The same transducer is used to both transmit and receive the ultrasonic signals. Just after the emission of the ultrasonic burst, the transducer is switched from the emitting mode to the receiving mode. The incoming echoes are then amplified, using a time depend amplification (Time Gain Controlled - TGC - amplifier), in order to compensate the attenuation of the ultrasonic waves during their propagation in the analyzed liquid. Following the amplification, gates are formed by sampling the echo signal. The depth of the gate is computed by measuring the time delay between the emission of the ultrasonic burst and the reception of the echo part corresponding to the considered gate. The thickness of all the gates is defined by the burst length and/or the bandwidth or the receiver. In order to compute the velocity in each gates, many emission are sent. These emissions form an array of time series data values, from which the mean Doppler frequency is computed by a powerful auto-correlation algorithm. The resulting velocity information is then displayed on the TFT color screen of the velocimeter and recorded in its internal memory.
The investigated liquid must contain particles. The size of the particles must be smaller then the wave length in order to avoid any diffraction of the ultrasonic beam. Hopefully this is often the case and most of liquid contains enough very small gas bubbles, dust or impurities. And when it is not the case, we can provide seeding solutions.
The ultrasonic probe can be placed directly in contact with the liquid or coupled to the wall of the container by means of an ultrasonic gel. The coupling medium guarantees a path for the ultrasonic waves.
One of the most important parameter is the choice of the ultrasonic probe. This choice is generally based on:
In order to cover a wide range of applications, the included digital ultrasonic synthesizer allows to generate any emitting frequencies between 0.45 MHz and 10.5 MHz, and our standard and custom probes can be delivered in many different housings.
The DOP2000 not only measures instantaneously velocity profiles, but also the Doppler energy profiles, echo profiles, spectral density (FFT), histogram, the flow rate and even the ultrasonic field generated by an attached transducer. By means of an external control unit, the DOP2000 can measure in real time a complete 2D or 3D velocity field. The included variable spatial resolution filter allows to adapt the size of the sampling volume to the application and therefore improves the signal to noise ratio of the measurements.
All the ultrasonic parameters (Frequency, PRF, TGC..) and the processing conditions (number of gates, filters...) can be defined by the user. The smart trigger capability of the instrument allows to synchronize the acquisition to any periodic or non periodic event. This high degree in flexibility can be apply to any of the 10 channels multiplexer (available in option) and up to 32’000 profiles can be recorded in binary or ASCII format. A separate emitter output connector allows to use two different transducers for emission and reception.
Operating in a Windows 9x® environment, the velocimeter can be adapted to your applications with only few mouse clicks. The measured profiles are displayed on a bright 800x600 TFT colour screen and are recorded in its internal memory or send through the build-in Ethernet connection to any storage device within few milliseconds.