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INTRODUCTION
The Olson Instruments CTG-2 system is commonly used for thickness evaluation and
rapid flaw detection on concrete and masonry structural materials. The method is
normally applied to plate-like objects such as slabs and walls, but is also used on
columns, mat foundations, and beams. The method requires access to only one side for
testing.
The CTG-2 is a powerful, hand-held device meant to be used with most Windows 7 and
Windows 8 laptop computers or tablets. The CTG-2 is designed to measure the
thickness of concrete slabs and walls in the range of approximately 3.2 inches (8.1 cm)
out to about 6 feet (1.8 m) without the need for drilling, coring, or other means. Test
results are acquired and analyzed with Olson’s WinCTG2 software, making the CTG-2
system a fully functional Impact Echo (IE) based thickness measuring system, capable
of analyzing echoes from multiple cracks and other flaws. In addition, a summary of test
results can be saved in comma separated format for use in an excel spreadsheet.
The WinCTG2 software features a graphical display of both the raw time signal as well
as the received signal spectrum (which can be saved and recalled), which allows visual
indication of data quality, easy differentiation of bad data, and even the location of
partial cracking damage. This unit 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-2, when used with the default concrete velocity value of 12,000 fps, has an
accuracy of up to approximately 10%. This accuracy can be improved to approximately
2% when the unit is calibrated for velocity at a location of known thickness.
To confirm functionality of the CTG-2, it is advised to test the unit on a slab of known
thickness or on a 6” x 12” concrete cylinder which can be readily obtained from a
concrete supplier.
The CTG-2 with automated solenoid and displacement transducer comes with a phone-
plug-to-phone-plug cable used to connect the unit to a laptop or tablet. A microphone
adaptor is included to ensure the cable will work with different microphone/headset
ports. A USB jump drive is supplied with the necessary software and a microUSB-to-
USB cable is included so the software on the USB jump drive can be downloaded onto
Windows devices. The user must supply a Windows 7 or Windows 8 laptop/tablet.
Details of the hardware and its usage are included in Section 2.0. Suggested Windows
devices that are known to work with the CTG-2 are listed in Appendix A.
