Quiz: Sensors and Measurement Chains — 10 questions

1. What does a sensor typically produce when it detects a non-electrical physical phenomenon?

A. A chemical substance such as a reagent or catalyst

B. A mechanical movement such as rotation or displacement

C. An electrical quantity such as a current or voltage

D. A change in temperature without an electrical output

Answer: (C)

Explanation

A sensor represents a non-electrical phenomenon as an electrical quantity, commonly a current or voltage. A mechanical output is more characteristic of an actuator, while chemical or thermal changes do not define the sensor’s usual output.

2. A device detects acoustic pressure and outputs a voltage, but another device receives a voltage and produces mechanical motion. How should these devices be classified?

A. The first is an actuator, and the second is a sensor

B. The first is a sensor, and the second is an actuator

C. Both devices are actuators because both produce measurable effects

D. Both devices are sensors because both involve physical quantities

Answer: (B)

Explanation

A transducer functions as a sensor when it converts a measurable physical quantity into an electrical signal, and as an actuator when it converts an electrical signal into motion. The direction of energy conversion distinguishes the two roles.

3. What best defines a measurement chain?

A. A transmission cable that carries an electrical signal between devices

B. A single sensor placed in direct contact with a physical phenomenon

C. A display unit that presents a previously processed measurement

D. A set of devices or operations used to detect a physical quantity

Answer: (D)

Explanation

A measurement chain consists of devices or operations that work together to detect a physical quantity. A sensor is merely the first element in direct contact with the phenomenon, not the entire chain.

4. Which sequence best represents the operation of a typical measurement chain?

A. Condition, process, store, acquire, transmit, then digitize

B. Transmit, display, process, acquire, digitize, then condition

C. Acquire, condition, transmit, digitize, process, then display or store

D. Display, digitize, acquire, transmit, condition, then process

Answer: (C)

Explanation

A typical chain first acquires the quantity with a sensor, then conditions, transmits, digitizes, processes, and finally displays or stores the result. Transmission carries the signal, whereas analog-to-digital conversion changes its format.

5. What is the primary function of a sensor in an electronic measurement system?

A. A component that stores electrical energy

B. A device that transmits signals wirelessly

C. A device that converts a physical phenomenon into an electrical quantity

D. A component that amplifies electrical signals

Answer: (C)

Explanation

A sensor's main role is to convert a non-electrical physical phenomenon into an electrical signal, such as current or voltage. An actuator, in contrast, converts electrical energy into another form of energy, like mechanical motion.

6. What is the main purpose of a measurement chain in a sensing system?

A. To amplify the physical phenomenon directly into a digital signal without any intermediate steps.

B. To convert electrical signals into physical phenomena for actuation purposes.

C. To generate electrical energy from a physical phenomenon for direct use in control systems.

D. To acquire, condition, transmit, convert, process, and display or store the signal from a sensor.

Answer: (D)

Explanation

The measurement chain's primary role is to acquire the physical quantity, condition the signal, transmit it, convert it into digital form, process it, and then display or store the result. This sequence ensures accurate and usable measurement data.

7. When was the piezoelectric effect first experimentally demonstrated by Pierre and Paul-Jacques Curie?

A. 1850

B. 1900

C. 1875

D. 1880

Answer: (D)

Explanation

The piezoelectric effect was first demonstrated in 1880 by Pierre and Paul-Jacques Curie. This discovery was crucial for understanding how mechanical stress can generate electrical charges in certain materials.

8. How do the thermoelectric and piezoelectric effects differ in their response to stimuli?

A. Both effects produce a voltage in response to temperature changes, but only the thermoelectric effect involves dissimilar metals.

B. The thermoelectric effect responds to temperature differences, producing a voltage, while the piezoelectric effect responds to mechanical stress, generating charges or voltage.

C. The thermoelectric effect is based on magnetic properties, while the piezoelectric effect is based on electrical polarization.

D. The thermoelectric effect generates charges when mechanical stress is applied, whereas the piezoelectric effect produces a voltage due to temperature changes.

Answer: (B)

Explanation

The thermoelectric effect produces a voltage based on temperature differences between junctions of dissimilar metals, whereas the piezoelectric effect generates charges or voltage when mechanical stress deforms certain materials. The distractor incorrectly associates the thermoelectric effect with mechanical stress.

9. Who is credited with experimentally demonstrating the piezoelectric effect in 1880?

A. Heinrich Hertz

B. Michael Faraday

C. Pierre and Paul-Jacques Curie

D. Antoine Becquerel and Alexandre Edmond

Answer: (C)

Explanation

Pierre and Paul-Jacques Curie are credited with experimentally demonstrating the piezoelectric effect in 1880. Heinrich Hertz discovered the photoelectric effect, while Becquerel and Edmond studied the photovoltaic effect; Faraday is known for electromagnetic induction.

10. What is the primary cause that enables active sensors to generate an electrical signal in response to a physical phenomenon?

A. They rely on passive components that change their electrical properties without energy conversion.

B. They measure the resistance, capacitance, or inductance variations directly.

C. They convert the energy of the measurand into electrical energy through a physical effect.

D. They detect variations in impedance caused by physical changes.

Answer: (C)

Explanation

Active sensors generate an electrical signal by converting the energy associated with the physical phenomenon into electrical energy through a specific physical effect. Unlike passive sensors, which detect variations in impedance, active sensors actively produce electrical signals as a result of energy conversion.