CTG Manual
Contents
1. click on the spaces as delimiters box or otherwise tell the spreadsheet program to split up the data based on the location of spaces One typical application of the spreadsheet data is to plot the thickness versus test point If the tests were performed along a line of evenly spaced points the resulting plot will be a profile of concrete thickness along a line across the slab or wall If multiple lines are tested the data can be imported into a program such as Surfer to create a 2 D plot of thickness across an area A typical plot from a spreadsheet showing the thickness profile of a slab on grade is presented This is a plot of tests conducted at 1 foot intervals across a 60 foot slab and shows the typical variation of slab thickness that can occur A data set such as this one can be collected in 10 minutes or less on a clear floor with no obstructions to be moved DOWNLOAD TROUBLESHOOTING If problems are experienced in downloading the most likely cause is a problem in the serial connection between the computer and the CTG unit If the download software runs but no data appears to be downloading the counter does not increment check the following 1 Be sure the CTG unit is in DOWNLOAD mode as described in the download procedure above prior to clicking on Download CTG 2 Be sure that there are saved records in the CTG Number of saved records is greater than 0 Page 14 3 Check the connection between the CTG2. start again by pressing 2 then 4 then 4 when ready After clicking the Download CTG button the download process will begin For CTG 1T units the downloading will be fast as only the results data is being sent Downloading of 100 records should only take 5 10 seconds For CTG 1TF units the downloading requires just under 1 second per record to complete due to the additional data being sent Thus 100 records will take about 1 5 minutes to download At the end of a successful download the status window will show the total number of records downloaded Click on OK to exit At this point the user of a CTG 1TF unit can use the TFS Page 13 software to analyze the data This is discussed in the TFS user manual Users of CTG 1T and CTG 1TF units can use a spreadsheet program to look at the downloaded data results file This file is discussed below CTG RESULTS FILE The CTG results file is an ASCII file with data arranged in columns The column format is as follows 1 Test Number 2 Measured Thickness in or cm 3 Velocity in ft s or m s 4 Max Thick Value in or cm 5 Q Value 1 9 6 Units of Test O Metric 1 English 7 Date of Test MM DD YY 8 Time of Test HH MM SS The columns of information are separated by spaces so CONCRETE SLAB THICKNESS Series1 Thickness inches w o 20 40 60 Distance feet when importing the data into a spreadsheet be sure to
3. this type of response will be particularly likely when testing on a thin section with the unit set to THICK mode To eliminate the possibility of these false readings the CTG requires the user to input a design thickness from which the operating mode and peak picking algorithm are selected and the Max Thick value computed This will limit the maximum thickness range of the CTG to 33 greater than the entered design thickness Note that if the unit is then used to test thicker concrete the design thickness value will have to be changed by reentering a new Max Thick value or by cycling the unit off and then on and entering a new design thickness Display Messages Several different messages may be displayed instead of the thickness after a test if the test does not yield clear results If the CTG does not receive good data with a clear echo peak from the concrete thickness the unit will not give a thickness reading and will instead give a message to the user indicating why a reading was not obtained Page d A message of No Signal Retest Press any Key indicates that the signal level seen by the transducer was insufficient This will typically happen if the test is done with the test head in air or otherwise not in good contact with a smooth concrete surface For THIN mode this can also result from the anvil not being in direct contact with the concrete surface either because it is over a hole or depression or if the solenoid is
4. with a valid velocity entered will save the velocity and return to the main menu ready to test If no location is available on the test member with a known thickness then the accuracy of the thickness readings can still be improved over the default accuracy by inputting a typical value from the table below based on the estimated strength of the concrete Typical velocity ranges for normal concrete designs are as follows 14 20MPa 3353m s 20 31MPa 3657 6m s default value 31 38MPa 3962m s 38 48MPa 4267m s Note that these values are general guidelines only and should only be used if a direct calibration cannot be done Using these values should improve the accuracy of the thickness measurements but will not result in accuracies equal to those from a direct calibration Please note that while the CTG can be used to measure velocity of an unknown concrete material use of these measured velocities to back calculate strength Such as from the table above is NOT recommended and will not necessarily be accurate without correlation testing to actual strength values for a particular mix design GRAPHICAL SPECTRAL DISPLAY The CTG includes a graphical display which presents the frequency spectrum of the data collected for each test although the spectrum plot includes a scale on the bottom which shows approximate thickness rather than frequency to simplify the data analysis The automatically picked thickness echo peak is noted on the d
5. 2 displayed Max Thick value unless the Max Thick value is changed in the Calibrate Menu discussed below The alternative way to change the thickness range of the unit such as changing to a different slab or wall thickness is to cycle the power off and then back on and enter the new design thickness Note that in THICK mode the minimum thickness is about 30cm Thus if testing thinner members lt 30cm in THICK mode the results will not be correct After the expected thickness is entered the main menu Test Cal Data Resolution or Mode will appear To perform a simple test using the built in default concrete properties values simply press the test head against the concrete and press any RED key 1 3 or 0 or the red FIRE button on the side In THIN mode the impactor on the test head should click one to four times and the screen will clear In THICK mode the screen will display Strike Surface At this time impact the surface next to the test head with a small hammer Strike the surface within about 15cm of the test head The selection of hammers is discussed in a section below For either mode if valid data was obtained in a few seconds the thickness will appear in inches or centimeters depending on the English Metric units switch along with a spectral display of the data with the picked peak marked The marked peak is the frequency peak used to compute the displayed thickness At the lower
6. amplitudes 7 When moving the test head to a new location take care not to drag the transducer head the orange urethane button on the bottom of the large round cylinder across the concrete as this will cause excessive wear n the transducer 8 While the test head will operate properly on wet concrete or even through a film of water do not submerge the test head If the test head falls into water disconnect the cable clean off any mud or dirt and allow it to dry out as soon as possible 9 The keypad is designed for finger operation Do not operate the keypad with a sharp object such as a pencil end as this may pierce the keypad cover and damage it 10 When placing the test head on a surface place the rear feet down first and then rotate the unit down into position This will ensure proper contact between the transducer tip and the test surface CTG 1T F SPECIAL FEATURES The CTG 1T and CTG 1TF are versions of the CTG which allow the user to output a table of test results through the serial port to a PC for subsequent storage manipulation and display In addition the CTG 1TF also downloads the saved time domain data traces collected for each saved test This time domain data can then be analyzed by the TFS signal analysis software package One feature common to both the CTG 1T and CTG 1TF is the inclusion of a time date clock which can be set by the user The time and date of each test is saved along with each saved data set f
7. left side of the screen the option to EXIT or SAVE is presented Pressing 1 EXIT will clear the last reading and display the main menu again Pressing 2 SAVE will save the data in memory including the displayed spectrum and display to the user the current record number the data was saved under The unit is capable of storing up to 300 records after which a Memory Full message will appear and no more data will be saved To save more records the memory must be first cleared See section on Data Recall menu The unit is now ready for the next test Note that multiple impacts in THIN mode after a FIRE command are caused by automatic gain adjustment and re firing of the unit if the signal received was too strong or too weak in a given test There is no gaining in the THICK mode as the unit is fixed at the lowest gain setting due to the higher energy typically produced by external hammers THICK Mode Hammer Selection When testing in THICK mode the selection of the proper hammer is important in obtaining the best quality data For tests on walls expected to be between 60 150cm in thickness a 1 2 kg steel hammer will be the best choice For thicker structures use of a 1 5 kg or larger hammer will resoit fElearer data Units Backlight Onerational Controls Page 3 Backlight The CTG has a built in backlight for the display to allow operation in low light conditions Simply press in the Backlight switch to
8. picked by simply re setting the Max Thick value to a lower value From the spectra shown above it is clear that there are no other significant peaks present beyond the very low frequency peaks at the left end of the spectra so any Max Thick value in the range of 5 to 8 inches would be usable A re test at the same location after setting the Max Thick value to 6 inches is presented below As can be seen this pectra does not include the low frequency deep data and the automatic pick is correct at 3 7 inches CARE AND MAINTENANCE The CTG is a rugged unit designed for construction site use but it is not indestructible Certain precautions should be taken to ensure the reliable operation of the unit 1 The CTG should not be exposed to direct rain or other moisture 2 Take care not to drop the CTG or the test head as damage may result 3 Do not pick up the CTG or the test head by the cable as the cable and connector are not designed for this type of stress 4 The display screen can be damaged by impacts excessive pressure or sharp objects 5 Do not leave the power switch in the ON position OPESe 9 the batteries have been discharged unless the unit Is being used with the external power supply charger attached 6 The test head should be kept clean and free of mud and dirt as mud can interfere with the operation of the solenoid impactor and small rocks or other objects on the sensor face can result in poor data or low signal
9. 60302 press ENT to enter the date and move to the time set Enter the time in the format HHMM where HH is the current hour in 24 hour format and MM is the current minute Then press ENT to enter the time and return to the main menu DATA SAVING AND DOWNLOADING For the CTG 1T and CTG 1TF the test results and test time data are saved automatically each time the user elects to save a record from the test results display screen In addition for the CTG 1TF the time domain waveform data for the current test is also saved at the same time The test result which are saved by the unit for each test include the test number displayed upon saving the measure thickness in inches or centimeters depending on units switch setting the Q value the units 1 for English 0 for metric the Max Thick setting the velocity at the time of test and the time and date of the test These parameters are downloaded in ASCII format into a tabular format file which can be easily read in by Excel or other spreadsheet programs To download the data the user must first install and run the CTG 1T F download software on a Windows PC WIN 95 98 2000 with a free serial COM port The software is capable of using COM1 COM4 for download To install the download software first insert the software CD in to a CD drive Using Explorer or other file display software open the CD directory and double click execute the SETUP file Follow the instructions on scre
10. Concrete Thickness Gauge Quick Start Guide _ Connect the test head to the hand held reader 2 Turn Power on by depressing power switch on top of reader 3 Enter guess for design thickness of concrete element in centimetres The equipment will automatically add 33 to this to ensure the correct thickness is found 4 Note if the design thickness is more than 60cm the thick mode of operation will be automatically selected This requires a secondary impact device ie hammer to be used Refer to the users manual for details 5 A pulse velocity must be set for accurate thickness readings Select option 2 Cal Data in the menu 6 Option 2 from this menu an insitu calibration Find some concrete of known thickness Enter the thickness in centimetres Press 1 to fire the striker A pulse velocity should be returned If not try again making sure the concrete surface is reasonably smooth 7 Option 1 from this menu allows the velocity to be set by the user This can be estimated with the chart in the Users Manual page 8 using an estimation of the concrete strength 8 Once velocity it will return to the main menu Thickness testing can begin 9 Hold the test head on the concrete where a thickness is desired Press 1 to do the test After a second or two the thickness should be displayed 10 This can be stored or dismissed If any error message is displayed refer to the manual for meaning 11 Install the software include
11. Note that the CTG does not require a strong hard hot to collect good quality data A light strike with the hammer allowed to rebound off of surface is usually the best A message of No Echo Retest Q 0 any key indicates that the signal amplitude was good but that no clear echo peaks were found in the record This can happen if the tested member is very thick if the concrete is internally honeycombed or has multiple fractures or if the back side is very uneven such that no single thickness is seen This message can also happen if the design thickness value is set too low for the concrete thickness being tested Note that the IE method relies on seeing reflections from changes in sound wave velocities to measure thickness If the concrete is on top of a similar stiff material such as rock or a cementitious base course no echos may result and this message will appear This message can also appear in THIN mode if the batteries are very low low battery light on or flashes during impacts and the impact is therefore too weak to produce a strong signal A message of Adjust Sol UP Press any key THIN mode only indicates that the solenoid may be too close to the anvil on the concrete surface This will happen if the anvil is resting on a high spot under the impactor or if the solenoid needs to be adjusted up in the frame K the message repeats at several locations adjust the solenoid up by 2 3 mm and repeat the test Th
12. activate Note that the continuous use of the backlight will reduce the battery life by a few hours English Metric Units Selection The CTG can operate with either English units or Metric units The units are selected by the push on pushoff button at the top of the CTG labeled English Metric For English units the thicknesses are displayed in inches in and velocities in feet per second ft s For Metric units the thicknesses are displayed in centimeters cm and velocities in meters per second m s Changing the units switch with a thickness or velocity displayed will immediately recomputed the thickness or velocity in the new units and re display the new reading Changing the units will also re compute the current velocity for thickness calculations and Max Thick value to the new units selected OPERATION NOTES AND HINTS Max Thickness The CTG with the THIN THICK software will work on concrete walls and slabs with thicknesses ranging from approximately 4cm to over 1 8m under ideal conditions In THIN mode the most reliable readings from the unit will result from tests in the 5 25cm range Slabs which are in the thinner end of the operating range less than 10cm will sometimes give false readings which are much too thick such as 25 30cm from a 4 5cm thick slab if the design thickness and thus Max Thick is set high such as 25 30cm This is normal and is due to additional resonances present in a thinner slab Note that
13. ase note that for the CTG 1TF this manual only includes instructions on collecting and downloading the data Instructions on the use of the TFS software for full data analysis on the users PC are included in a separate manual for the TFS software Page 1 BASIC OPERATION Hardware Connection The CTG system consists of several basic parts the CTG main body with integral cable the test head which includes the sensor solenoid impactor for THIN mode tests and a selection of external hammers for THICK mode tests Hardware connection consists of connecting the connector on the end of the integral cable to the test head NOTE Do note allow dirt or moisture to enter the ends of the test head or cable connectors as this may interfere with the connection and or operation of the unit To connect the test head butt the two connectors together and rotate the cable connector until it partially engages Then rotate the lock ring of the cable connector clockwise to screw it down until it locks into place on the test head The connector should engage fully onto the test head connector and click into place during the locking process Test Head CTG Operation Once the test head is connected to the cable _the CTG may be turned on by pushing the push on pus switch The CTG model CTG 1 CTG 1T CTG the version number of the software v momentarily followed by a display of the records currently saved in memory The p ATE then ask the user f
14. d not be done in THIN mode on very thick over 25 cm or very thin under 8 cm members for the best reliability When testing in THICK mode we recommend a thickness range of 60 150cm for the best calibration data In addition calibration should be done on a smooth clear surface with a flat backside to obtain the clearest possible data Once a valid velocity obtained the unit will now use this velocity for all subsequent tests until it is turned off or the unit is re calibrated If large amounts of testing are anticipated for a particular type of concrete the user should write down the velocity displayed to allow the direct entry of the velocity in the future after the unit has been turned off and the velocity re sets to the 7 default using the procedure described in the next paragraph The second calibration method is the direct entry of the velocity of the concrete in either ft s or m s This method of calibration can be used if a velocity has already been determined for a particular concrete type from a previous thickness based calibration for instance or if the approximate velocity is known based Page 7 on experience with similar concrete batches or the general mix design To enter the velocity directly from the main menu press 2 cal data then 2 Velocity Input the velocity in ft s or m s as requested on the display Note that the velocity must be in the range of 1 500 to 7 600 m s to be accepted Pressing ENT
15. d with the equipment and use the CTG download icon to start the download When downloading ensure that the option 2 Cal Data then 4 Download recall is chosen on the hand held unit 12 The resulting dat file stored in the created CTG folder can be viewed using Excel or Notepad See page 11 14 for detailed description Please refer to the user manual for more detailed instructions if any difficulty is experienced IE Theory The CTG operates on the principles of the Impact Echo IE test method This method was developed specifically for use on concrete to allow single sided echo testing for thickness measurements and flaw detection The IE test method uses a sensor to measure and record the waveform resulting from an impact to the surface adjacent to the sensor This time domain data time versus amplitude includes energy from the initial impact as well as energy from echoes of the initial impact which have traveled through the concrete and echoed off of the back side or off of any shallow cracks parallel to the test surface By performing a Fast Fourier Transform FFT on the data converting it to frequency versus amplitude the echoes from the backside become clear and easy to see appearing as amplitude peaks in the frequency versus amplitude spectrum plot It is important to remember that each specific frequency in the spectral display corresponds to a specific thickness or depth Pulse Oscillascope Perform FFT Transmitt
16. e Q value X message where the X is a number 0 9 is an indication of the sharpness of the echo peak For tests with a valid thickness higher Q values are indicative of a smooth even back side Concrete slabs on grade or walls with uneven back sides will generally result in a lower Q value Note that a low Q does not necessarily indicate a poor reading but may indicate that the actual concrete thickness in the area of the test location varies over a range due to uneven concrete Tests on samples such as standard concrete cylinders will normally give the highest Q values 9 typically due to the sharp resonance of the cylindrical shape The Q value can be correlated with the spectrum on the screen with sharper spectral peaks resulting in higher Q values High Low Resolution Mode The CTG offers two selectable thickness resolution modes The default mode is approximately 2 5 of the thickness reading while the high resolution mode is approximately 1 of the thickness reading Selecting the resolution mode is done by pressing either 7 low resolution or 9 high resolution when the main menu is displayed The option displayed at any given time will be the option that is currently NOT selected as this allows the user to change options if desired The screen will clear momentarily as the new resolution mode is stored and then the main menu will reappear Note that the computation of the thickness after each test will take ab
17. en to install the software and select the location for the shortcut on the START menu If a single computer is to be used often for downloading it may be useful to create a shortcut on the desktop to the download software as well Please note for certain computers there have been reports of errors in registering certain files during loading If this occurs simply choose Ignore and continue on The software in all cases has loaded correctly After the completion of software loading the normal location for the shortcut is under the START menu PROGRAMS CTG 1TF DOWNLOAD Open this menu item to access the download software shortcut Drag this shortcut out into the desktop to create an easily accessible icon Executing the download software will open up the main download dialog box as pictured below The box SNOW the pre selected default file names as well as the various options for use DOWNLOAD DIALOG BOX FUNCTIONS Results File Name Display and Selection The download software allows the user to select a file name and location for the downloaded ASCII results data Select Results File button and shows the currently selected results file name and location This is the only file name option applicable to the CTG 1T systems Please note that if an existing file name and directory is selected as the download target or if the default file name and directory is used all the time the download software WILL OVERWRITE any data curre
18. er Receiver A The simple formula T C 2F is used to find the thickness of the concrete where T Thickness C the velocity of the waveform through the concrete and F is the frequency found by performing the FFT It is important to remember that for this relationship to hold the concrete must act as a plate whereby the width and breadth of the concrete is at least 3 times the thickness CTG Concrete Thickness Gauge User Manual The CTG series of instruments are powerful hand held devices designed primarily to measure the thickness of thin concrete slabs and walls in the range of approximately 4cm out to about 2 4m without the need for drilling coring or other means and with only access to one side of the member required In addition the CTG 1T system allows saving and downloading of the test results into a spreadsheet for profile generation etc while the CTG 1TF system also allows downloading of saved waveforms into a powerful analysis software package that lets the user perform additional analyses of the data This additional analysis capability turns the CTG 1TF into a fully functional Impact Echo IE based flaw detection system capable of analyzing echoes from multiple cracks and other flaws The CTG units feature a graphical display of the received signal spectrum which can be saved and recalled on the unit which allows visual indication of data quality easy differentiation of bad data and even the location of part
19. f the concrete Lower strength mixes typically have velocities in the lower range while high strength mixes have higher velocities The default velocity is 3 657 m s which is a typical value found in normal slabs and walls with 20 27 5MPa concrete mixes Using this velocity with no additional calibration should give thicknesses within 10 or less of the actual value for most concrete structures To increase the accuracy the CTG offers two easy ways to calibrate the unit to the specific concrete being tested The first calibration method requires a test location with a known thickness This can be on any testable part of the member being tested or on a structure or test cylinder made from similar concrete From the main menu press 2 Cal and then 1 Thickness Next enter the thickness in the units requested depending on the current Units switch setting either inches or centimeters at the calibration location and then press ENT Next press the test head onto the surface at the known thickness location and perform a test press a red key or the FIRE button If valid data is obtained the CTG will display the measured velocity at the test location Be sure that the velocity displayed is reasonable for the material being tested i e in the normal concrete velocity range for concrete tests If the velocity is not as expected repeat the test or move to a different location Note that a thickness based calibration shoul
20. ial cracking damage This line of instruments can also be used to determine relative concrete quality by measuring concrete compression wave velocity for test cylinders and other samples with known thicknesses The device can also be used for thickness measurements of many materials other than concrete such as plastics stone etc depending on the properties and internal structure of the material being tested The CTG line includes the capability for measuring in two ranges The THIN range uses the internal solenoid striking as an impact source and is used to measure thicknesses from 4 to about 50cm The THICK range is used for thicknesses greater than 50cm and requires the use of an external hammer for greater low frequency energy to generate the impact for echo frequency measurements The range setting of the unit is automatically set upon start up based on the design thickness entered by the user or can be manually selected during use from the main menu The CTG lines are rugged battery powered units designed for easy fast and reliable operation by anyone with no special training required for basic operation This operation manual begins with a description of the hardware and simplified operating instructions for all three models continues on to a more detailed explanation of the various features and functions available and then includes sections specific to the operations of the special features of the CTG 1T and CTG 1TF Ple
21. ion OK and Cancel Buttons Both of these buttons can be used to exit the program At this time there is no difference in function between them DOWNLOADING PROCEDURE The basic procedure for downloading data is the same for both the CTG 1T and CTG 1TF with the exception that the CTG 1TF requires the selection of an additional file base name for the downloaded data files The step by step procedure is as follows 1 Connect the CTG to a PC serial port via the download cable supplied with the unit 2 Start the download software 3 Select the correct COM port 4 Select the desired file name and directory for the ASCII results data file 5 Set the file download base name and directory for time domain file downloads CTG 1TF only 6 Turn on the CTG unit enter a dummy design thickness of any valid value 9 inches etc 7 On the CTG press 2 to enter the cal data menu then press 4 to select Download Recall then press 4 again to select Download The number of saved results will appear on the screen and the CTG is now in DOWNLOAD mode 8 Click on the Download CTG button on the software Note you have about 25 seconds to click on the Download CTG button after the selection of Download on the CTG Download Recall menu while the CTG is displaying the number of saved records If no action is taken within 25 seconds the CTG will exit DOWNLOAD mode and will go back to the main menu To download data simply
22. isplay with a small cross This peak is the one used to compute the measured thickness which is numerically displayed on the left side of the screen i e T 7 9 in The sharpness of this peak is reflected in the Q value displayed right under the thickness value Note that the thickness range displayed is different for THIN and THICK modes This is due to the different sample rates for the two modes which results in different frequency spectral ranges All required conversions are taken care of by the internal software during mode switching 1 3in 3 7in CTG 1T Display Test on a 3 7 inch slab with 25 inch Max Thick There are several advantages to having the complete spectral display rather than just the picked thickness value The most important is that the validity of the Page 8 picked peak can be checked For cases such as very thin concrete there are often several peaks present with a high frequency shallow peak from the actual thickness echoes and one or more low frequency deep peaks resulting from structural resonances A typical example is presented below of a test on a thin 3 7 inch concrete slab on grade but with the Max Thick value set to 24 inches The CTG automatically picked the low frequency structural resonance peak at 21 3 inches as the thickness peak but there is a clear thickness echo peak present at 3 7 inches Correct Thickness of 3 7in The correct shallow thickness peak can be automatically
23. nstalled or turned on Note that most motherboards allow the activation or deactivation of the COM ports in the CMOS setup mode If one or more serial ports have been turned off they will not be usable until turned on again If more than one valid COM port is shown on the screen select the port that will be used for the download Note that one of the most common problems in downloading data is the selection of a different COM port in the software than the one to which the download cable is connected Clear CTG The Clear CTG button is used to ERASE all data currently stored in the CTG if it is in DOWNLOAD mode Pressing this button will bring up a confirmation message asking the user to click one more time and then will erase all stored data in the CTG connected to Page 12 the COM port Please be careful with this function as the data cannot be recovered once erased Download CTG and Status Window The Download CTG button is used to download the data from the CTG Do not click on this button until the desired data file names and directories for the results and the time data as applicable have been set Also this button should be clicked only AFTER the CTG is in the DOWNLOAD mode as described below When data is being downloaded the current file number being sent is displayed in the status window located directly under the Download CTG button The status window then allows the user to monitor the progress of the download operat
24. ntly in that file Download Data File Name Display and Selection The time domain data for CTG 1TF systems is downloaded to a series of files with the total number of files equal to two times the number of saved records Each downloaded data set creates a DAT file and a PRM file for use by the TFS analysis software The naming of these files is done by starting with a user created base file name up to 5 characters to which the test number is appended to create the final full file name Thus if the base name is TEST the file names of the time data after download will be TEST1 DAT TEST1 PRM TEST2 DAT TEST2 PRM etc The base name is input into the Download Base Name box The data directory is set through the Download Data Directory box Please note that the CTG download software WILL OVERWRITE existing data if the same base name and directory location is used for downloading multiple sets of data Select Port The Select Port option allows the user to select which COM port to use for the data download Note that up to 4 COM ports can be displayed but that only valid ports which are currently NOT IN USE will be displayed for possible selection If no valid ports are found a message is printed in a message box at the lower left corner of the screen If this occurs then either a serial port needs to be freed up from it s current use such as running an external modem or mouse or additional COM ports must be i
25. or subsequent download This section of the manual will discuss the setting and use of the Real Time Clock RTC and the data downloading procedure Included is a discussion of the use of the Windows based download software the downloaded results data formats and typical applications This manual does not include instructions on the use of the TFS software for analysis of the downloaded data using CTG 1TF systems as the TFS software has it s own much more extensive user manual CLOCK CHECK SET The clock functions on the CTG 1T and CTG 1TF are accessed from the cal data selection 2 on the main menu Next select Download Recall 4 and then Clock Set Display 8 The currently set date and time will be displayed in the format Date MM DD YY Time HH MM SS If these settings are correct simply select Exit 2 to return to the main menu If the date or time needs to be set press 1 to select the Set Time Date option After pressing 1 the screen asks for the date in the format MMDDYY where MM is the current month DD is Naas 10 CTG Download Program Downlood CTG il No Deta Carcel Clear CTG Doentbad Base Name 5 Cher Mex Results File hame C cig ciggata deat CTGTF Select Resubs File Covwnload Dete Directory Select Pori C Comi current date and YY is the current year After entering the digits requested June 3 2002 is entered as 0
26. or the slab or wall desig 5 Be us Enter design thickness in or cm At this point use the keypad to enter the expected or design thickness of the test area This design thickness will be used by the CTG to set the range THIN or THICK Max Thick maximum test thickness see Connector below at 33 greater than the expected thickness and to select one of three peak picking algorithms which are each optimized for a certain thickness range As an example if an expected thickness of 23cm is entered the Max Thick will be set to 28cm the THIN mode will be selected and the medium thickness picking optimization routine will be used for automated data analysis If the expected thickness is not known simply enter a large value to allow the unit to search a wider range of thicknesses For thinner unknown sections such as slab or walls to be tested with the internal solenoid THIN mode enter a value of 50cm For thicker structures to be tested in THICK mode enter a value of 1m if the thickness is not known For very thin sections such as sidewalks or driveways we recommend entering 12 15cm as the design thickness The graphical display of the entire collected spectrum will then allow the user to narrow down the actual depth range for later tests if needed The computed Max Thick value is momentarily displayed immediately after the design thickness is entered The unit will not measure thicknesses greater than phe
27. out twice as long in high resolution mode as compared to the default low resolution mode Note too that for CTG 1TF systems the time data is saved and downloaded as high resolution for all tests regardless of the selected mode Batteries The rechargeable batteries in the CTG should last 14 16 hours typically on one charge if the backlight is not used or 10 12 hours if the backlight is used To charge the batteries simply plug the charger only use the charger supplied into a 110 VAC outlet 220 vac if ordered with that option and plug the other end into the jack on the right side of the CTG Allow the unit to charge 10 12 hours overnight to fully recharge Charging is best done at room temperatures to maximize battery life and to allow a full charge Note that the unit can be used while charging if desired but that this will slow down the charge rate The LOW BATTERY light on the front of the unit will light up or flash during tests when there is about Ye hour of operating time left on the batteries Operating the unit after the low battery light is on continuously may result in erratic readings or error messages Battery Replacement The batteries in the CTG should typically last for 500 1000 recharge cycles before reduced operating time from an overnight recharge is noticed The battery pack in the CTG consists of 10 A A sized batteries in a holder If needed they can be replaced by the user with new rechargeable batteries or
28. set too high and is not striking the anvil top If this message appears repeatedly on flat concrete when testing in THIN mode adjust the solenoid position downward by 2 3 mm and retest For tests done in THICK mode this message also means that the signal received was not sufficiently strong to trigger the system The most common cause in the THICK mode is a failure to impact the surface within the 6 second time window during which the unit waits for a trigger in THICK mode If this happens simply repeat the test and be sure to strike the surface within 6 seconds of pressing the FIRE key If the surface was struck but the message still appears check the transducer contact and or repeat the test with a harder impact A message of Delam Debond Press any Key THIN mode only indicates that the signal level was too high This is typical of tests on delaminated concrete or very thin material This message will also appear if a test is attempted on a table top or metal surface or if a test is done through unbonded tile or other topping material Occasionally this message may appear if testing on the end of a concrete cylinder or other undamped test sample If this is the case try re testing with less pressure or no pressure applied to the test head A message of High Signal Retest Press any Key THICK mode only indicates that the impact of the hammer was too strong and that the test needs to be repeated with a lighter impact
29. unit and the serial port is the serial port active is the connection sound is the connector plugged into the correct port 4 Verify the battery condition on the CTG unit is the low battery light on Page 15
30. with standard alkaline batteries Battery replacement is a simple matter of opening up the back of the CTG to expose the battery compartment disconnecting the battery pack connector and then replacing the batteries top and bottom in the holder After replacement reconnect the battery connector and replace the battery pack into the space in the CTG Finally replace the 6 screws removed jQoce 6 access the battery pack If the new batteries are rechargeable it will be necessary to charge the unit overnight before use as rechargeable batteries normally come in a discharged state Caution Do not attempt to recharge non rechargeable batteries such as alkaline cells as damage to the unit or personal injury may result Also only replace the batteries Page 6 with nickel cadmium rechargeable batteries or non rechargeable alkaline cells The use of Li lon or other similar batteries may also result in damage to the unit or personal injury as the charging system has not been designed for these batteries CALIBRATION The CTG measures thicknesses of concrete by measuring the time required for an echo to bounce off the back side of the concrete member being tested The thickness is then computed by using this travel time along with the speed of sound in the concrete The speed of sound in concrete can vary over a range of typically 10 15 3 000 to 4 300 meters per second m s depending on the mix design aggregate type and age o
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