Sensor Technologies and Biological Sensing Lecture Notes PDF

Sensor Technologies and Biological Sensing: Lecture 1 Notes January 8, 2025 1 Measurement Principles Measurement: The process of comparing an unknown quantity with a standard or related quantities. Example: Measuring time and dist...

Sensor Technologies and Biological Sensing: Lecture 1 Notes January 8, 2025 1 Measurement Principles Measurement: The process of comparing an unknown quantity with a standard or related quantities. Example: Measuring time and distance to calculate velocity. Methods: Direct: Unknown quantity directly compared to a standard. Indirect: Uses a system to indirectly compare against a standard. 2 Definitions and Classifications 2.1 Transducers and Sensors Transducer: Converts energy from one form to another. Sensor: A transducer that detects characteristics of its environment and outputs a signal. 2.2 Sensor Types Direct Sensors: Converts a stimulus directly to an electrical signal (e.g., photo- diode). Hybrid Sensors: Requires a transducer before generating output (e.g., chemical sensors). 1 2.3 Sensor Classifications Passive: Generates signal without external power (e.g., thermocouple). Active: Requires external power for operation (e.g., thermistor). Absolute: Measures stimulus against an absolute scale (e.g., absolute pressure sensor). Relative: Output depends on specific conditions (e.g., thermocouple). 2.4 Specifications and Properties Key Properties: Sensitivity, stability, resolution, accuracy, speed of response, etc. Materials: Inorganic, organic, biologic substances. Fields of Application: Civil engineering, health, environment, etc. 3 Sensor Transfer Functions Definition: Relation between stimulus (s) and output (E): E = f (s). Linear: E = A + Bs Non-linear: Examples include logarithmic, exponential, and power functions. Multidimensional Functions: Transfer functions depending on multiple variables (e.g., humidity and temperature). 4 Calibration and Error Calibration: Align sensor output with known standards. Methods: Curve fitting, system adjustment, property modification. Calibration Error: Systematic inaccuracies present in factory-calibrated sensors. 5 Sensor Characteristics 5.1 Static Characteristics Accuracy: Closeness to true value. Resolution: Minimum detectable input change. Precision: Repeatability of measurements. 2  Sensitivity: Slope of the calibration curve. Linearity: Closeness of output to a straight line. Hysteresis: Dependence on the trajectory of measurement. 5.2 Dynamic Characteristics Sensor response to time-varying inputs. Influenced by energy-storing elements (e.g., masses, inductances). 6 Reliability Definition: The probability of functioning without failure under stated conditions for a specified time. 7 Summary Key questions: What are the principles of measurement? How are sensors classified? What are calibration methods and errors? What are static and dynamic characteristics of sensors? 3