BATMIDAS-P is the acronym for the new high performance portable Windows NT based
mono/multi-channel (up to eight channels) ultrasonic data acquisition and analysis system
with detection of position based on air borne ultrasonic signals.
Real time 1D and 2D display of ultrasonic signals and actual position of the probe allowing
the acquisition of co-ordinates without mechanical devices is its most powerful feature.
The non-mechanical positioning system is based on a 40kHz ultrasonic transmitter linked up
to the UT probe. The 40kHz air borne ultrasonic signal is gathered by three (up to six)
receivers located at known positions thus obtaining the time of flight of the mentioned signal.
With these data and by means of triangulation techniques the exact position of the emitters in
the user selected reference system is obtained with accuracy better than 1 mm. Up to three
emitters can be used in order to obtain not only position but orientation of the inspecting
probe.
In this way, A, B, C and D-scans UT (radio frequency and echoes) registration can be
obtained by the in-field manual inspection without the need of costly price and maintenance
mechanical positioning systems and with comparable accuracy and repeatability results.
The UT linear/mono/multi-channel electronics allow high-resolution inspections, adding
large bandwidth amplification, pulse adjustable in frequency and voltage, and 80MHz/8 bits
digitisation. Those capabilities meet the main Aeronautic Industry specifications.
The whole system is highly integrated and installed on a Portable Industrial PC. The powerful
data acquisition software is Windows based allowing fully controllable parameters of the
electronics, easy calibration process, on-line display of A and C-scan of ultrasonic data with
actual position of probe, echo-dynamic signal on A-scans, and automatic backup of data
without interruption of inspection.
The BATMIDAS-P system is conceived for the in-field or laboratory manual and
semiautomatic general purpose ultrasonic inspections, pipes and tanks inspection, redundant
systems, manual inspection of special composites materials in the Aeronautic, Power
Generation, Automotive and other industries in general.
BATMIDAS – P (see Figure 1) consists of a portable industrial computer integrating a 3D
positioning device (BAT) and a versatile ultrasonic electronics (by Metalscan).
Fig 1: Picture of the BATMIDA-P system, including the portable computer, BAT
device, UT electronics, and ultrasonic sensors.
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BAT is a positioning device that gives the three-dimensional coordinate of a probe (or any
other element of interest), as incremental encoder signals, while it is in movement. This
device is based on 40 kHz ultrasonic pulses and it doesn't use mechanical components. In a
three-dimensional space, the device only requires three receivers, freely positioned in the
working zone, and one emitter, next to the inspection probe. In addition, a temperature sensor
is used to take into account the small variations that suffer the sound velocity with the
ambient temperature.
The system provides the three-dimensional position by means of three encoder signals in a
Cartesian system. Optionally, coordinates in a polar reference system (for pipe inspections)
and orientation angles are available. In this case, more than one emitter (up to four) are used
in order to achieve angular coordinates, and more than three receivers (up to six) are available
in order to select dynamically during inspection the three most suitable receivers in terms of
the instantaneous signal quality.
BAT is connected to the portable PC by the parallel port and includes a dedicated software
that runs concurrently with the acquisition software. This software, which allows the user to
define the appropriate coordinate system by a simple procedure, calculates the position of the
emitter from the times of flight detected in the three receivers, sending back the results to the
BAT device which generates the encoder signals. The BAT device triggers continuously the
UT signal acquisition as new coordinates, with a resolution ranging from 1 to 2 mm, are
produced. The minimum time elapsed between two consecutive coordinates is 10 ms, which,
according to the sound velocity in air, allows a maximum emitter-receiver separation of 3
meters. If larger distances are required, several BAT units can be plugged in chain optionally.
The UT electronics provides a wide variety of parameters to be controlled. The probe can be
excited either with negative or bipolar pulses or bursts of 1 – 15 pulses, with a pulse width
ranging from 25 to 1250 ns, amplitudes up to 200 V, and different damping impedances (33 –
90 .). The receiving stage consists of a linear amplifier with a gain adjustable dB by dB up
to 70 dB, a bandwidth of 20 MHz (at –3 dB), an attenuator of 0 – 40 dB, and a low-pass filter
with a cut-off frequency selectable in the 1 – 16 MHz range. Distance-Amplitude Correction
(DAC) curves with 31 programmable segments are also included in this electronics. The UT
signal is digitised by a flash 8 bits A/D converter at a frequency in the 40 – 80 MHz range.
BATMIDAS-P software, called MIDAS, takes profit of the windows environment and
multitasking of Windows NT technology. MIDAS consists of three main modules for
calibration, acquisition and post-evaluation purposes. The UT calibration module (see Figure
2) allows the user to select and optimise the ultrasonic signals to be recorded during the
acquisition, while performing at the same time calibration of the time axis (sound path) and
signal amplitude using reference signals from standard pattern blocks.
These operations are performed with real-time on-screen display of the signal being used for
calibration, such that the operator may immediately check the effect of his actions on the
signal quality. Among different functionalities, the calibration module includes the following
ones:
Channel Summary: Table for the calibration conditions, including: Probes used, Field and
type of information to be stored, spatial resolution, expected data file size and data flow,
expected inspection time, etc..Customisation: Default position of the windows, type of cursors, colours, units, etc.
Fig 2: Example of the UT calibration screen in MIDAS.
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Signal window: Signal scans (both complete and zoomed), UT gates and the DAC curve, if it
exists, are displayed with selectable scales from different units. Gate and DAC parameters
may be adjusted either graphically or numerically. Along with the signal, it is possible to
display the accumulated maximum signal, and scrolls of the echoes detected.
Cursors: Amplitude, time and frequency cursors for both absolute and differential measurements
in the units selected are available in different modes (local peak, free movement, signal value,
absolute maximum, average value, RMS value).
Definition of probes: Probe type (Single/Dual crystal), Name, Frequency, Focus, Offset,
Skew and Type of Wave(s) generated/received.
Pulser/Receiver Control: excitation pulse voltage and width, damping, attenuation, gain, and
type of connection to the probe (Pitch-Catch/Pulse-Eco) can be configured.
Filters: The low-pass, band-pass and high-pass filters available in the hardware may be
numerically and graphically adjusted or disabled.
DAC curves: Graphical and/or numerical definition of DAC points.
Gates: Beginning, End, Threshold and Maximum number of echoes to be detected.
Digitisation: Signal type (Linear/Logarithmic), sampling frequency, beginning of field to be
stored, field depth, amplitude offset correction, storage of complete signal and/or echoes only
and use of the echo-start technique.
FFT: Either Linear or logarithmic display are available.
Measurements: Peak value, rms value, offset and DC signal component.
Calibration: Automatic calibration from either two peaks or one peak and sound velocity.
The acquisition module is in charge of gathering all the information corresponding to the
inspection previously planned (part, probes, probe-holder module to be used, manipulator and
scan to be performed) and, along with the calibration, where the necessary electronics.adjustments have been defined, of undertaking the inspection, recording the data for
subsequent in-depth evaluation. During acquisition, the inspection A-scan or reconstructions
in the form of B-C-D views are displayed. There is also a simultaneous control of the integrity
of the data being received for detecting possible data losses, duplications and/or corruption.
The following capacities are included in the acquisition module and basic presentation:
Control panel: This includes a series of indicators and alarms which informs the operator about
the instantaneous status of the system (activity, data flow, coordinates, etc.).
UT window: It is used to monitor the progress of the acquisition in a variety customized
windows showing, echoes, the signal Ascan and 2D projections with independent colour
scales (both discrete and continuous) for amplitude and sound path. A cursor permits the user
to know at any moment the UT information corresponding to any position of these
representations.
In the post-evaluation module, the user can configure the screen in order to extract the most
interesting information from each inspection. This screen can be configured with an arbitrary
number of graphic objects including Ascan, FFT, numerical and graphical views of echoes,
scroll windows, thermometric indicators (vumeter type) for simple magnitude (attenuation,
thickness) representations, 2D projections (C-Scan, B-Scan, and D-Scan) and 3D Views. This
system manages two independent palettes, one for the amplitude and another for the sound
path in which the user can set up the number of colours and gradation type in 2D and 3D
projections. This system also provides different tools such as echoes and geometrical filters,
measure cursors and rulers, zooms, boundary, text and identification marks, statistic tools,
multi-file evaluation, and printing tools.