The aim of this study was to verify the concurrent validity and the biological error-free reliability of a novel low-cost commercial encoder (Ergonauta I). Validity protocol involved comparisons with a custom system and other encoder commercially available (Vitruve). Reliability protocols involved interdevices and interunit comparisons. No participants were recruited, and reliability assessments were performed in a Smith Machine by bar free fall tests. Our results showed a significant bias for mean velocity (MV) estimated by both encoders only in one of the four conditions investigated (bias = 0.05 m/s). Regarding sensitivity, the smallest detectable change suggests only values higher than 0.03 m/s must to be considered as real changes in performance, when monitoring MV and mean propulsive velocity (MPV) through Ergonauta I and Vitruve. Between-days intra-device reliability showed Ergonauta I remains highly reliable after one week for most assessments, whereas slightly less sensitive for peak velocity and peak power output.