Applied mineral exploration methods, hydrothermal fluids, baro-acoustic decrepitation, CO2 rich fluids
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The BGS model 216 decrepitometer

Improved electronics - 2019, 2021

The new model 216 decrepitometer is physically similar to the model 205 decrepitometer and uses the same furnace and operational computer and software but has updated and improved electronics which gives higher sensitivity and more convenient cable connections. As with the model 205, model 216 uses a standard single-board Linux computer running the Debian Ubuntu operating system. The decrepitometer operation software has a full graphical interface and operates in the X-windows environment. The temperature and counts are monitored and shown on screen during the analysis, and simultaneously plotted on screen in a separate window as the temperature rises. The data is saved to a file upon completion, and the graphical plot can also be saved as an image file or printed if required and easily regenerated from the saved data file for additional review.

This is the screen for data entry and sample analysis.

data entry and operation screen

This is the complete model 216 instrument.

model 216 decrepitometer

This is the main electronics unit incorporating the signal processing and the computer.

Decrepitometer 216 CPU

As with the previous model 205, the model 216 provides the complete computer as part of the instrument. It can be operated stand-alone with the addition of a HDMI monitor, and USB keyboard and mouse, or operated remotely across a network using the included wired lan connector.  The computer and its interface electronics enclosure is 15 * 13 * 7 cm, the power supply unit is 20 * 22 * 10 cm and the furnace enclosure is 33 * 33 * 60 cm.

Operation is the same as for the model 205 decrepitometer. The weighed sample is added to the sample tube, the sensor is added, it is inserted into the furnace, the plugs are connected and the door of the enclosure is closed. The sample information and control settings are entered into the control window and the "GO" button is clicked. The analysis then commences and a plot window shows a graph of the data as it is collected. The entire analysis is completed automatically without further user intervention. At the end temperature, the furnace is turned off and the control window re-appears to allow analysis of additional samples. The plot remains in view, with additional plot windows being created for additional samples. It is necessary to allow the furnace to cool before analysing subsequent samples. The saved data files include the operation parameters and sample details as well as the decrepitation count values. These files are plain text and can be viewed or edited in any text editor software as well as used by Gnuplot or other graph plotting software.

Samples of 0.5gm are normally used while samples as small as 0.2 gm or up to 2 gm can be analysed according to the fluid inclusion abundance in the sample. The heating rate used is almost always 20ºC per minute, but the instrument can also be operated at 10ºC or 40ºC per minute. Analyses are usually performed on quartz samples, but other minerals containing fluid inclusions can also be used, such as carbonates, feldspars and opaque minerals such as haematite and magnetite. Sulphides can also be analysed, but they can be corrosive and this reduces the life of the temperature sensor. Quartz samples are usually analysed up to 620ºC because there is no significant activity above the alpha to beta phase transition at 573ºC, however the instrument can be used for analyses up to 800ºC.

The system can be installed in a normal quiet laboratory location as ambient sounds are suppressed. However loud sounds or vibration can interfere and should be avoided. It can be operated remotely across a network and the room can be unoccupied during the analysis.

Auxiliary software  is provided to simplify plotting of the previously saved data files. These saved data files can still be plotted using Gnuplot which is very comprehensive but driven from the command line. The plotting utility software still uses Gnuplot but is specifically designed to plot decrepigram files and has a fully graphical interface. It facilitates superimposing multiple results on a single plot to allow inter-sample comparison. The plots are viewed on screen and can also be saved as .png image files.

This is a screenshot of the plotting software (V3.0)  for decrepigram files in operation.

plotdgm with legend and multiplier

Files for plotting are selected in the "select files" window shown here in the lower right. Multiple files or groups can be chosen and added to the main listing in the left window. Files do not all need to be in the same directory. The files to be plotted on a single graph are then selected in the left window and multiple files can be plotted together in a single plot window as shown in the upper right. Comments can be added to individual files to appear in the legend on the plot. Selected files can also have the data multiplied so that all the plots show nicely at the same scale. Additional selections and plots can be prepared as all the plot windows remain visible to facilitate comparison and interpretation. The plots can also be saved as .png graphics files in one of 3 different sizes for addition to presentations or printing etc.

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