Calibration of the CUMA Diagnostic Unit


  1. Eaton, D.J.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Dynamic mixing of breathing gases in a diving set requires constant monitoring of the oxygen partial pressure to alert the diver of failures. The CUMA (Canadian Underwater Mine-countermeasures Apparatus) is a self-contained, underwater breathing apparatus that mixes oxygen and a diluent gas (in CUMA helium is used) to provide the diver with a breathable mixture. The mass flow of oxygen remains constant throughout the dive while the helium flow increases linearly with depth; thereby, holding the oxygen partial pressure of the gas mixture constant. A secondary gas supply circuit known as the bypass circuit provides breathable gas but the oxygen partial pressure is not held as steady. A method is required to accurately monitor the oxygen content of these gas mixtures. In the CUMA a galvanic oxygen fuel cell is used to measure the oxygen partial pressure of the mixtures during the dive as well as during the pre-dive calibration of the gas mixing circuits. It is important that the oxygen analyser itself be calibrated to ensure the best calibration of the apparatus and the safe performance during a dive. The current procedure calibrates the CUMA oxygen analyser to 1.0 atmospheres, absolute (ATA). This distributes the analyser error across the full operational range of the CUMA, i.e., 0.18 ATA to 1.8 ATA. TRUNCATED
CUMA (Canadian Underwater Mine-countermeasures Apparatus);Air bubbles;B5 oxygen sensor Teledyne;Closed circuit breathing apparatus;Oxygen sensor;Partial Pressure Oxygen;Closed-circuit Breathing Apparatus;Semi-closed circuit Breathing Apparatus
Report Number
DCIEM-TM-2000-001 — Technical Report
Date of publication
01 Jan 2000
Number of Pages
Hardcopy;Document Image stored on Optical Disk

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