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This is useful, for example, in gaging remaining thickness over internal passages in turbine
blades.  Procedures for using immersion transducers are outlined in Section 4.3.2.4, below.

Metals with Thicknesses Ranging from 0.030 inch (0.76mm) Upward.

Single Element Contact Transducers Hard-Faced Wear Plates.

Depending upon active element size and frequency, highly damped (broadband) transducers of
this type can seldom be used on steel or aluminum much below 0.030 inch (0.8mm).  The ultimate
minimum thickness limitation must be determined experimentally.

The advantage of using this type of transducer is that much thicker sections can be gaged, and on
materials that have less than smooth surfaces or are relatively attenuative.  Again, some
experimentation will indicate the limitations and advantages among transducers of the same type,
but having different sizes, frequencies and spectral characteristics.

When trying to achieve best results on relatively thin materials, the most important considerations
are frequency and spectral characteristics.  Foremost is the need to use a transducer having the
greatest bandwidth, all other things being equal.  Such transducers have relatively large, high
density masses bonded to the internal face of the active element.  This mass minimizes the
amount of "ringing" of the active element following excitation by a short duration, high voltage
electrical pulse.  This kind of high mechanical damping minimizes the length of the ultrasonic
wavetrain associated with the high energy initial pulse as well as the subsequent back-wall echos.

Also necessary to achieve best thickness resolution is the need to use the highest frequency
consistent with external factors that affect coupling efficiency, and to take material attenuation into
consideration.  IF a transducer is expected to produce minimum thickness resolution and be used
over a broad range of thicknesses, test material attenuation may dictate a compromise. While
higher frequencies produce thinner thickness resolution, attenuation is more pronounced at higher
frequencies.

For relatively flat, smooth-surfaced steel or aluminum test objects, highly damped contact
transducers in the frequency range from 5 to 10 MHZ generally will produce acceptable results in
the thickness range from 0.040 inch (1.0mm) up to 5 inches (125mm) more or less.  With
QFT-100, and under ideal external conditions, transducers of 5, 7.5 or 10 MHZ having active
elements of 0.25 to 0.50 inch (6.4 to 12.7mm) diameter will cover the range from 0.030 to 10
inches (0.76 to 250mm) or more.

For procedures outlining the use of broad banded contact transducers, see Section 4.3.2.1.

Single Element Contact Transducers with Membrane and Other Protective Devices.

So-called protected element transducers are used in relatively rugged applications involving
rough, abrasive test object surfaces or surfaces at elevated temperatures.  Usual designs of
protected element transducers include reduced internal damping, lower frequencies and larger
diameters.  As a result, their application typically ranges from a few tenths of an inch (10mm plus
or minus) upwards.

Often used on castings, forgings and mill-finished piping, protected element transducers are
infrequently used for thickness gaging -- more often used for flaw detection.  However, if the
protective element is a relatively thin elastomer or flexible polymer, the procedures for thickness
gaging are similar to those for single element contact-type transducers.  For thicker wear-caps or
temperature-protective delay lines, procedures are more like those for delay line transducers.

Dual Element Contact-Type Transducers.

This category of transducers is frequently used in thickness gaging applications, combining some
of the advantages of both single element contact and delay line models.  They have two elements,
each with a separate delay line, mounted side-by-side in a single fixed housing.  The elements are

Summary of Contents for TG400

Page 1: ...ERATOR S MANUAL TG400 Ultrasonic Thickness Gage Featuring SplitView SplitScan AutoTrack NDT Systems Inc 17811 Georgetown Lane Huntington Beach CA 92647 Phone 714 893 2438 FAX 714 897 3840 Rev 1 0 07 0...

Page 2: ...may have a question with C Chapter 2 deals with the menu structure a description of the features This would be recommended reading There are a few images to help you better understand the concepts C C...

Page 3: ...0 000 nanoseconds Synchronization IP Initial Pulse IF Interface Delay Transducer Modes Single or dual element Display Modes RF positive negative full wave rectified Flaw Mode Two 2 gates selectable po...

Page 4: ...ypical depending upon display back light usage 3 AA NiMH furnished Battery Charger 5 hours for full charge Transducer Cable Lemo Connectors Connectors Size Top Section 3 25 W x 7 L x 1 4 D Weight Incl...

Page 5: ...ety of keys menu selections are available to change continuous variables such as range delay gate positions alarm levels and reject SCROLLING When a key is continuously depressed to change a variable...

Page 6: ...A free catalog will be sent on request by contacting Customer Information at NDT Systems Inc 17188 Georgetown Lane Huntington Beach CA 92647 phone 714 893 2438 FAX 714 897 3840 In many cases equivale...

Page 7: ...plit Opt1 is reserved for future use MENU FLOW The following represents the menu flow of the TG400 Pressing the MENU ESC key repeatedly will sequence through the menus as shown Note The branch if menu...

Page 8: ...using many kinds of transducers to be successfully performed highly precise flaw detection tests may require refinements to the default variables to better match transducer instrument characteristics...

Page 9: ...useful ness of this feature would be evident on material with varied attenuation properties such as painted and non painted surfaces or corroded back surfaces AGC may also help overall reading accura...

Page 10: ...rease or Decrease the Measurement Threshold level Any echo or echo half cycle with amplitude equal to or greater than the Thickness Gate Threshold will be measured The threshold gate is the bar on the...

Page 11: ...vide optimal personal viewing BACKLIGHT BKLT Turns the backlight to AUTO ON or OFF Auto will turn the backlight on while making measurements OO will turn the backlight on continuously and OFF will lea...

Page 12: ...can not exceed the set Range of the Main Trace window For instance if the Main Trace is set to 3 the Track window can not be set to 4 Usually the Track window is something like 20 40 of the Main Trac...

Page 13: ...12 12 instrument setups Note If the gage is powered ON with the ENTER button depressed the Factory Default setup will be loaded...

Page 14: ...at the water path to the IF will be seen as well as the IF to destination target back wall Be sure this rule stays in place throughout the water path change probability It is OK to select a long MAIN...

Page 15: ...es However such transducers will be relatively expensive and not readily attainable Standard inexpensive delay line transducers highly damped in the frequency range of 10 to 20 MHZ will ordinarily pro...

Page 16: ...nd be used over a broad range of thicknesses test material attenuation may dictate a compromise While higher frequencies produce thinner thickness resolution attenuation is more pronounced at higher f...

Page 17: ...llic Test Materials Virtually all the techniques and applications described above can be applied to a host of non metallic and composite materials It is not possible to cover the numerous applications...

Page 18: ...way of observing these effects and to become quickly familiar with TG400 s controls is to perform the following procedure 1 Attach a highly damped broadband transducer such as the OPTIMA CHG053 or NO...

Page 19: ...ive gain accordingly 11 To become familiar with the RANGE function position the cursor at RNG The up arrow key will squeeze the echos on the A trace to the left that is except for the initial pulse If...

Page 20: ...t this point use the Up Dn arrow keys to change the length of the IP BLK gate in order to observe the effects of the control 16 The IF BLK interface echo blocking functions in a similar fashion as the...

Page 21: ...Thickness readout the upper range calibration is complete Note that zero may change through up to 5 or 10 counts on the display before the indicated thickness changes Choosing zero roughly at the mid...

Page 22: ...when using single element transducers with thin elastomeric membranes or on coated test objects 23 Cursor to ECHO BLOCKING GATE ECHO BLK Note the thick horizontal bar on the Thickness gate Use the rig...

Page 23: ...ponents This mode of display RF reveals all the details of the signal If necessary to more faithfully reproduce the waveform in the figure above it may be necessary to key to GAIN and change the gain...

Page 24: ...ange of the TG400 has been set to a long range and the RF display is selected there will be poor detail in the presentation of the RF In order to expand the RF display of the back echo under such cond...

Page 25: ...he constant distance paths taken by the sound beam in traversing the dual delay lines a measurement can be made of the travel distance in the test object only Since the sound beam travels at a slight...

Page 26: ...O to produce the thickness readout corresponding to a known thickness in this case 0 500 inch Note when you check the measurement of the 0 200 inch step note it produces 0 205 inch This error is due t...

Page 27: ...0 If it close adjust the VEL to adjust to exact material velocity Option B Connect TG506 Transducer From MAIN Menu Select SETUP and PICK the appropriate transducer from the list Press ZERO ECHO front...

Page 28: ...n this case the ECHO BLK will need to be extended out far enough to pass the multiple echo cycles of the first echo This will limit the low end thickness capability In the lower image a TG560P transdu...

Page 29: ...ve right when you move the cart to the left the B Scan Cursor move to the right ENCODED L L Left to Left When you move the cart to the right the B Scan Cursor move right when you move the cart to the...

Page 30: ...on screen from the thickest area to the thinnest area of your sample 2 Go to the SETUP Menu and select the PX506 if it is shown If not select TG506 This should set the instrument up in general terms A...

Page 31: ...ld not have to go through the extra steps 11 Once calibrated press the B SCAN Key 12 Cursor to TYPE and use the Up Dn arrows to select T SCAN This will provide a Cross Section view of the area being i...

Page 32: ...racteristics such as the presence of scattering reflectors impedance an isotropy Modula and other physical and mechanical properties all interact with ultrasonic sound beams somewhat differently than...

Page 33: ...AA style batteries inserted into the bottom panel via the rear panel access cap The gage is charged via an external battery charger Once fully charged the TG400 will run for up to 20 hours before req...

Page 34: ...ng optional TG400 accessories are available ATRP1 TG400 Carry Pouch A light weight leatherette protective case The TG400 fits firmly into a case like compartment supported at an adjustable angle stand...

Page 35: ...exclusive remedy provided herein fails of its essential purpose or operates to deprive either party of the substantial value of its bargain then the Purchaser s exclusive remedy will be the return of...

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