Système d’émission de pulsations ultrasonores
- James Instruments - V-Meter MK IVMC
|Operator Reviewing V-Meter MK IV™ Data||V-Meter MK IV™ evaluating a round Column|
|The V-Meter MK IV™ is widely used and accepted for quality control and inspection of concrete. It can measure and correlate concrete strength to standard strength measurement, permitting non-destructive testing of complete structures. It will identify honeycombs, voids, frozen concrete, cracks and other non-homogenous conditions in concrete. Ultrasonic testing can be applied to new and old structures, slabs, columns, walls, fire damaged areas, hydroelectric structures, pipe, prefab and pre-stressed beams, cylinders and other concrete forms. A wide range of transducers are available.|
|V-Meter MK IV™ used on Wood Direct Mode||V-Meter MK IV™ used on Wood Direct Mode|
|V-Meter MK IV™, ultrasonic testing of wood can, nondestructively, detect knots, shakes, splits, grain orientation, windfall cracks and presence of decay and rot. Basic parameters such as modulus of elasticity and density can be calculated. Practical applications include field testing of utility poles and structures, grading in the manufacturing process, fire ladder inspection, examination of laminates and paper roll density. The velocity of ultrasonic energy pulses traveling in a solid material are related to the density and elastic properties of the material. The pulse velocity is thus a measure of density and elastic properties of the material. In transmitting ultrasonic energy through a coarse grained material such as concrete, ceramics or wood, it is necessary for the wave length of energy to be greater than the diameter of the largest grain particle. If it is not, all of the energy will be reflected back by the particles and none will reach the receiver. Typically, the 54 KHZ transducers are used for wood testing. The signal wave length is about 3 inches (75mm). Finer materials require higher frequencies for optimum resolution.|
|V-Meter MK IV™ used with Ceramic Sample|
V-Meter MK IV™ has been successfully applied to a range of ceramic products--including tile, refractory bricks and blocks, and kiln furniture--as well as graphite. In an increasing number of refractory and ceramic applications, the ultrasonic pulse velocity testing technique has been used with positive results. UPV testing has enabled users to improve their production processes, increase the integrity and quality of their products, and reduce scrap and reject rates-thereby saving both time and money. In today's economy, such bottom-line benefits are difficult to ignore.
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.
|V-Meter MK IV™ Showing
|V-Meter MK IV™
|V-Meter MK IV Standard 54KHz Transducers|
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 adaptor is provided to utilize the reciever with standard co-axial cable.
The ultrasonic transducers are typically used in one of three configuartions, 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.
|Transducers being used in Direct Mode||Transducers used in Semi-Direct Mode||Transducers used in Indirect Mode|
|Frequency range:||24 to 500 kHz, based on transducers selected.|
|Receiver sensitivity:||250 micro volts, between 30 kHz and 100 kHz.|
|Receiver input impedance:||approximately 100 k Ohms.|
|Transit time measurement:||0.1 to 6553.5 microseconds, direct digital display.|
|Measurement accuracy:||0.1 microseconds.|
|Transmitter output:||pulse 1000/500V, 2 microseconds.|
|Transmitter pulse group rate:||selectable 1, 3 or 10.|
|Gain Selection:||1, 5, 10, 25, 50, 100, 250, 500|
|Battery:||14 Volt. 4-10 hours continuous use (Lithium Ion).|
|Display:||320 by 240; backlit for daylight use.|
|Storage:||1800 plus readings|
|Software:||Windows XP compatible.|
|Temperature:||0° - 50°C|
|Instr. Weight:||6 lbs. (2.75 Kg)|
|Ship Weight:||17 lbs. (7.7 Kg)|
|Dimensions:||4.5" x 8.5" x 10.5" (114.3mm x 223.5mm x 267mm)|