220.127.116.11. DIRGA Calibration
Calibration of a DIRGA is usually performed against outside air at zero point (nowadays about 380 ppm CO2; e.g. Petz et al., 2004), and against a span gas of known CO2 concentration in end point (according to the system's measurement range) or with internal calibration cuvettes (e.g. URAS devices of ABB, Inc.). Automatic calibration can be done after switching the air flow with magnetic (or better, stepping motor) valves to bypass the insect measurement chamber (see Stabentheiner et al., 2012). The resolution of sensitive CO2 measurement equipment is down to <0.2 ppm. With appropriate care, a measurement accuracy of ~2 ppm is feasible.