23. An actuator is a device that: a) changes AC to DC b) changes DC to AC c) converts an electrical signal into mechanical movement d) converts mechanical movement into an electrical signal 24. For a thermocouple to generate a voltage, a temperature difference must exist between the (a) and (b)_junctions. 25 The sensor illustrated in Figure is a: a) thermocouple b) turbine flow meter c) strain gauge load cell d) retroreflective sensor - n f