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Transducer and sensor are the devices used to detect physical changes in the surrounding or in the electronic equipment. Though they are used for the same purpose, the transducer and sensor are different from each other. In physics, one important distinction between a sensor and a transducer is that the sensor detects physical changes in the environment, whereas the transducer translates physical quantities or non-electrical signals into electrical signals.
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Key Terms: Transducer, Sensor, Electrical Signals, Transduction, Mercury, Electrical Circuit, Energy, Transformer, Voltage, Electronic equipment
What is a Transducer?
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A transducer is a device that transforms one type of energy into another. An electrical transducer, on the other hand, transforms alternative forms of energy into electrical signals. This process of converting energy by a transducer is known as transduction.
The two components of a transducer are:
- a sensor, and
- a signal conditioning unit
The sensor senses any changes in the physical surroundings and generates a non-electrical signal. The signal conditioning device turns the signal into an electrical signal and amplifies, attenuates, or processes it to make it readable.
Steps of Transducer Working
An example of a transducer is a pressure transducer. It converts applied pressure or stress into an electrical signal. It consists of two oppositely charged plates, one of which is fixed and the other of which is moveable. When pressure is applied to the moving plate, the capacitance in-between fluctuates. The applied voltage fluctuates with changes in capacitance. In this way, the pressure is converted into an electrical signal.
Transducer
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Features of a Transducer
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Some important features of a transducer are as follows:
- Accuracy - It is defined as how close a reading gets to matching an approved standard value, ideal value, or real value of the variable being measured.
- Linearity - The transducer's output should be linearly proportional to the amount being measured. Its input-output characteristic should be linear.
- High output - The output signal from the transducer should be relatively high so that it may be readily processed and monitored. The output must be significantly more than the noise. In many applications, nowadays, digital output is desired.
- Repeatability - When the same quantity is supplied to the input repeatedly, the transducer's output must be exactly the same, under the same environmental circumstances.
- Ruggedness - To endure overloads, the transducer should be mechanically tough. Overload protection should be included.
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What is a Sensor?
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A sensor is a device that monitors environmental input and responds to them in the form of signals. Light, heat, motion, moisture, pressure, or any other environmental phenomena might constitute the specific input. In a sensor, the output signal is not always in a readable format. It is further amplified, attenuated, or converted into a readable signal using an electrical circuit.
Steps of Sensor Working
The mercury in a thermometer is an example of a sensor. Mercury is a liquid metal used to detect changes in temperature. It expands as the temperature rises. However, until it is placed in a proper scale, it is unreadable. Similarly, the resistance of a thermistor fluctuates as the temperature changes.
An Oxygen Sensor
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Features of a Sensor
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Some important features of a sensor include:
- Accuracy - It indicates how close the sensor's output is to the predicted value. For a particular input, the sensor's output value is related to how near it is to the predicted output value.
- Linearity - It illustrates the link between input and output changes. Any change in input at any level within the range will yield the same change in output in a sensor with linear output.
- Range - It is the difference between a sensor's smallest and greatest outputs or the difference between the smallest and largest inputs with which it can function effectively.
- Repeatability - It is poor. Also, because the performance of the device is dependent on sensors, a specified range is necessary for operational performance. There is no compensation since repeatability is a random phenomenon.
- Sensitivity - It is calculated by dividing the change in output reaction by the change in input response. Highly sensitive sensors exhibit higher output variations as a result of input fluctuations.
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Difference Between Transducer and Sensor
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The key differences between a transducer and a sensor are tabulated below:
| Transducer | Sensor |
|---|---|
| Transducers convert energy from one form to another form. | Sensors convert physical parameters to electrical output. |
| All sensors are not transducers. | All transducers contain a sensor. |
| When joined in a bridge circuit, they function as transducers. | When it responds to a stimulus, it is referred to as a sensor. |
| It distributes power in the same or different forms from one system to another. | It recognizes and converts changes in physical stimuli into a signal. |
| Transducer is used for sensing elements and also for circuitry. | Sensor is used for sensing the element itself. |
| Examples are - Piezoelectric transducer, strain gauge. | Examples are - Temperature sensors, proximity sensors. |
Things to Remember
- A sensor detects changes in the physical quantities in its environment, whereas a transducer transforms one form of energy into another by the process of transduction.
- A sensor does not necessarily have a transducer, but a transducer must always have a sensor.
- A sensor's output may or may not be an electrical signal, whereas a transducer's output is an electrical signal.
- A sensor is a component in and of itself, but a transducer includes a sensor as well as a signal conditioning device.
- A sensor cannot be directly linked to other systems, although a transducer can.
- A sensor produces an analog output signal in real-time, but a transducer may produce both analog and digital electrical signals.
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Sample Questions
Ques. How to calculate the sensitivity of the transducer? (1 Mark)
Ans. The transducer sensitivity is determined by dividing the transducer range by the full-range output.
Ques. What are the applications of transducers? (5 Marks)
Ans. Some applications of transducers are -
- It is used to measure the load on an engine.
- They are used in the process of acceleromyography, i.e, to detect the movement of muscles.
- They have an application in ultrasound machines.
- They are used in speakers to convert electrical signals into acoustic sound.
- They are also used in antennas.
Ques. What are the different types of transducers? (5 Marks)
Ans. Transducers are classified into different types depending upon their characteristics:
- Classification based on Power Source
- Active Transducer - It does not require an external power source.
- Passive Transducer - It requires an external power source.
- Classification based on Output Conversion
- Primary Transducer - It converts physical quantity into mechanical signal.
- Secondary Transducer - It converts mechanical signal into electrical signal.
Apart from this, the other two types are called - Transducer and Inverse Transducer.
A transducer converts any form of energy into an electrical signal, whereas, an inverse transducer converts electrical energy into other forms of energy.
Ques. What is an inductance transducer? (2 Marks)
Ans. A set of significant devices that may be used in a variety of applications is transducers based on inductance variation. When the amount to be measured changes, the self-inductance or mutuality of a couple of coils changes in these transducers.
Ques. What are the different types of sensors? (3 Marks)
Ans. The different types of sensors are:
- Temperature sensor
- Speed sensor
- Sensor that detects ultrasonic waves
- Sensor based on pyroelectricity
Ques. Give applications of different types of sensors. (3 Marks)
Ans. The following are some examples of sensor applications:
- The pressure of gas and liquids is measured using pressure sensors.
- Humidity sensors detect relative humidity, which is used to measure both air temperature and moisture.
Ques. How does the inductive proximity sensor work? (3 Marks)
Ans. It allows us to detect the presence of metallic items without having to touch them. Because of their high-speed switching and tiny size, they are used in automation applications. It is made up of an oscillator-driven coil that generates an electromagnetic field at the sensor's active face. The electromagnetic field is reduced when a metal target enters this region. As a result, the sensor switch activates or deactivates. Sensing the presence of metallic elements such as screws and monitoring the rotational speed of axial detecting cams are two examples of inducing sensor applications.
Ques. What is a linear potentiometer transducer, and how does it work? (5 Marks)
Ans. A linear potentiometer transducer is made up of a short-circuiting potentiometer and a slider. It works in the following manner:
- The opposite end of the slider is connected to a slider arm.
- The force summation mechanism on the slider arm causes linear displacement of the slider. It results in a short circuit in the resistance of a segment of the potentiometer.
- Make all of the resistance settings ABC on the potentiometer. Allow the slider to go to the BC setting for the resistance. The amount of resistance increases when the slider is dragged further to the right.
- The rise in resistance value causes a corresponding change in the linear displacement of the slider.
- To calculate the resistance change, a wheatstone bridge can be employed.
Ques. What are displacement transducers and how do they work? (5 Marks)
Ans. An electromechanical device that transforms mechanical motion or vibrations, especially rectilinear motion, into a variable electrical current, voltage, or electric signals, and vice versa is known as displacement transducer. Actuating mechanisms are commonly used in automatic control systems or as mechanical motion sensors in measuring technologies.
To measure linear position, a displacement transducer, also known as a DT, is utilized. Linear displacement is the movement of an object in one direction along a single axis. Measuring displacement indicates the direction of motion. The linear displacement sensor's output signal can be negative or positive and measures the distance an item has moved in millimeters (mm) or inches (in).
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