| abstract |
Calibration of a measuring unit comprising a pick-up head for determining the concn. of gases, is described esp. for use with heated pick-ups for the transcutaneous determination of gases, esp. oxygen concn. in the blood. The pick-up is successively subjected to two different environments comprising different environments comprising different, but known, concns. The calibration volume is localised to a small space by comparison with the pick-up itself; in this small space the known concn. value is produced and maintained, immediately above the actual measuring zone of the pick-up and spatially limited to it. Pref. a 100% humidity is produced and maintained in the calibration vol. by insertion of a water-satd. sponge or filter paper and subsequent covering of this space with a thin foil. The two calibration steps can be carried out quite simply without the use of pumps, thermostats, water baths, humidity meters and other apparatus. In the first stage, the device is brough into contact with air, while in the second stage the satd. filter paper is replaced by a plug of sponge contg. an oxygen-absorbing material to reduce the oxygen partial pressure to zero. |