Accudata Ltd : Mini-SuperGraph (Article published in Quarry Management magazine Feb 2008)
The Mini-SuperGraph from Accudata is a unique seismograph in that it allows different set-up parameters to be saved for immediate retrieval and use. For example, a user may store their name, a location name, the distance to blast, maximum instantaneous charge, trigger level, sampling rate and scan time for several different monitoring locations. This means that upon arrival at a specific monitoring location, when the weather conditions may be cold, wet and windy, the user merely places the two sensor units, switches on the seismograph and selects their set-up for the that location. The above sequence only takes a matter of seconds thereby considerably easing the operator’s burden.
Nomis’ accuracy is well known and at the start of each monitoring period, a calibration reference pulse is sent to each of the three geophone sensors. These reflect the signal back to determine that the system is within its calibration limits. The calibration pulses are displayed adjacent to the three vibration waveforms on the report.
After triggering, the LCD display shows the event number, date and time, highest levels of peak particle velocity (PPV) in mm/s-1 in all three axes (Radial, Transverse and Vertical), together with the frequencies and air over-pressure in dB(Linear Peak). The data from any stored event may be reviewed on the LCD display. After downloading the data to a computer, the powerful software produces a very detailed yet crystal clear A4 report-ready print-out.
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Looking at the printout on the left ………..
The company name and telephone number is shown, together with the filename, location, the date and time, the operators name, the location, event number, record length, sampling rate and last calibration date. There is also a place for any relevant notes.
All the required details are shown, everything necessary for a complete record of the blast, including the distance to blast and the weight per delay. The scaled distance is then calculated which may be used as an axis reference point in the development of a regression line.
The trigger level and vector sum are shown and the measured levels of peak particle velocity, together with their dominant frequencies, in each axis, and the elapsed time in milli-seconds from triggering to the peak are tabulated along with the air over-pressure in dB(L). Also shown on the scaleable graph are the calibration pulses, showing that the instrument is functioning correctly and accurately in each channel.
If displacement is selected within the user set-up, then its value, in mm, will also be displayed.
Finally, The BS7385 Part 2 graph shows frequency distribution with each axis having its own letter represented in colour so that it would be immediately obvious, at a glance, if levels had been exceeded. If used overseas, The USBM or DIN Standard Graphs may be selected within the user set-up.
The Mini-SuperGraph may be triggered several times, with no wait time between events and at least three hundred two second events may be stored in memory.
The integral gel battery is able to power the instrument for many days, or even weeks, before re-charging is necessary and if the seismograph is to be left running in an unattended mode, the battery life may be further extended by the use of the in-built timer function. The timer may be set so that the instrument switches itself on and off at pre-set times during the week and to remain off every Saturday and Sunday, or off just on Sundays. In addition, to extend battery life, the LCD goes blank after a pre-set time between two and sixty minutes determined by the user. The default is 2 minutes.
The standard sampling rate is 1024 samples per second but for diagnostic work alternate sampling rates of 2,048 and 4,096 samples per second may be selected. A factory fitted option enables a sampling rate of 8,192 samples per second.
The SuperGraphics software supplied with the Mini-Supergraph for transferring data from the seismograph to a computer is very powerful, although as the program is navigated by using smart-icons, it is also very easy to use. After downloading, files are located in a directory within the SuperGraphics directory but may be stored in any chosen directory for easy archiving.
With the Mini-SuperGraph connected to the computer, a list of stored events is shown. A single click selects all the events to be downloaded or, if it is obvious that there are spurious events, these may be ignored with just those of interest being selected for download.
When the event data are downloaded, the software enables the user to perform various post processing functions. It is possible to highlight and zoom into areas of the graphs that may need closer examination. With a single click, a Fast Fourier Transform (FFT) plot may be generated, or the event data may be exported with a single click into a spreadsheet.
Within the user set-up options, there is a choice of six languages, English, French, Spanish, Italian and German.
If the Mini-SuperGraph is to be used for long term unattended monitoring, the instrument is able to run from an external power supply or a solar panel. Remote communication and downloading may also be carried out if the seismograph is connected to a modem.
The Mini-SuperGraph is the result of years of research and development that builds upon the previous generations of seismographs and by utilising the very latest technology, provides a very compact, easy to use, powerful seismograph that records everything necessary to fully comply with vibration monitoring regulations when blasting. In motor car terms this seismograph would be described as being ‘fully loaded’ and it is difficult to envisage how it could be bettered and yet it is so easy to use that an instruction book is hardly necessary.
The Mini-SuperGraph is supplied in a carrying case with a tri-axial geophone sensor unit, complete with three removable ground spikes, air over-pressure microphone with windshield and support mast, a download lead, a battery charger, the SuperGraphics software, twelve months warranty, a calibration certificate, a quick-start guide and full user instructions.