A fluid level sensor (160) measures fluid level in a container (220) containing fluid displaced by movement of a driving mechanism (120). The fluid level sensor comprises: at least one energy source (55)； at least one energy detector (555) to detect energy emitted by the at least one energy source (55), the at least one energy detector (555) further configured to generate a signal to be processed by a processor； and a regulator to regulate the level of energy received by the at least one energy detector (555) based, at least in part, on the fluid level in the container (220).
