Gas Emission Real Time Instrument
The gas sensor developed for use in volcanic gases has Membrapor electrochemical sensors to measure SO2 (0-100 ppm), H2S (0-50 ppm) and HCl (0-20 ppm). A transmitter board from mebrapor is bought for each of these sensors. The sensor can be easily clicked into place on these boards and the sensitivity can be adjusted to provide a suitable zero and maximum value. A gascard CO2 sensor from Edinburgh instruments used IR absorbance to detect the CO2 present and could measure 0-5000 ppm CO2 in the gases. This also has similar zero and span adjustors. The gascard requires a 24V supply, this is provided by 2 12V batteries.

Air is pulled through a 0.2 µm PTFE filter before entering the gas sensor box. The gas then passes through the CO2 gascard, before being passed over the electrochemical sensors and out to the external pump. The pump is an Airchek 500 set to pull air at 0.8 l/min. An additional inlet and outlet to the weatherproof sensor box exposes a pressure transducer (800-1200mbar) to atmospheric pressure. In a radiation shield attached to the exterior of the box a combined relative humidity/temperature probe monitors conditions.
Gas sensor with new data logger Gas Sensor inside

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