V-Meter MK IV™

The instrument has an easy to view display (320 by 240 pixels). The backlit for daylight use, makes field work easier and faster, since the operator can identify good results in seconds without the problems related with the sun light reflection on the screen. The signals can be recorded in the instrument for review on the screen or for transfer to a PC.

Typically, the 54 KHZ transducers are used for concrete testing - the signal wavelength is about 75mm ( 3 inches ). Finer materials require higher frequencies for optimum resolution. The basic V-Meter MK IV™ contains a transmitter, a receiver and a very accurate high speed electronic clock. The transmitter generates an electrical pulse which when applied to a transmitting transducer, converts the electrical energy into a pulse of ultrasonic mechanical vibration. This vibration is coupled with the specimen under test by placing the transducer in contact with the specimen. At another selected point on the specimen another receiving transducer is coupled by mechanical contact. Each transmitted pulse of energy registers on the high speed clock. The first energy wave reaching the receiving transducer is converted back to an electrical signal and turns off the clock. The elapsed time is displayed on the LCD in 0.1 microsecond increments. The unit can also display and store the resulting waveform. This ensures the operator that a proper acoustic contact has been made with the surface of the material under test.

The standard transducers for the V-Meter MK IV™ are made for a 54 KHz high Q resonant frequency with a stainless steel housing. The connector is a ninety degrees to the face of the transducer to facilitate operation and getting proper acoustic contact. A push button and special cable are added to the reciever in order to store data while taking readings. The data can later be uploaded to a computer via the Veelinx software. An adapter is provided to utilize the receiver with standard co-axial cable.

The ultrasonictransducers are typically used in one of three configurations, direct, semi-direct and indirect mode. Direct is the most sensitive method as the receiving transducer will receive maximum energy from the transmitted pulse. Since the longitudinal pulses leaving the transmitter are propagated mainly in the direction normal to the transducer face. The travel time is affected by the concrete condition along the thickness of the member. Semi-direct transmission is performed with transducers on adjacent faces. This is the next preferred method. Finally, In-Direct the least preffered. with the transducers on the same face. This should be used only when it is impossible to have access to two faces of the material under test. The received amplitude of the method, for the same path length, is only about 2% of that received signal when using the direct method. Testing for shear waves can only be performed with the In-Direct method, with both transducers on the same face as the specimen under test.