Technology, Instrumentation and Engineering Applications
Technology, instrumentation and engineering applications tests how physical principles become measurement and control systems. Expect sensor selection, signal processing and system-level reasoning.
Measurement systems
A measurement system has a sensor or transducer, signal conditioning, a processor and an output. Key specifications are range, sensitivity, resolution, linearity, accuracy and precision. Resolution is the smallest detectable change; accuracy is closeness to the true value.
Sensors and transducers
A thermistor changes resistance with temperature, usually with a negative coefficient; an LDR changes resistance with light; a strain gauge changes resistance with strain; a piezoelectric sensor produces charge under pressure. A potentiometer gives a voltage proportional to position.
Signal processing and control
An operational amplifier can amplify, buffer or compare. An ADC converts an analogue voltage to a digital number; an n-bit ADC with reference V_ref has a step of V_ref/2ⁿ. Control systems compare a set point with feedback and act to reduce error; open-loop systems lack feedback.
Worked example
A 10-bit ADC has a 5.0 V reference. Number of levels = 2¹⁰ = 1024, so resolution = 5.0/1024 = 4.88 mV. A reading of 512 corresponds to about 2.50 V.
Traps
Confusing resolution with accuracy, ignoring the loading effect of a meter, and forgetting that a buffer amplifier is needed to match a high-impedance sensor to a low-impedance load.