolution with 5 Mhz dual ultrasonic transducer, right ?

so if I want a high resolution of readings, so I need ADC with high sampling rate ?

but I still worry about the precision of the readings, the true thickness of the pipe.

Please read this article :
http://usra.ca/imageresolution.php

it is say "Because both target # 1(brown) and target # 2 (green) are hit by the same wave, both target objects are seen as one."

it mean how we can reach 0.0025mm resolution if the wavelength of 5Mhz is 1.16mm ? because all detection in that range will seen as one ..

Regards,
Edward

 
 Reply 
 
John Norman
Consultant, owner of business
NTS Ultrasonics Pty Ltd, Australia, Joined Oct 2012, 116

John Norman

Consultant, owner of business
NTS Ultrasonics Pty Ltd,
Australia,
Joined Oct 2012
116
10:31 Jun-04-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to edwardnxs4 at 05:18 Jun-04-2014 .

Hi Edward,

From the emails you sent me earlier, I think I know what you are trying to do, and my advice is to take on a consultant with experience in these areas. In the meantime, I can tell you that it looks like you may be confusing two different resolutions.

One type of resolution is being able to identify two closely spaced echoes and your comments on wavelength, etc apply. Another type of resolution is the accuracy of the measurement of the arrival time of an echo, which is probably what you want for monitoring corrosion in pipes. Very high digitizing rates are impractical because very high speed electronics is difficult to design and expensive, and probably unnecessary for corrosion mapping with fixed transducers. You only need GHz sampling for single shot measurements to capture very fast events. Nothing happens fast in corrosion - grass grows faster. You can easily have multiple measurements from each transducer and there are various "tricks" that can be used to improve resolution. You might find it useful to Google "equivalent time sampling" which is used in many oscilloscopes to achieve high resolution.

Regards
John Norman

1
 
 Reply 
 
Frank Lund
R & D,
United Kingdom, Joined Apr 2005, 221

Frank Lund

R & D,
United Kingdom,
Joined Apr 2005
221
14:52 Jun-04-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to edwardnxs4 at 05:18 Jun-04-2014 .

Edward,

For a thickness tester you don't need an ADC, you can simply use a fast threshold detector (an analogue comparator) to convert the received signal into a digital pulse signal that can be measured by a timer/counter with a fast clock.

Cheers,
Frank

1
 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
15:04 Jun-04-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to edwardnxs4 at 05:18 Jun-04-2014 .

"So if this is a "granularity" of readings, I can reach 0.0025mm of resolution with 5 Mhz dual ultrasonic transducer, right ?"

No, not with that type of transducer and not with any common off-the-shelf thickness gages. As a practical matter, you would need a very high frequency (50 MHz or higher) broadband single element transducer (not a narrowband dual) with a high bandwidth pulser/receiver and a very high frequency digitizer capable of accurately capturing the peak of the signal. For example, we formerly sold a specialized thickness gaging system that used 100 MHz broadband transducers with a 200 MHz bandwidth pulser/receiver and a 2 GHz digitizer with signal averaging. That system was capable of the level of resolution you're asking about, but note the specification of all three components.

Also, referring back to your original question, beware of misleading definitions in equipment specifications. For example, "resolution" may mean "display resolution" rather that "measurement resolution". You can build an instrument that will display readings to ten decimal places, but that doesn't make the numbers meaningfu!

1
 
 Reply 
 
Linas Svilainis
R & D,
Kaunas University of Technology, Lithuania, Joined Nov 1998, 67

Linas Svilainis

R & D,
Kaunas University of Technology,
Lithuania,
Joined Nov 1998
67
00:28 Jun-05-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to edwardnxs4 at 05:18 Jun-04-2014 .

Hi Edward,

please read the following :
https://www.e-education.psu.edu/natureofgeoinfo/book/export/html/1620
http://www.ndt.net/article/wt1097/hammond/hammond.htm
http://www.howequipmentworks.com/physics/medical_imaging/ultrasound_imaging/ultrasound.html
http://www.science.mcmaster.ca/medphys/images/files/courses/4T03/4T3_ultrasound.pdf

regards,

Linas

1
 
 Reply 
 
edwardnxs4
Oil&Gas Industry, Indonesia, Joined Dec 2013, 20

edwardnxs4

Oil&Gas Industry,
Indonesia,
Joined Dec 2013
20
10:10 Jun-11-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to Linas Svilainis at 00:28 Jun-05-2014 .

To Mr.John :
Yes you are right, I have much time to do multiple measurements,
but Ghz sampling IC is has very complicated pinout and Ghz sampling is require very high speed electronic (difficult & expensive).

To Mr.Frank :
How fast the comparator ? 10ns is enough ?

To Mr.Tom :
High frequency results low penetration and short wavelength, but increase the resolution but it is for your application, I have to know the optimum frequency for my application.

To Mr.Linas :
Thank you for your reference

To all :
anyone know how to calculate range of measurement ?
example, how the minimum and maximum thickness of 10 Mhz of transducer ?
for the minimum is same like its wavelength ? but how about the maximum ?
is there any calculation or I need to do some direct examination ?

 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
16:05 Jun-11-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to edwardnxs4 at 10:10 Jun-11-2014 .

"example, how the minimum and maximum thickness of 10 Mhz of transducer ?
for the minimum is same like its wavelength ? but how about the maximum ?
is there any calculation or I need to do some direct examination ?"

The minimum and maximum measurable thickness with a given transducer in a given case will depend on the acoustic properties of the test material and the instrument setup as well as the transducer type (including bandwidth). So there is no single answer. Narrowband transducers will typically have greater penetration than broadband transducers of the same frequency, while broadband transducers will have better thin material resolution. Instrument hardware and setup will have a major influence on range. If you need exact numbers, you will need to determine that experimentally for your specific transducer/instrument/setup/material combination. For more general numbers, the manufacturer of your transducer may be able to provide estimates. For example, we publish this chart of *general* ranges for our broadband transducers used with our gages under the recommended setups:

http://www.olympus-ims.com/en/ndt-tutorials/thickness_gage/transducers_range/

1
 
 Reply 
 
edwardnxs4
Oil&Gas Industry, Indonesia, Joined Dec 2013, 20

edwardnxs4

Oil&Gas Industry,
Indonesia,
Joined Dec 2013
20
03:46 Jun-12-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to Tom Nelligan at 16:05 Jun-11-2014 .

Could you give me the example formula/calculation, please..

Because I can't found it on internet,
But my guess , I need to know the attenuation/length , but The attenuation is SUM from some parameters, such as : Frequency, Acoustic impedance of material under test, maybe Amplitude of the wave, temperature , transducer mechanical setup, etc.
and the advantage is the material undertest is Homogen, Steanless Steel

 
 Reply 
 
edwardnxs4
Oil&Gas Industry, Indonesia, Joined Dec 2013, 20

edwardnxs4

Oil&Gas Industry,
Indonesia,
Joined Dec 2013
20
03:55 Jun-12-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to Tom Nelligan at 16:05 Jun-11-2014 .

and whether the transducer range that you gave to me is valid for dual element transducer? , Because I will use 5MHz or 10 MHz dual element transducer.

 
 Reply 
 
edwardnxs4
Oil&Gas Industry, Indonesia, Joined Dec 2013, 20

edwardnxs4

Oil&Gas Industry,
Indonesia,
Joined Dec 2013
20
04:06 Jun-12-2014
Re: How to Increase Resolution of Ultrasonic Measurement
Oops, I am sorry, it turns out there are a range for the dual element transducer ..
But please, I want to know the calculation if you do not mind ...

thank you
 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
15:09 Jun-12-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to edwardnxs4 at 04:06 Jun-12-2014 .

As I wrote above, for an exact answer you need to test your specific material. That is especially true in the case of stainless steel, where grain size is a major factor. With an appropriate material sample you should be able to select an optimum transducer in just a couple minutes.

"The attenuation is SUM from some parameters, such as : Frequency, Acoustic impedance of material under test, maybe Amplitude of the wave, temperature , transducer mechanical setup, etc."

Exactly... at a minimum you need to know transducer frequency and bandwidth, the attenuation coefficient of your test material, and the performance characteristics of the pulser/receiver you are using. That is why theoretical calculation of effective range is seldom practical except in a very general way.

The charts that we publish are intended as a starting point or guideline for our customers. That is all any chart of that sort can be, because exact ranges in a given case will vary according to the factors that we list on that web page. The numbers in our chart are based on actual testing. The steel ranges are based on testing with 4340 carbon steel and the plastic numbers are based on testing with high density polyethylene, using an Olympus Model 38DL PLUS thickness gage with an optimized setup for each transducer.

 
 Reply 
 
edwardnxs4
Oil&Gas Industry, Indonesia, Joined Dec 2013, 20

edwardnxs4

Oil&Gas Industry,
Indonesia,
Joined Dec 2013
20
10:23 Jun-16-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to Tom Nelligan at 15:09 Jun-12-2014 .

Why there is no range of thickness information for High Frequency Ultrasonic ? it's single or dual element ?
http://www.olympus-ims.com/en/ultrasonic-transducers/highfrequency/

I guess it's will be narrow of range and very low penetration, and maybe the echo need to amplify 100 time.

I want to build corrosion sensor , So I just need to Boost Axial resolution to get data quickly for corrosion rate calculation. could you tell me more detail , why I can't get 0.0025mm resolution if using 5 Mhz / 10 Mhz transducer ? most people here said , the key of get high resolution is on Digital Signal Processing.

Could you explain the ratio of 2 of them (transducer and DSP) to get resolution.

sorry for those Question,
because still confuse about this.

Thank you in advance
Edward

 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
14:57 Jun-16-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to edwardnxs4 at 10:23 Jun-16-2014 .

"Why there is no range of thickness information for High Frequency Ultrasonic ?"

Because range in a given case is so highly dependent on the acoustic properties of the test material and the type of pulser/receiver being used. Generalized tables would not be very useful. See this paper for further details:

http://www.olympus-ims.com/en/applications/specifying-high-frequency-ultrasonic-transducers/

These 50+ MHz transducers are definitely not designed for corrosion survey applications, so I would not recommend them to you in this case. They are normally used for high resolution C-scan imaging, thin layer thickness measurement, and material analysis in thin, transmissive materials. Effective penetration in rough, corroded metal will be minimal. As a practical mater, I am skeptical that you will be able to reliably measure thickness to *meaningful* 0.0025 mm resolution under field conditions at conventional UT frequencies, but since I do not work in the field of DSP development I'll leave discussion of that approach to those who do.

 
 Reply 
 
edwardnxs4
Oil&Gas Industry, Indonesia, Joined Dec 2013, 20

edwardnxs4

Oil&Gas Industry,
Indonesia,
Joined Dec 2013
20
11:30 Jun-17-2014
Re: How to Increase Resolution of Ultrasonic Measurement
In Reply to Tom Nelligan at 14:57 Jun-16-2014 .

"No, not with that type of transducer and not with any common off-the-shelf thickness gages. As a practical matter, you would need a very high frequency (50 MHz or higher) broadband single element transducer (not a narrowband dual) with a high bandwidth pulser/receiver and a very high frequency digitizer capable of accurately capturing the peak of the signal."

Okay then , that recommendation not suitable for my application, so I know , that is possible to get high resolution measurement just using few Mhz transducer with some Digital Processing..

And for what you said about "meaningful number" , I think it will be , because the main idea of corrosion sensor (for my application) is how to get Corrosion rate as soon as posible

 
 Reply 
 

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