DOP3000 overview

Like all other ultrasonic Doppler velocimeters manufactured by Signal Processing SA, the DOP3000 uses pulsed ultrasonic echo technique to measure velocity profiles. This instrument has been designed to fit user's request in terms of specifications and ease of use and budget.

The DOP3000 is a modular instrument and can be concider as a Budget base + upgrades software packages.
Starting with a basic affordable instrument, it can evolve to become a powerful equipment capable of measuring in real time high resolution velocity profiles at a rate of just a few ms. Upgrades can be done simply by the user, step by step, by adding optional software packages.

In its basic version, the DOP3000 used a single emitting frequency, and can measure up to 1000 profiles. The instrument selects automaticaly one of the two available spatial resolution in order to cover the selected depth with a maximum of 100 avaialble gates. Two types of data profiles can be recorded, the velocity profile and the echo profile.

Important advise

It is highly recommended to use the UDOP simulation software when selecting software packages. In simulation mode, UDOP offers the possibility to select/unselect specific software packages. You will be therefore able to see the improvements due to the installation of the selected software packages.

Additional software packages

	Extended number of gates software package Adding this package enables the user to change the number of gates in which the velocity is computed, and to place the gates anywhere in the measuring range. Therefore it is also possible to change the position of the first measuring gate, if for instance the velocities close to the transducer are not of interest or are simply not measurable (gates outside the flow region). The functioning parameters that can be tuned when this package is installed are the following: Number of gates Up to 1000 gates can be used and placed along the ultrasonic beam axis. Starting depth The starting depth defines the position of first measuring gates. It is the distance between the surface of the transducer and the first gate. Defined in mm. Acquire raw data Up to 15'000 couples of I and Q demodulated signals can be recorded. (only available if the package "extended resolution" is installed) When a high resolution is desired over a large depth of measurement, one has to increase the absolute number of measuring points or gates. Another case where this option package is useful is when the volume to be investigated goes so deep that even with a coarse resolution, the measurement cannot be done at the end of the volume to be measured. When the transducer has to be placed quite far away from the beginning of the volume to be investigated, using this package allows to remove irrelevant information from the gates where no flow exist, thus saving memory for the useful information.
	Extended resolution software package The extended resolution package lets the user set the distance between two consecutive gates, as well as the size of these measuring gates. The basic DOP3000 automatically sets the resolution to fine mode or coarse mode depending on the maximal depth of measure selected. The present option package lets the user select any desired resolution (i.e. gate spacing) between 0.12 mm (166 ns) and 15 mm (20 micro second), as well as the length of these gates. The functioning parameters that can be tuned when this package is installed are the following: Resolution It is the distance between the center of two adjacent gates. Defined in nanoecondes and in mm. May be selected between 166 ns and 20 microseconds. Thikness of the sampling volume The thikness of the sampling volume is the distance, measured along the US beam, for which all the echoes issued from particles inisde that range are combined together in order to give a single echo value. Its value is defined by both the burst duration and the electronic bandwidth of the receiver of the DOP3000. It covers the range from 0.8 to 4 mm Burst length Defined in number of cycles, between 2 and 32 and can be automatically setup by the UDOP software. Maximum PRF value The PRF value can be as low as 0.1 second, which allows the measurement of very low velocities. Acquire raw data Up to 15'000 couples of I and Q demodulated signals can be recorded. (only available if the package "extended resolution" is installed) Even if a measurement of velocity every centimeter of depth can generate a decent velocity profile in a pipe of 1 meter of diameter, it will be an insufficient spatial resolution in a pipe of a few centimeters of diameter. This package enables not only the definition of the spacing between two adjacent gates but also each size of the gate along the US beam axis.
	Advanced compute software package In its standard functioning mode, the DOP3000 computes and displays a velocity and/or the echo profile. This option package enables the instrument to show many more relevant measures that helps to characterize the liquid and its flow. Among them are the energy of the filtered echo, the velocity of a chosen gate as a function of time, the flow across a section of a pipe. Moreover this software package improves the measurement by applying filters and also offers a powerfull method to overcome in realtime the aliasing limitation The added curves that can be computed and displayed when this package is installed are the following: Energy profile Displays the Doppler energy profile. This profile is the filtered echo profile, filtered by an IIR (infinite impulse response) filter. V(t) Velocity as a function of time for up to 4 different selected gates. Defined in mm/s. Power spectrum of a single gate This display gives a detail information on the spectral content of the echoes coming from a defined gate Velocity and time space This mode shows in the first display the instantaneous velocity profile and in the other display its evolution versus time, in which the velocity values are color coded. Velocity profile and flow rate Computes the instantaneous flow rate based on the position of 2 cursors placed on the velocity profile. A cylindrical section is assumed. Additionnal features of this software package are: Selectable number of emissions per profile This allows to precisely adapt the acquisition rate and the quality of the measured profiles in case of non assisted operating mode Variable origin of the velocity scale This allows to give more space to positive or negative velocities. Realtime filters A moving average filter or a mediane filter can be applied on any displayed profile in order to reduce the variance of the measurement. Cursors on graph available These cursors display the velocity and the depth values, and their statistical values ((mean, standard deviation, minimum, maximum). The cursors always follow the curve. Auto correction of the aliasing Two methods allow to perform a realtime the correction of the aliasing.
	Variable Ultrasonic Frequency software package The basic DOP3000 can only operate at one single ultrasonic frequency that the user has to chose when he purchases the instrument in the range of 0.5 MHz, 1 MHz, 2 MHz, 4 MHz, 8 MHz or 10 MHz. Therefore, the only choice he has left for the transducers he will use is the diameter of the piezo. Adding this package enables him to use his DOP3000 at any ultrasonic frequency in the full range of 0.45 MHz to 10.5 MHz, with an increment of 1 kHz. Changing the ultrasonic emitting frequency will not only improve the spatial resolution but also enable to adapt the velocity scale to a desired value, as the Doppler frequency shift is directly linked to the emitting frequency. The functioning parameter that can be tuned when this package is installed is the following: Ultrasonic emitting frequency Installing this package will greatly enlarge the range of transducer that can be associated with the DOP3000 and therefore the possible application. Depending on the application, very different kinds of ultrasonic beams shape and frequency can be optimal for measuring velocity profiles. While low ultrasonic frequencies are best for highly attenuating liquids, higher frequencies are sometimes needed in order to achieve a better spatial resolution over the Z depth axis. Sometimes low frequencies are needed in order to increase the range of mesurable velocities. More advises on choosing the best transducer for each application can be found in the transducers selection guide.
	Advanced record software package This software package enhances the built-in recording features of the DOP3000. It provides powerful editing and processing of the data to be recorded: The functioning parameter that can be tuned when this package is installed is the following: More profiles Up to 64'000 profiles can be recorded. Multiple blocks of data in file Possibility to record more than just one set of profiles (block) per file. Profile selection Possibility to preview profiles stored in internal memory to accurately select the first and the last profile that must be contained in the saved file. Update data file Update in a single pass many UDOP binary data files to the latest software version. Skip profile Allow to extend the acquisition time to many hours. Pre-record capabilty Possibility to store events that happened a few seconds before the Record button was pushed. Configuration parameters 9 different configurations can be saved.
	Variable Time Gain Control software package This option lets the user manually set the TGC amplification. He can set a constant amplification gain, a slope amplification (which increases exponentially the gain as a function of the depth), or define gains in up 1024 to user-defined zones. The functioning TGC modes that can be used when this package is installed are the following: Automatic An optimal TGC curve is automatically computed in order to avoid strong echoes or low energy gate problem. Uniform The amplification coefficients are the same for all gates. Slope The farther the gates are from the transducer, the more the echo signal is amplified according to an exponential slope (a line on the dB scale). This slope is defined by two values, at the nearest and at farther depths. Custom The user can fine-tune the TGC in any gates or group of gates independently. If a constant amplification factor is applied to the echo signal scattered by a highly attenuation liquid, the echoes from far away will be so weak that the velocimeter won't be able to compute accurately the velocity of these gates. On the other hand, applying a higher amplification factor to the gates far away will provide a more powerful signal to the correlation algorithm, without saturating the echo from the first gates.
	Advanced Trigger software package The smart trigger capability of the instrument loaded with this package allows to synchronize the acquisition to any periodic or non periodic event. When this package is installed, many trigger option can be set, such as: Trig on external BNC low The recording starts when the the voltage on the BNC connector called Trigger falls to 0 V (CMOS). Trig on external BNC high The recording starts when the the voltage on the BNC connector called Trigger gets to 5 V (CMOS). Wait after trigger Enables to set a delay between the trigger signal and the beginning of the recording. Pre Triggeer Enables to record few profiles that happened before the trigger event. Automatic receording capability Allows to store automatically the meaured profile and to repeat the acquistion by waiting for a new trigger event.
	Sound speed software package This package allows to measure the sound speed or sound velocity, in any kind of liquid when connected to the DOP3000 velocimeter. The measurement is based on a phase analysis of an echo generated by a plate, placed at a known distance from the surface of the transducer. The speed of sound in the investigated liquid has to be known for the DOP3000 to measure calibrated velocity profiles. The more precisely the speed of sound is known, the more accurate is the velocity value delivered by the DOP3000. For most common liquids, speed of sound at room temperature can be found in the literature (and even on our website). But some liquids are sometimes so specific, or used at such temperatures that a precise value of the speed of sound cannot be easily found. In such cases, it can be needed to measure the speed of sound in the specific user's conditions.
	Ultrasonic Field Measurement software package This software option enables the DOP3000 velocimeter to measure the ultrasonic field generated by a transducer connected to the probe in/out connector. The software automatically computes and detects the intensity and position of an echo issued from a small sphere moved perpendiculry to the US beam axis. By repeating the measurements at different depths it is possible to determine the divergence of the US beam, and therefore to have a much precise knowledge of the shape of the sampling gates.