Impact-Echo Instruments' products are based on research carried out by Dr. Sansalone at the U.S. National Institute of Standards and Technology (NIST) and Cornell University. The first portable, computer-controlled, impact-echo field instrument was developed at Cornell University by Professor Sansalone in the early 1990's. Impact-Echo Instruments is privately held and based in Ithaca, New York, USA.

Impact-Echo Instrument's systems can measure thickness of concrete slabs such as pavements, retaining walls, and tunnel walls. They can also determine the location, depth and extent of cracks, voids, delaminations, honeycombing and debonding in plain and reinforced structures. Testable structures include plates (slabs, walls, decks, pavements), layered plates (including asphalt on concrete), columns and beams (round, square, rectangular), and hollow cylinders (pipes, tunnels, mineshaft liners, tanks).

Instrument Components

The picture and numbered list below describe all components available for an impact-echo instrument. Configuring an instrument consists in selecting the number and types of transducers (items 2-3). The transducers are described below, together with suggested instrument configurations.

1. Impactors: a set of 10 hardened steel spheres on spring rods, used to generate the stress waves that propagate within the structure and are reflected by flaws or external surfaces.

2. Hand-Held Transducer Units: the cylindrical and pistol grip models are used to detect signals generated by multiple reflections of stress waves within a structure. See photographs and descriptions below.

3. Dual-Head Transducer: used to measure wave speed by recording the travel time of a stress wave between two transducer elements held at a fixed distance (300mm) on the surface of a structure. See photograph and description below.

4. Analog/Digital Data Acquisition System: receives and digitizes voltage-time signals from the transducers, and sends them to computer (14-bit resolution, 2 MHz maximum sampling speed on each of two channels).

5. Notebook Computer: any standard notebook with Windows operating system is suitable (see Specifications page); instruments can be purchased with or without a computer.

6. Computer Software: user-friendly, Windows-based Impact-E software (on CD) analyzes signals, performs calculations, and displays test results on computer screen.

7. Two BNC Cables: for connecting transducer units to data acquisition system.

8. Serial/USB Port Cable: for connecting data acquisition system to serial port or USB port of computer.

9. Battery Charger: input 90v - 264v AC, output 12v DC, for recharging batteries and providing power for data acquisition system.

10. DC Power Supply: input 6 -24v DC, output 12v DC, for recharging batteries in data acquisition system (connects to cigarette lighter in car or truck).

11. Printed Materials: Book: "Impact-Echo: Nondestructive Evaluation of Concrete and Masonry" by M. J. Sansalone and W. B. Streett, Bullbrier Press, Ithaca, NY, 1997, 339pp; instruction manuals; and other documents, including packing list and warranty.

12. Roll-On/Carry-On Case

 

Instrument Configurations

Three recommended configurations for an impact-echo test system, depending on the types of tests to be performed, are the following:

System A: A system three transducers including two cylindrical or two pistol grip or one of each, plus a dual-head transducer. The cylindrical and pistol grip transducers can be used for testing, with a backup available in case one is lost or damaged. Determining the depth of surface-opening cracks requires two transducers, and is most convenient using two cylindrical or two pistol grip transducers, or one of each. The dual-head transducer is used for independent measurements of wave speed. The picture at the top of this page shows the components of this system (computer optional).

System B: A system that includes one transducer for testing, either cylindrical or pistol grip, and one dual-head wave speed transducer. This will cover all possible testing needs. For determining the depth of surface-opening cracks, one end of the dual-head transducer can be used in conjunction with the pistol grip or cylindrical transducer; however this can be cumbersome in some situations. The dual-head transducer is used for independent measurements of wave speed

System C: A system that includes only one transducer, either cylindrical or pistol grip. This system is suitable for routine testing. Wave speed can be measured only if tests can be performed on slabs of known thickness in the regions where testing is to be performed. The photographs below show the main components used for routine impact-echo testing (top) and for independent measurements of wave speed (bottom).

Configuration for Testing

Configuration for Wave Speed Measurement

To measure wave speed, an impact is made on the straight line between the two transducer tips, and the time required for a stress wave to travel the fixed distance (300mm) between the two transducers is measured. For concrete with a wave speed of 4000 m/s, this travel time is 75 micro-seconds. To achieve 1% to 2% accuracy the wave arrival times must be measured to within about 0.5 micro-seconds (0.0000005 sec). This requires a sampling rate of at least 2 MHz (2 million samples per second) which is provided by our data acquisition system.

Wireless Echo System: A system designed for 2-man forensic teams. One operator performs tests on a structure (bridge, building, etc) and the resulting test signals are sent wirelessly (up to 300M) to the computer, which is monitored continuously by the second operator. Two-way radios are provided for continuous voice contact between the two operators.