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Engineering
Grade 9-12
Industrial Sensors Reference Cheat Sheet
A printable reference covering proximity sensors, encoders, temperature sensors, pressure sensors, calibration, accuracy, and signal types for grades 9-12.
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Industrial sensors help machines measure position, motion, temperature, pressure, flow, and other physical conditions. This cheat sheet gives students a quick reference for common sensor types used in manufacturing, robotics, automation, and control systems. It is useful for comparing sensor outputs, choosing the right device, and understanding how measurements become electrical signals.
Key Facts
- A proximity sensor detects nearby objects without physical contact, and common types include inductive, capacitive, ultrasonic, and photoelectric sensors.
- An inductive proximity sensor detects metal objects using an electromagnetic field, while a capacitive proximity sensor can detect many materials by sensing changes in capacitance.
- A digital sensor output is usually ON or OFF, while an analog sensor output changes continuously, such as 0 to 10 V or 4 to 20 mA.
- Sensor span equals maximum input value minus minimum input value, so span = max range - min range.
- Measurement error can be calculated as error = measured value - true value.
- Percent error can be calculated as percent error = absolute error / true value x 100%.
- Resolution is the smallest change a sensor can detect, and higher resolution means smaller changes can be measured.
- For a linear sensor, output can often be modeled by output = slope x input + offset.
Vocabulary
- Sensor
- A device that detects a physical condition and converts it into an electrical signal or readable output.
- Proximity Sensor
- A sensor that detects whether an object is nearby without needing direct contact.
- Encoder
- A sensor that measures position, speed, or direction of a rotating or moving part.
- Calibration
- The process of comparing and adjusting a sensor so its output matches a known standard.
- Accuracy
- How close a sensor reading is to the true or accepted value.
- Resolution
- The smallest change in input that a sensor can reliably detect.
Common Mistakes to Avoid
- Confusing accuracy with resolution is wrong because a sensor can show very small changes but still be far from the true value.
- Using the wrong sensor type for the material is wrong because inductive sensors detect metal well, but they are not the best choice for plastic, glass, or liquid targets.
- Ignoring the sensor range is wrong because readings outside the rated range may be clipped, unstable, or inaccurate.
- Mixing up analog and digital outputs is wrong because an analog output gives changing values, while a digital output only switches between states such as ON and OFF.
- Skipping calibration is wrong because sensors can drift over time, causing the machine to make decisions from incorrect measurements.
Practice Questions
- 1 A pressure sensor has a range from 0 psi to 200 psi. What is its span?
- 2 A temperature sensor reads 76 degrees C when the true temperature is 80 degrees C. What is the measurement error?
- 3 A level sensor has a true value of 50 cm and an absolute error of 2 cm. What is the percent error?
- 4 A robot must detect both metal brackets and plastic bins on a conveyor. Which sensor type would be more flexible than an inductive proximity sensor, and why?