CHARACTERIZATION OF A DENSITY-CORRECTED ULTRASONIC PNEUMOTACHOMETER FOR HORSES

A density-corrected ultrasonic pneumotachometer designed specifically for horses (UF202) was evaluated and characterized with the aid of a c ustom-built apparatus. UF202 provided voltage outputs for airflow thro ugh and gas density within the flowhead. Baseline stability for flow c hannel output (V-UF202) was <0.35% full scale (FS), and V-UF202 was li near over a range of +/-50 l/s (R(2) greater than or equal to 0.9976). Under optimal conditions, V-UF202 accuracy was determined to be +/-1. 00% FS and repeatability was +/-0.78% FS. V-UF202 resolution was 24 ml /s. The rise time for V-UF202 was 18 ms, and the -3-dB point was 18 Hz ; digital compensation provided a flat frequency response to 32 Hz. V- UF202 gain appeared to be stable over a period of 8 days. Density chan nel output (rho(UF202)) was linear over a range of 1.11-1.23 g/l (R(2) greater than or equal to 0.9645). rho(UF202) accuracy was calculated to be +/-0.50% FS, and rho(UF202) repeatability was determined to be /-0.30% FS. Resistance of the flowhead was determined to be 0.013 cmH( 2)O.l(-1).s at a flow of 40 l/s. On the basis of this study, we conclu de that UF202 should facilitate accurate measurement of breath-by-brea th airflow of exercising horses.