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By default this page displays the dose rate in μSv/h, i.e. millionths of a Sievert per hour (it will theoretically also go to mSv/h and possibly even Sv/h if the hardware is still working at that point). Purists will, however, argue that it is not strictly valid to report the output of non-energy-compensated Geiger tubes in terms of dose rate. Technically speaking they are correct, however it is the rule rather than the exception for amateur monitoring stations to report in μSv/h. For the benefit of the purists, you can switch to displaying the dose rate in μR/h, or for extra purity, a count rate in CPM.
Since the actual count rate will depend on the number of tubes in service at the time, I have, for consistency, reported the rate as the average rate of all available SI-22G tubes. I.e. the rate is reported as if the station consisted of a single SI-22G tube (but one which can resolve fractions of a count).
The nature of a Geiger counter is such that the timing of the counts varies randomly, this creates noise on the dose/count rate signal. This noise can be reduced to a large extent (but never completely eliminated) by applying a filter. We use a 1 hour running average filter for this purpose. It is recommended to leave filtering on (the default option) in order to get a better idea of the dose rate. Viewing the unfiltered data is mainly for debugging purposes (e.g. detecting if the counter has dropped out for a short period), but can also be used to identify very brief peaks in radiation level that may be flattened by the filtering process.
If viewing unfiltered data, you are limited to viewing a maximum time period of 48 hours. There is no reason to view large amounts of data in this mode as it just becomes a continuous blur.
Time and Date are always shown as local time for this server. This is GMT+10:00 Brisbane time (no daylight saving).
You can either view the last "X" time period (from 1 hour to 28 days), or a historical period between two selected dates. Historical data is always displayed midnight-to-midnight and is limited to displaying up to a month's worth of data at a time.
The first Geiger counter was installed 16:20 19th Sept 2017 and data is available from then onwards. The second Geiger counter was installed on 15:49 10th Oct 2017, and data from this time on the system will have (slightly) improved accuracy.
The data displayed here has some statistical error associated with it. This is much reduced, but not altogether eliminated, by filtering. In order to get an idea of what variations in the rate are real and what are the result of statistical noise, you can turn on Error Limits. This will draw two lines on the screen, which are set at three Standard Deviations plus and minus the average value. What does this mean? It means that under normal conditions, any deviation of the trace outside of these lines has a 99.7% chance of being a real deviation rather than statistical noise.
This should be used as a rough guide only; it is not valid if the rate is steadily rising or falling. Also, in unfiltered mode you are likely to get occasional points outside of these lines. In unfiltered mode, there may be in excess of 1000 points plotted and you can expect on average 3 points per thousand to exceed these limits just by chance.