The accuracy of dry gas meters at continuous and sinusoidal flows

Dry gas meters are used in physiology laboratories to measure minute ventilation. The accuracy of these meters must be known since an error, of for instance 5%, affects the subsequent calculations for oxygen consumption by the same amount. Two precalibrated DTM-325 dry gas meters (American Meter Co., Philadelphia, PA, USA) were therefore tested for accuracy against a 350 l Collins chain-compensated gasometer. Provided that at least 25 l was passed per measurement then: a. continuous flows (air saturated with water vapour) between 60 and 150 l.min-1 were measured with an error of < 1%; and b. sinusoidal flows (ambient air) between 8 and 100 l.min-1 were misread by < 1% and the error was still within 2% at 140 l.min-1. It may, therefore, be concluded that the two precalibrated dry gas meters studied are valid volume measuring devices.