Geiger Counter Gammascout

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Geiger Counter Gammascout
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The Gammascout Geiger Counter is a calibrated measurement instrument for alpha, beta and gamma rays.
In a PELI Case 1040 it can be used for underwater measurements.
The central processor is a MSP430.
The USB version uses a FT232BM for the conversion USB to UART for the MSP430.
Weight: 145 g, size: 164 x 72 x 31 mm.
The hardware is good, but the software is awful: For a plot of the measured and read values (dose rate/count) you first have to use the Calculate-button and than you find a button for show; the Display-Button shows only a log. The program does not store the parameters, e. g. 2d plot of the dose with not numerics, it can't be terminated via Alt-F4, on my Notebook with a CoreDuo T2050 (1,6 GHZ, 1 GB RAM, MS-WinXP Prof. ) it needs 1 minute to start (every Quake game starts much faster) and sometimes the mouse pointer is invisible in the program window. For clearing the gammascount memory you have to read out the memory, even if you have done so one minute ago, and the program can use only one of the first (virtual) ten serial ports which are often already used by a bluetooth driver.

The data sheet of the geiger tube LND 712 says that with a shielding consisting of 50 mm Pb and 3 mm Al the maximum CPM rate is 10 CPM. Because with 20 CPM the dose rate shown by the Gammascout is about 0.2 µSv/h, this means the dose rate caused by the hard cosmic rays, which can pass the 50 mm Pb + 3 mm Al shielding, is about 0.1 µSv/h.
The gamma sensitivity shows that the saturation dose rate is about 10 mSv/h, at a pulse rate of 10 kHz. So you can't measure much less than 0.1 µSv/h and not more then 10 mSv/h with the Gammascout.
Another restriction are that a geiger tube commonly detects only about 5 % of all incoming rays and that the Gammascout shows the dose rate for "common" radiation (gamma from ⁶⁰Co), with the radiation weighting factor of 1, but the radiation can have a higher factor and the Gammasout can be less sensitive. Examples are low-energy alpha and beta rays which can't get into the tube and therefore can not be detected, but they have a high radiation weighting factor.
The LND 712 data sheet says nothing about the lifetime, but a typical geiger tube lifetime is 10 billion pulses, which is, at the usual activity of 20 pulses per minute, 951.3 years. Because of the flash memory of the MSP430 the effective life time limit is about 30 years, when you change the battery every 10 years.
The lifetime can be extended by re-flashing the firmware via the JTAG interface connector (close to the left side of the MSP430).
Another restriction is the size of the internal flash memory: If the logging interval is set to one hour, it is full after four weeks.