Sensor Device, Speed Reducer, Traveling Unit For Crawler, Fluid Valve, Fluid Cylinder, Fluid Pump, Fluid Compressor, Electric Motor, Electric Actuator, Construction, Method Executed by Sensor Device, Sensor System, and Nomenclature Plate

A sensor device is attached to, for example, a mechanical component. The sensor device includes a sensor unit, an output unit, and an energy harvesting unit. The sensor unit measures a condition related to the mechanical component. The output unit outputs information that is based on the measurement result from the sensor unit to the outside. The energy harvesting unit converts energy that exists in an external environment into electric power and supplies an electric power for operating at least one of the sensor unit and the output unit.