Harry Potter And The 'Ionisation Chamber' !!

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Find out how to construct an ionisation chamber. Also learn how a PicAXE-08M microprocessor can measure the voltage drift rate of an ionisation chamber.

    Figure: Harry Potter                                   Figure : PicAXE Ionisation Chamber

This simple radiation detector uses a PicAXE-08M microprocessor to measure the voltage drift rate on an ionization chamber’s sense wire, eliminating the need for a high-value resistor. An electrometer-grade JFET is used to buffer the voltage on a sense wire inside the chamber, and a PicAXE microprocessor measures the rate of change of that voltage,  periodically discharging the wire through the JFET’s gate-source junction. This unorthodox way of discharging the ion chamber wire eliminates the need for a special, low-leakage switch, and takes advantage of the PicAXE’s ability to use the same pin as an analog input or a digital output.

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