Industrial Sensors and Actuators Quiz

Study Notes

Sensing elements translate physical signals like temperature, pressure, or displacement into electrical or pneumatic information for analysis, decision-making, and control input calculation.
Actuation elements convert computed control inputs (electrical or pneumatic information) into physical process inputs like heat, force, or flow rate to effect desired changes in process outputs.

Modern industrial systems use diverse sensors of different sizes, weights, costs, complexities, and technologies.
All sensors consist of functional elements connected in a specified way to provide signals in a specific form for various automation tasks.

Actuators convert control system output signals into forms applicable to the actual process, producing desired variations in physical variables.
They convert controller output (information without power, in the form of electrical voltages or pneumatic pressure) into appropriate physical variables (like torque, heat, or flow).
Actuators amplify the energy level of the signal to cause changes in process variables.
Actuators are high-powered devices, unlike sensors.
Actuators often produce motion from electrical signals, which is then converted to other forms.

Day-to-day life: ATMs, vehicle starting, automatic washing machines, electrically driven pumps, UPS systems.
Industry: Painting robots in the automobile industry, soldering machines, DCS (Distributed Control Systems), SCADA (Supervisory Control and Data Acquisition).

Computer and electronics (HMI)
Communication using TCP/IP (Transmission Control Protocol/Internet Protocol) for server communication.
Sensors: Magnetic sensors to read card data, cameras, timers.
Electromechanical solenoids and actuators for accurate currency counting and dispensing.
Printers for printing transactions.

Industrial automation systems are complex, involving numerous devices and technologies working synchronously.
Understanding the different parts of the system is essential for evaluating its performance.

Pros: Non-contact, no moving parts, small size, fast switching, no switch bounce, insensitive to vibration and shock, and various configurations available.
Cons: Requires alignment, susceptible to ambient light conditions (like welding), needs a clean, dust and water-free environment.

These sensors emit ultrasonic sound waves and measure the time it takes for the waves to return, indicating the distance to an object.

They measure force or pressure applied to the sensor.
Common mechanisms include:
- Physical motion and measurement using LVDTs (Linear Variable Differential Transformers).
- Strain gauges (metal that changes resistance under stress).
- Piezoelectric materials that generate current when deformed.

Based on the thermoelectric effect discovered by Thomas Johann Seebeck in 1821.
A voltage is generated in a conductor when subjected to a temperature gradient.
A thermocouple is formed when two dissimilar metals are in contact at one end, and voltage is measured between the other ends.

### Sensor Characteristic Curves

Different sensor types have different relationships between the measured variable and the output signal.
Graphs illustrate these relationships and are used for calibration and analysis.

### Example Sensor Characteristic Curves

Shown are the curves for a thermocouple, an RTD (Resistance Temperature Detector), and a thermistor.
Each curve shows the output signal (voltage or resistance) plotted against temperature.
The curves demonstrate that different sensors have different sensitivities and ranges.