This chapter explores the classification, mechanisms, and metrological characteristics of various measuring transducers and sensors, crucial for different physical measurements such as displacement, force, pressure, and temperature. Different types of measurement transducers, including analog, analog-to-digital, and digital-to-analog, are examined, as well as sensor classifications based on physical phenomena, such as capacitive, inductive, and electromagnetic sensors. The chapter delves into the operational principles, applications, and measurement circuits of sensors like resistive, thermoresistive, thermoanemometers, piezoelectric, Hall-effect, ChemFETs, and fiber optic sensors. The significance of operational amplifiers (OAs) in measuring circuits is discussed, focusing on their ideal characteristics, practical circuits, and error analysis. By highlighting the detailed functionality and application of various sensors and OAs in electronic circuits, the chapter offers valuable insights for their use in diverse scientific and industrial contexts, emphasizing accuracy, signal conversion, and error mitigation.