AENDT SW6 Ultrasonic Thickness Gage User Manual

AENDT SW6 Ultrasonic Thickness Gage

OVERVIEW

Thank you for using QingCheng’s Ultrasonic Thickness Gauge. Please read the operating manual in detail before use as this will enable you to use the gauge in the shortest amount of time. The manual includes information on the functions, specifications, settings, operation and calibration of the gauge.

SPECIFICATIONS

SW6/SW6U: large range, high-resolution mode, measuring range of 0.65mm～ 500mm, display resolution of 0.01mm, capacity for data storage.
SW7: large range, high-resolution mode, through-coat mode, measuring range of 0.65 mm~500 mm (standard), 3.0～50mm (through-coat mode), display resolution of 0.01mm.

Table 1-1: SPECIFICATIONS

| SW6| SW7
---|---|---
Measuring Range (Standard)| __

0.65～500mm

Measuring Range (Echo-Echo)| __

__

–

| 3.0～50.0mm

__

(Steel, depend on probe)

Low Limit of Pipe

__

(Pipe Wall)

| Φ15mm×1.0mm (7.5MHz,Φ6mm)

__

Φ10mm×1.2mm(7.5MHz, Φ6mm)

__

Display Resolution

| 0.01mm/0.001inch
Material Velocity| 509～18699m/s
Measurement Resolution| __

±(0.5%H+0.05) mm

__

Bandwidth

| __

1MHz～10MHz(-3dB)

Measuring Rate| 2～20 times/sec(optional)
__

Power Supply

| __

3VDC (two AA batteries)

__

Work Time

| 280 H(auto)

100 H (backlight on)

__

Screen

| __

128×64 LCD

Size| 136(L)×72(W)×20(H)mm
Weight| 176g (including battery)
Work Temperature| -10～﹢50℃ (with high-temperature probe, up to 300℃)
Work Humidity| 20%～90%RH
---|---

FEATURES

• Measuring ranges from 0.65mm to 500mm (dependent on the gauge, probe and material).
• Suitable for different types of probes.
• Material velocity can be chosen or inputted directly. An unknown velocity can be found automatically by one-point or two-point velocity calibration.
• Numerous kinds of measurement modes: standard, scan, alarm, difference, high-temperature (match high-temperature probe), average, pipe-wall, echo-echo.
• Special pipe wall measurement mode improves the measuring accuracy of curved surfaces.
• Auto-matching makes the gauge suitable for various materials including metal, glass, plastic, rubber and gray cast.
• High-capacity data storage (the U model) for up to 2000 data sets.
• Normal measurement can be done using function keys without need to open menu.

INCLUDED COMPONENTS & PROBE SELECTION

Table 1-2: INCLUDED COMPONENTS

Table 1-3: PROBE SELECTION

Probe Type| Measuring Range| Work Temperature| Description
---|---|---|---
5M,Ф10| 0.7～400mm

3.0～50mm(through coat)

| -10～+50℃| Basic

(Suitable for through coat)

5M,Ф6| 0.70～60mm| -10～+50℃| Little Pipe Wall
2.5M,Ф12| 3.0～500mm| -10～+50℃| Basic
7.5M,Ф6| 0.65～25mm| -10～+50℃| Mini Pipe Wall
7.5M,Ф10| 0.65～250mm| -10～+50℃| High Resolution
ZW5P| 4.0～80mm| -10～-300℃| High Temperature
2M,Ф22| 3～50mm

(Gray Cast)

| -10～+50℃| Gray Cast

Note: Measurement range depends on the probe, material, structure, surface condition, and so on. High-temperature tolerance depends on the probe property and couplant.

INTRODUCTION OF THE GAUGE AND BASIC OPERATION

THE MAIN UNIT
The main unit of the gauge is shown in Figure 2-1:

KEYPAD
The keypad is shown in Figure 2-2:

The function of each key is explained below:

• This key is used to power on the gauge and simultaneously carry out self-checking; turn directly to the measuring GUI when in the menu or sub-menu; power off in the measuring GUI (long press).
• This key is used to save or cancel data in the measuring GUI; turn to the next page in the main menu.
• This key is used to: open the sound velocity table or enter velocity; shift the cursor left when adjusting readings or when in the main menu.
• This key is used to: open the measurement mode menu; and shift the cursor right when adjusting readings or when in the main menu.
• This key is used to: carry out a one-point calibration for sound velocity in the measuring GUI; increase the indicated value or shift the cursor up in the main menu.
• This key i s used to: carry out a two-point calibration for sound velocity in the measuring GUI; decrease the indicated value or shift the cursor down in the main menu.
• This key is used to: turn the backlight on or off in the measuring GUI; to confirm your setup or menu selection.
• This key is used to open the main menu from the measuring GUI or return to the menu.

BASIC OPERATION
The purpose of this section is to demonstrate how basic measurements can be made with the gauge. The unit has been shipped from the factory with the following default conditions:

• SOUND VELOCITY: 5900m/s (approximate sound velocity for the steel test bar provided with the gauge) (see “Note” below)
• BACKLIGHT: ON
• UNITS: mm/inch
• LANGUAGE: ENGLISH
• MEASUREMENT RATE: 4 times/s
• DISPLAY RESOLUTION: 0.01mm/0.001inch

A further explanation of these default conditions can be found in later sections of this manual. It is recommended that they only be changed by the operator after they have become familiar with the more sophisticated features of the gauge.
Note: The default value for sound velocity is only an approximation of the sound velocity in the test block material. The sound velocity of stainless steel is typically 5663m/s. Therefore, if you find the default value gives inaccurate results on your material, please refer to Section 3 for calibration instructions.

INITIAL SETUP
In this section, the general operation procedure when in the standard measurement mode will be introduced. Please follow this procedure when operating the gauge for the first time.

• STEP 1: Plug the probe into the gauge at the top end of the gauge.

• STEP 2: Power on the gauge by pressing . The ON GUI and measuring GUI will appear in turn (initial setup as shown in Figure 2-3). The gauge will auto-recover the setup from the previous use.

• STEP 3: Velocity Input or Zero Calibration.
  Material velocity must be correct when doing measurements. If the velocity of the material to be measured is known, please input it first (refer to Section 3.1), otherwise, the velocity should be calibrated. To calibrate the velocity, refer to Section 3.2. Following this, zero calibration should be carried out (refer to Section 3.1).

• STEP 4: Measurement
  Firmly couple the probe to the surface of the material to be measured. Ensure couplant is applied at the point of contact (refer to Section 2.3.2 for more detail on measurement).

• STEP 5: Save
  Refer to Section 4.1.2

• STEP 6: Upload data (suitable for USB gauge)
  To upload the saved data to the computer for processing, complete the following:

MAKING MEASUREMENTS

• STEP 1: Apply couplant to the test block or material at the spot to be measured. In general, the smoother the material surface, the thinner the couplant may be. Rough surfaces require more viscous couplant such as gel or grease. Special couplant may be required for high-temperature applications.
• STEP 2: Press the tip of the probe to the surface of the material to be measured. Use firm pressure and keep the probe as flat as possible on the material surface.
• STEP 3: Read the material thickness on the gauge display.
  • Note: For the highest accuracy, the velocity of the material must be correct. Refer to Section VELOCITY SETUP for this procedure.

CALIBRATIONS

Calibration is the process of adjusting the gauge so that it measures accurately on a particular material using a particular probe at a particular temperature. Calibration should be carried out when using the gauge for the first time or when probes are changed. Below are the gauge’s various calibration procedures.

ZERO CALIBRATION
If the probe’s zero is not calibrated correctly, all measured values will have a fixed error. When the probe’s zero is calibrated correctly, the unit can measure the fixed value and correct all subsequent measurements accordingly. To zero calibrate, follow the below operation:

• STEP 3: Clean the probe surface and apply couplant to the test block that corresponds with the inputted thickness.
• STEP 4: Couple the probe to the block and the gauge will automatically return to the measuring GUI when calibration is completed after a few seconds.

The measured thickness value while coupled to the thin calibration block should be within ±0.20mm of the correct thickness. If the indicated thickness is two or more times the actual thickness of the thin calibration block with a good approximate sound velocity, the gauge is “doubling” (ie. measuring to the 2nd or 3rd multiple echo). Do not attempt to do a ‘Zero’ or a ‘Velocity and Zero’ calibration under this condition. Instead, correct the cause of the doubling before calibrating again: either the calibration block is thinner than the specified capability of the probe, the probe is malfunctioning, or the gauge is malfunctioning.

MATERIAL VELOCITY CALIBRATION
In order for the gauge to make accurate measurements, it must be set to the correct sound velocity depending on the material being measured. Different types of materials have different inherent sound velocities: for example, the velocity of sound through steel #45 is approximately 5900m/sec, whereas that of stainless steel is approximately 5663m/sec (a further list of ultrasonic velocities of common materials can be found in the Appendix 1). If the gauge is not set to the correct sound velocity, all of the measurements made by the gauge will be erroneous by a fixed percentage.

ONE POINT CALIBRATION
Material velocity calibration of a material can be done by using a thick test block (with a known thickness) of that exact material. Calibration must be performed for each new type of material where the sound velocity is unknown. The procedure is outlined below:

• STEP 1: Press to enter the BLOCK THICKNESS GUI
• STEP 2: Press to input the known thickness of the test block.
• STEP 3: Press to proceed to the next step.
• STEP 4: Clean the probe surface and apply the couplant to the test block.
• STEP 5: Couple the probe to the test block and the gauge will return to the measuring GUI when calibration is completed after 4 seconds.

WO POINT CALIBRATION
Material velocity calibration of a material can also be completed by using both a thin test block and a thick test block (with known thicknesses) of that exact material. It requires that the thickness of the material to be measured be within the range of the thicknesses of the two test blocks. This method can reduce non liner error and obtain a result of higher precision. The procedure is outlined below:

• STEP 1: Press to enter the THIN BLOCK GUI.
• STEP 2: Input the thin block’s thickness using .
• STEP 3: Press to enter the THICK BLOCK GUI.
• STEP 4: Input the thick block’s thickness using .
• STEP 5: Press to enter the CAL THIN BLK GUI.
• STEP 6: Clean the probe surface, apply couplant to the thin test block, couple the probe to the thin test block and when the reading is stable for 4 seconds the gauge will automatically proceed to the CAL THICK BLK GUI;
• STEP 7: Immediately couple the probe to the thick test block and when the reading is stable for 4 seconds the GUI will display CAL COMPLETE. Following this, the gauge will return to the main menu

SET THE VELOCITY AS A KNOWN VELOCITY

• Press to open the velocity table and set the velocity using and. If the exact
• velocity of a material is known, you can also press to open the INPUT VELOCITY GUI and directly input the velocity using
  • Note: Ensure the probe and block are coupled tightly.

FUNCTION AND SETUP

MAIN MENU

• Press to open the main menu (shown in Fig. 4-1).

MAIN MENU1

• ECHO-ECHO
  SAVE LIMIT UNITS SCAN DIFF HTEM AVG [SHIFT] Next Page 1

MAIN MENU2

• STD
  RESL RATE AUTO-OFF RESET CONTR LANGUAGE [SHIFT] Next Page 2

MAIN MENU3

• PROBE-ZERO-CAL
  MANU- SELECT-PRB Sound ROTATE [SHIFT] Next Page 3
  

MAIN MENU4

• CAL-1
  BACK-LIGHT CAL-2 DIAMETER Velocity Preset [SHIFT] Next Page 4

MODE MENU：

• MEASURE MODE:
  STD SCAN ALM DIFF HTEM AVG DIM ECHO-ECHO

Fig. 4-1: Main menus 1-4 and measurement mode menu of the SW7 models

ECHO-ECHO (ECHO-ECHO MEASUREMENT MODE)
If you want to measure a material covered with paint, please select this measurement mode.
SAVE (DATA PROCESSING)
SAVE has five options including CHECK, UPLOAD, DEL-ALL, DEL-GRP, and SAVE-SET. Use to navigates between the options.

CHECK

To view your co mpleted measurements, select SAVE in the main menu and then select CHECK using The group and serial number can be inputted using

UPLOAD (suitable for USB gauge

To transmit all measurement readings to a PC via USB, follow the procedure as below:

• STEP 1: Install the driver on the PC.
• STEP 2: Connect the gauge and the P C with the USB cable.
• STEP 3: Right click on “My Computer”, select “Manage”, then select “Device Manager”. Find the port of the connected gauge and remember its name.
• STEP 4: Start “SeriePort.exe” and select the port of the connected gauge.
• STEP 5: Select UPLOAD on the menu of the gauge and press . “CONNECTING” and “UPLOADING” will be indicated on the
• STEP 6: Click “RECEIVE” in the window of SeriePort.exe to transmit all measurement readings to the PC. When completed, the display of the gauge will flash “DONE” and automatically return to the menu, indicating completed data transmission.
• STEP 7: Click “SAVE” in SeriePort.exe to store the data in the PC (.txt form at).
  • Note 1: If the gauge can’t be powered on normally when it is connected to PC, please disconnect the gauge and power it on again.
  • Note 2: If “FAIL TO OPEN THE PORT” is displayed when “RECEIVE” is clicked (in STEP 6), STEP 5 has not been carried out properly.
  • Note 3: To protect your computer, exit “SeriePort.exe” before disconnecting the gauge.

DEL ALL

Delete all the data saved in the gauge’s memory using . Note that deleted data can’t be recovered.

DEL GRP

• Delete selected data saved in the gauge’s memory using . Note that deleted data can’t be recovered.

SAVE SET

This option activates the manual save mode for a data set. First, set the size of each data set according to your requirements (five measurement readings are saved under the default setup). The maximum data storage capacity of a single set is 99. The procedure is outlined below:

• STEP 1: Select SAVE SET in the main menu using
• STEP 2: Set the data size of your set using
• STEP 3: Press to returns to the measuring GUI and press . [SV:05] will be displayed on t he right of the screen.
• STEP 4: Make your first measurement. [NO:01] will be displayed on the right of the screen under [SV:05].
• STEP 5: Make the second measurement. [NO:02] will be displayed on the right of the screen under [SV:05]. •
• STEP 6: Continue making measurements until the set is completed, after which the display on the right of the screen will disappear.
• STEP 7: Press again to save the next set, and r epeat steps 4 to 6.
  • Note 1: Before measuring the next data set, wait for the coupling flag to app ear after the first data set is completed.is pressed repeatedly.
  • Note 2: The reading will be stored repeatedly if is pressed repeatedly.

LIMIT (ALARM MEASUREMENT MODE)
In this mode, the user will be notified when the measurement either drops below a lower limit or exceeds an upper limit. To set the lower and upper limits, select LIMIT in the main menu using   set the upper limit using and press to complete. Now set the lower limit using and press to complete. The measuring GUI is shown in Figure 4-2.

UNITS

The measured thickness can be displayed in either inches or millimeters. To change from one unit to the other, press to enter the main menu, select UNITS using and select either ‘mm’ or ‘inch’ using The current units in use are indicated on the right of the standard measurement GUI (see Figure 2-3).
Note: If the gauge is turned off before the key is pressed, the units will not be changed.

SCAN (SCAN MEASUREMENT MODE)
Whilst the material is being measured by the probe, the gauge can record the smallest and largest values. To activate this mode, select SCAN using slowly drag the probe along the surface of the material (ensuring good coupling) (the measurement GUI is shown in Figure 4-3).

DIFF (DIFFERENTIAL MEASUREMENT MODE)
Differential mode can be used to measure the difference between the tested object’s thickness and that of the reference value. Follow the procedure below:

• STEP 1 : Select DIFF using o change the reference value using (the default value is 10mm).
• STEP 2: Press to complete and return to the main menu.
• STEP 3: Press to return to the differential measuring GUI (as shown in Figure 4-4), and the set reference value will be displayed at the top left of screen.
• STEP 4: Measure the object and the difference in thickness of the measured material compared to the reference value will be displayed. The symbol “-” will be displayed at the top right when the difference is negative.

HTEM (HIGH TEMPERATURE MEASUREMENT MODE)
To measure the thickness of a high temperature object, select an appropriate high temperature probe where the temperature of the measured object is within the working temperature range of the probe. Please refer to the following procedure: select HTMP using enter the setup GUI. Input the material’s temperature using and press to complete and return to the main menu (the high temperature measuring GUI is shown in Figure 4-5).

AVG (AVERAGE MEASUREMENT MODE)

Average mode is used to measure the average of several completed measurements. The size of your data set can range from 2 to 99. To operate this mode, follow the below procedure:

• STEP 1: Select AVG in the main menu using to enter the setup GUI where the average group size can be changed using (the default value is 5).
• STEP 2: Press to complete setup and return to the main menu.
• STEP 3: Press to return to the average measuring GUI (As shown in Figure 4-6);
• STEP 4: Ensuring good coupling, measure the thickness of point N. Then lift the probe and measure the thickness of the next point and repeat until all data points are measured. Each measurement reading will be displayed in the center of the screen as they are made, and the number of the current measurement being made is displayed after
  • ‘NOW:’ in the bottom-left of the screen. After completing all measurements, the average thickness will be displayed in the center of the screen.

STD (STANDARD MEASUREMENT MODE)
Standard mode is a basic measurement mode that can be used to measure the thickness of a material. Select STD using to complete setup. Press return to the measuring GUI (As shown in Figure 4-7);

RESL (DISPLAY RESOLUTION)

The display resolution (the number of digits shown to the right of the decimal point of a reading) can be changed using this setting. This may be useful in some applications where the extra precision of the last digit is not required or where extremely rough outside or inside surfaces make the last digit unreliable. There are two resolutions to select from: 0.01mm and 0.1mm. To change the display resolution, select RES in the main menu using Then select 0.01 or 0.1 using to complete the display resolution setup and to return to the main menu.
Note: If the gauge is turned off before the key is pressed, the display resolution will retain the previous resolution.

RATE (MEASUREMENT RATE)
This option allows the measurement rate of the gauge to be changed (this affects the power of the gauge). The measurement rate can be changed from 2 times per second to 20 times per second. Select RATE in the main menu and press The current frequency will be displayed, and this can be adjusted usin to complete the measuri ng frequency setup and return to the menu.
Note: If the gauge is turned off before the is pressed the measurement rate will retain the previous current value.
Note: The battery drain rate is increased when the measurement rate is increased.

AUTO OFF

The
gauge is programmed to automatically shut down after 3 minutes without operation. For conv enience, this can be changed to suit the user’s needs. Select AUTO OFF in the main menu and adjust the shut down time (in minutes) using. The user can also press to select NOT AUTO SHUT (no automatic shut down).

RESET
To restore the gauge to it s default setup, press and hold both keys and then press to power on the gauge . This may be useful for new operators whilst they become familiar with the se tup of individual features as described previously. This may also be useful for experienced opera tors as an efficient short cut to a known configuration. You can also restore the gauge to its default setup by selecting
RESET in the main menu using

CONTR (DYNAMIC)

To adjust dynamic contrast, select CONTR in the main menu usi ng and adjust the dynamic contrast to your requirements using

• Default: 4
• Range: 1 32
• Step size: 1

LANGUAGE

You can change the operating lan guage of the gauge . Press to enter the main menu, select LANGUAGE by to proceed, and select either ENGLISH or CHINESE using

Note: If the gauge is turned off before the key is pressed, the language will not be changed but instead wi ll retain the previous current units.

PROBE ZERO CAL

Whenever the probe is changed, it is recommended to do a probe zero calibration to improve measuring accuracy and to ensure proper probe functionality. This can be completed by selecting AUTO TEST PRB from the main menu using
Note: Keep the probe clean before calibrating, and w ipe any couplant from the probe.
MANU SELECT PRB (MANUALLY SELECT

To manually select a probe, select MANU SELECT PRB from the main menu using to complete.
Note: Keep the probe clean before calibrating, and wipe any coup lant from the probe.

OUND (SOUND SET UP

Sound in the gauge can be switched on or off by selecting SND SET from the main menu using

ROTATE (SCREEN

For inverted inspections, the display can be rotated 180°. To do this, sel ect ROTATE from the main menu using

(ONE POINT CALIBRATION)

For a one point calibration of an unknown material velocity (using one thi ck test block), select 1 POINT in the main menu using . The procedure for one- point calibration can be found in Section 3.2.1.

(TWO POINT CALIBRATION)

For a two point calibration of an unknown material velocity (using one thin and on e thick test block), select 2 POINT in the main menu using . The procedure for two-point calibration can be found in Section 3.2.2.

VELOCITY PRESET (VELOCITY TABLE)
If the sound velocity of a material is known, calibration is not necessary and the velocity may be entered directly as a known velocity as discussed in Section 3.2.3 (the initial setup of the gauge is 5900m/s). The gauge is also pre installed with 9 different material velocit ies that can be found in the velocity table. This can be accessed by selecting V IN in the main menu using , and pressing to enter the VEL TABLE, where you can select the appropriate velocity using and
Note: If the gauge is turned off before is pressed, the velocity will not be updated to the new value but instead will retain the previous current value.

BACK LIGHT

The display backlight feature internally illuminates the liquid crystal display with a bright uniform light. This allows the display (which has excellent visibility in normal to hi gh ambient light conditions) to be viewed in low to zero ambient light conditions. To adjust back light settings, select BACK LIGHT using , and select AUTO , ON or OFF using Additionally , you can press to turn the backlight on or off.

• AUTO: the light turns on and off
• ON: the light is always on.
• OFF: the light is alwa ys off.

Press to complete the backlight setup and return to the main menu.
Note: If the gauge is turned off before is pressed at last, the backlight mode will not be updated but instead will retain the previous current mode.

DIM PIPE WALL MEASUREME NT MODE

If the thickness of a pipe wall is to be measured , please select this measurement mode from the main menu.

APPLICATION NOTES

FACTORS AFFECTING PERFORMANCE AND ACCURACY SURFACE CONDITION

Loose or flaking rust, corrosion or dirt on the outside surface of a test piece may interfere with the coupling of sound energy from the probe into the test material. Thus, any loose debris of this sort should be cleaned from the specimen with a wire brush or file before measurements are attempted. Generally, it is possible to make measurements through thin layers of rust, as long as the rust is smooth and well bonded to the metal below. However, very rough cast or corroded surfaces may have to be filed or sanded smooth in order to ensure proper sound coupling. It may also be necessary to remove paint if it has been applied in thick coats or if it is flaking off the metal. Severe pitting on the outside surf ace of a pipe or tank can be a problem. On some rough surfaces, using gel or grease rather tha n a liquid couplant can help transmit sound energy more effectively into the test material. In extreme cases, it may be necessary to file or grind the surface sufficiently flat to permit good contact with the face of the probe. In applications where deep pitting occurs on the outside of a pipe or tank it may be necessary to measure the remaining metal thickness from the base of the pit to the inside wall. The conventional technique is to measure the un pitted metal thickness ultrasonically, measure the pit depth mechanically, and subtract the pit depth from the measured wall thickness. Alternately, one can file or grind the surface down to the base of the pits and measure normally. As with any difficult application, experimentation with actual product samples is the best way to determine the limits of a particular gauge /probe combination on a given

PROBE POSITIONING/ALIGNMENT For proper sound coupling, firmly press the probe against the test surface. On small diameter cylindrical surfaces such as pipes, hold the probe so that the sound barrier material visible on the probe face is aligned perpendicular to the center axis of the pipe (refer to Figure 6 .1). Fig. 5 1: Correct positioning of probe against a small diameter cylindrical surface I  t is possible that on some severely corroded or pitted materials there will be spots where readings cannot be obtained. This can happen when the inside surface of the material is so irregular that the sound energy  is scattered rather than reflected back to the probe. The lack of a reading may also indicate a thickness measurement outside the suitable range for the probe and gauge. Generally, however, an inability t o obtain a valid thickness reading at a particular point on a test specimen is a sign of a seriously degraded wall which may warrant investigation by other means.

CALIBRATION
The accuracy of measurements is only as good as the accuracy and care with which the gauge has been calibrated. It is essential that velocity and zero calibrations zero calibration is done automatically in this type of gauge) be performed whenever the test material or probe is changed. Periodic checks with samples of known thick nesses are recommended to verify that the gauge is operating properly.

TAPERING & ECCENTRI CITY
If the contact surface and the back surface are tapered or eccentric with respect to each other, the return echo again becomes distorted and the accuracy of measurement is diminished.

ACOUSTIC PROPERTIES OF THE MATERIAL
There are several conditions found in engineering materials that can severely limit the accuracy and thickness range that can be measured.
Sound Scattering:
In some materials notably c ertain types of cast stainless steel, cast irons and composites the sound energy is scattered from individual crystallites in the casting or from dissimilar materials within the composite. This effect reduces the ability to discriminate a valid return ec ho from the back side of the material and limits the ability to gauge the thickness of the material ultrasonically.
Velocity Variations:
A number of materials exhibit significant variations in sound velocity from point to point within the material. Certain types of cast stainless steels and brass exhibit this effect due to a relatively large grain s ize and the anisotropy of sound velocity with respect to grain orientation. Other materials show a rapid change in sound velocity with temperature. This is characteristic of plastic materials where temperature must be controlled in order to obtain maximum precision in the measurement.
Sound Attenuation or Absorption:
In many organic materials, such as low density plastics and rubber, sound is attenuated very rapid ly at the frequencies used in normal ultrasonic thickness gauging. Therefore, the maximum thick ness that can be measured in these materials is often limited by sound attenuation.

PROBE SELECTION

• For any ultrasonic measurement system (probe and gauge to gether) there will be a minimum material thickness below which valid measurements are not be po ssible. Normally this minimum range will be  specified in the manufacturer’s literature. Generally, however, as probe frequency increases, the minimum measurable thickness decreases.
• In corrosion applications, where minimum remaining wall thickness is normal ly the parameter to be measured, it is particularly important to be aware of the specified range of the probe being used. If a measurement system is used to mea sure a test piece that is below its designed minimum range, the gauge may detect invalid echoes and display an incorrectly high thickness reading.
• Table 1 3 lists the approximate minimum measurable thicknesses in steel for the standard and optional probes used with the gauge . Note that these figures are approximate; the exact measurable minimum in a given application depends on material velocity, surface conditions, temperature and geometry. It is recommended that the measurable minimum be determined exper imentally by the user.
• In selecting a probe for a corrosion application, it is also necessary to consider the temperature of the material to be measured. Not all probes are designed for high temperature measurements. Table 1 3 also lists recommended tempe rature ranges for the probes used with the gauge . For other consult the manufacturer’s ca talogue or data sheets. Using a probe on materials that have temperatures beyond the specified range can damage or destroy the probe.

HIGH TEMPERATURE MEASUREMENTS

• Corrosion measurements at elevated temperatures require special consideration. Please keep in mind the following:
• Be sure that the surface temperature of the test piece does not exceed the maximum specified temperature for the probe and couplant that you are using. Some probes are designed for room temperature measurements only.
• Use a couplant rated for the temperature at which you will be working. All high temperature couplants will boil off at some temperature, leaving a hard residue that is not able to transmit sound energy.
• Panametrics-NDTTM Couplant E (Ultratherm) can be used at temperatures up to 1000°F/540°C, although it will similarly boil as the upper limit is reached. Maximum recommended temperatures for Panametrics couplants are in the table below:

• Make measurements quickly and allow the probe body to cool between reading s . High temperature probes have delay lines made of thermally tolerant material, but with continuous exposure to very high temperatures the inside of the probe will heat to a point where the probe may be permanently damaged.
• Remember that bo th material sound velocity and probe zero offset will change with temperature. For maximum accuracy at high temperatures, perform a velocity calibration using a section of the test bar of known thickness heated to the temperature at which measurements are to be taken. The gauge has a semiautomatic zero function that can be employed to adjust zero set ting at high temperatures. See Section 3 for details.
• Note that a corrosion gauge is not designed for flaw or crack detection, and cannot be relied upon to detect material discontinuities. A proper evaluation of material discontinuities requires an ultrasonic flaw detector such as the QingCheng SUFD2 used by a properly trained operator.
• In general, any unexplained readings by a corrosion gauge merit further testing with a flaw detector.
• For further information on the use of dual element probes, or for information on any aspect of ultrasonic testing, please contact us.

MAINTENANCE AND TROUBLE SHOOTING

ROUTINE CARE AND MAINTENANCE
The case of the gauge is sealed to prevent intrusion of environmental liquids and dust. However, it is not completely waterproof and thus should never be immersed in any fluid. To clean the case, keypad and display window, use a damp cloth (and mild detergent if necessary). Do not use strong solvents or abrasives.

PROBES

• To ensure the longest lifespans for your ultrasonic probes, please pay attention to the following: The cables can be damaged by cutting, pinching, or pulling on them. Take care to prevent any mechanical damage to the cables. Never leave a probe where a heavy object can be placed on the cable. Never remove a probe from the gauge by pulling on the cable. Pull on the molded connector housing only. Never tie a knot in a probe cable.
• Do not twist or pull the cable at the point where it connects to the probe. These precautions are particularly important for all probes other than the models which have field-replaceable cables. For repair of damaged probes, please return them to the QingCheng Customer Service Department.
• Probe performance will be degraded by excessive wear at the tip. To minimize wear, do not scrape or drag the probe across rough surfaces. When a probe tip becomes too rough, concave, or otherwise non-flat, operation may become erratic or impossible. Although some wear is normal in corrosion-gauging applications, severe wear will reduce the probe life. A probe resurfacing procedure can be performed to improve performance of worn probes. Please contact us for details.

OTHER ERROR OR PROBLEM INDICATIONS TURN ON AND LOW BATTERY PROBLEMS
If the gauge turns off immediately after power-on, or if it does not turn on at all, then the battery is probably completely discharged and should be replaced. If the unit will still not turn on after replacing the battery, there may be a component failure within the gauge and it should be serviced.
COUPLING PROBLEMS
If no thickness measurement is displayed when the probe is coupled to a test material, make sure that the probe is plugged in properly (see Section 2.1). If there is still no measurement display, the probe may be defective – try another one if possible, or try a different cable if it is the type of probe that uses replaceable cables
IDENTIFY PROBE PROBLEM
If the gauge doesn’t register the probe being plugged in, please first ensure that the probe is well connected to the gauge . If the gauge still doesn’t register the probe, please exchange the plugs and make sure they are well connected to the gauge . If the problem select AUTO TEST PRB from the main menu using , and select the appropriate probe.

MEASUREMENT PROBLEMS

If measurements cannot be made, there is either a problem with the probe, the pulser/receiver assembly, or there is not a large enough echo being returned from the far wall of the material. In order to further diagnose the problem, please perform the followi ng procedure:

• STEP 1: Wipe off any couplant from the probe and do a VELOCITY CAL IBARATION . If a number is displayed alongside the VELOCTIY CAL IBARATION flag, both the probe and pulser/receiver assembly are working (proceed to step 2). If otherwise, proceed to step 6.
• STEP 2: Make sure sufficient couplant is applied, especially on rough or curved surfaces. Proceed to step 3.
• STEP 3: Try the same probe on a smooth, flat surfaced test sample.
• STEP 4: If steps 1, 2 and 3 all succeed but measurements still cann ot be made, try a different type of probe which has greater sensitivity to the thickness range in whic h you are working.
• STEP 5: If another probe of the same type is available, use it to make measurements and repeat step 1. If this works, then the origina l probe is likely to be defective. Otherwise, the pulser/receiver assembly is probably defective.
• STEP 6: If the above tests indicate that there is a problem with the gauge or probe, then the unit(s) may be returned to us for repair or replacement. If the a bove tests indicate that the gauge and probe are working properly, then the test material itself is l ikely to be defective for the following reasons:
  • Extreme near side or far side surface r oughness.
  • Extremely high sound attenuation or scattering due to gra ininess, inclusions, voids or other material properties.
  • Extreme non parallelism.
  • Excessively sharp c urvature.

APPENDIX

SOUND VELOCITIES
The following table provides a list of the ultrasonic velocities in a variety of common materials. It is provided only as a guide as the actual velocities in these materials may vary significantly due to numerous factors, such as composition, preferred crystallographic orientation, porosity, and temperature. Therefore, for maximum accuracy, it is recommended that the sound velocity be experimentally determined by first testing a sample of the material. Sound Velocities of Various Materials Lonaitudinal Wave Velocitv|
Sound Velocities of Various Materials Longitudinal Wave Velocity

CONTACT

• Qingcheng AE Institute (Guangzhou) Ltd
• www.aendt.com.
• Tel: 86 20 32290092
• [email protected].

References

• Find Your Dream Tech Job with NDT | Boston's #1 Tech Recruiter
• Acoustic Emission, Vibration Monitoring and Condition Monitoring Systems in NDT industry | QAWRUMS Ltd.

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