A programmable electrically braked ergometer

Abstract

Research protocols require that the actual braking power (Wb) of electrically braked ergometers (EBE) is precisely set at the chosen power level, stable, and universally programmable. No commercially available EBEs appear to meet jointly the above conditions. In fact, EBE settings were found to deviate up to 25% from the reference level (WR), their Wb to drop as a result of increased temperature as much as 30% within 1 h of continuous operation, and the programming features to be limited and rigid. To overcome the above pitfalls a procedure for building or improving EBEs is presented whereby 1) the stator of the brake used as a dynamometer is mounted on ball bearings, the torque being transmitted to a strain gauge; 2) the number of revolutions of the rotor is measured on a cogwheel by a proximity detector and an impulse counter; and 3) the torque and impulse number signals are fed into a low-priced microcomputer controlling the brake's power supply. The device has proved to be satisfactory in following any preprogrammed exercise-forcing functions. In the range approximately 10-500 W, Wb = WR +/- 1%.