Industrial Measurements MSBT third year

Unit 1
Industrial Measurements notes

1. IME

2. What is a Transducer? A transducer is a device that converts one form of energy into another, such as converting mechanical energy into electrical signals. Examples of a Transducer Thermocouple:  A thermocouple is a transducer commonly used for temperature measurement. Thermocouples are widely employed in industries, laboratories, and HVAC systems for temperature monitoring and control. Microphones:  Microphones are another familiar example of transducers. They convert sound waves traveling through the air into electrical signals. These electrical signals can then be amplified, recorded, or transmitted for various applications, including audio recording, public address systems, telecommunication, and more.

3. What is a Sensor? A sensor is a device that detects and responds to a specific input, such as light, temperature, pressure, or motion and converts it into a measurable output. -Sensor is used for feedback purposes in the machine. -Sensor is used for monitoring and control in the machine. -Sensor is used for safety and security in the machine. -Sensor is used for predictive maintenance and energy efficiency in the machine. Sensor is a device that detects changes in physical, electrical, or chemical properties and produces an electrical output in response to that change. Examples of a Sensor Barometer: A barometer is a sensor used to measure atmospheric pressure. It detects the changes in air pressure caused by weather conditions and converts them into electrical signals. These signals can then be interpreted to determine whether the pressure rises or falls, providing valuable information for weather forecasting, aviation, and meteorological applications. Accelerometer: An accelerometer is a sensor that measures acceleration or changes in velocity. It is commonly used in smartphones, gaming controllers, and vehicle stability systems.  Accelerometers  detect linear acceleration and tilt in multiple directions and convert them into electrical signals. This enables the detection of motion, orientation, and vibration, allowing for applications like screen rotation, gesture recognition, and impact detection.

4. What is the main difference between a transducer and a sensor? The main difference between a transducer and a sensor lies in their primary functions: a transducer focuses on converting one form of energy into another, while a sensor concentrates on detecting and measuring a specific input.

5. D ifference between a transducer and a sensor T ransducer A microphone is a typical example of a transducer. It converts sound waves into electrical signals that can be amplified, recorded, or transmitted. S ensor An accelerometer, which measures acceleration, is a type of sensor. It detects the changes in acceleration and converts them into electrical signals for further analysis.

6. Proximity Sensors . "Proximity Sensors" are sensors that detect the movement or presence of an object without making physical contact with the object and convert that information captured into an electrical signal. There are three types of Proximity sensors: Each type of proximity sensor senses an object in its distinct ways. Inductive Proximity Sensors- systems that use the eddy currents that are generated in metallic sensing objects by electromagnetic induction, Capacitive Proximity Sensors- systems that detect changes in electrical capacity when approaching the sensing object, and Magnetic Proximity Sensor- systems that use magnets and reed switches.

7. Working Principle of Capacitive Proximity Sensor Capacitive Proximity sensors are based on parallel plate capacitors. Parallel Plate Capacitor consists of two parallel plates that are separated by a dielectric material which is a poor conductor of electricity such as plastic, glass, or porcelain. The two parallel plates are conductive and they are usually made of Aluminum, Tantalum, or other metals. A metal plate typically has an equal amount of positively and negatively charged particles, which means it is electrically neutral. If we connect a power source or a battery to the capacitor, a large number of electrons start moving from the negative terminal of the battery through the conductive wire.

8. Working Principle of Capacitive Proximity Sensor when these electrons reach the right side plate of the capacitor, the dielectric material will strongly oppose the movement of electrons from the right side plate to the left side plate. as a result number of electrons that is the negative charge carriers on the right side plate of the capacitor will be higher than the number of protons, that is the positive charge carriers. Due to this the right side plate of the capacitor becomes negatively charged at the same time the electrons on the left side plate experience a strong attractive force from the positive terminal of the battery. As a result,  the electrons leave from the left side plate and will be attracted towards the positive terminal of the battery. Due to this the number of protons will be higher than the number of electrons in the left side plate and as a result, the left side plate of the capacitor becomes positively charged. This is how the charging of the capacitor takes place. The right side plate has now developed a net negative charge and the left side plate has developed an equal net positive charge. this creates an electric field with an attractive force between them which holds the charge of the capacitor.

9. Capacitance and Dielectric Constant The ability of a capacitor to store electric charge when a voltage is applied is called capacitance. The quantity measuring the ability of a dielectric material to store charge is called the dielectric constant.

10. Types of Capacitive Proximity Sensors

11. Dielectric Type of Capacitive Proximity Sensors Dielectric type of capacitive proximity sensor can detect any target that has a dielectric constant greater than air. It has two parallel plates inside the sensing head which operates like an open capacitor. Here air acts as the dielectric . when no target is present the capacitance between the plates will be very less. These plates are linked to an oscillator and a detector circuit. As the target which has a dielectric constant more than air comes near to the sensor the capacitance between the plates increases. An increase in capacitance increases the amplitude of the oscillation of the oscillator. when the oscillation exceeds a specific value, the detector turns on the output of the sensor.

12. Dielectric Type of Capacitive Proximity Sensors when the target object moves away from the sensor the oscillation amplitude decreases and when it falls below a threshold value the sensor returns to the initial state. Dielectric type capacitive proximity sensors  will sense both metallic and non-metallic objects.

13. Conductive Type of Capacity Proximity Sensor In conductive type capacitive proximity sensor there is only one capacitor plate inside the sensor. T he target itself becomes the other plate of the parallel plate capacitor. The plates of a parallel plate capacitor should be conductive, so this type of sensor is used if the target is an electrically conductive material. The air gap between the sensor and the target functions as the dielectric. The plate inside the sensor is connected to an oscillator circuit that is used to generate an electrostatic field.

14. Conductive Type of Capacity Proximity Sensor As the conductive target approaches the sensor, the distance between the two plates decreases due to which the capacitance increases and results in increase of oscillation amplitude.  once the oscillations exceed a predetermined value, the output signal from the sensor is generated which indicates that the target has reached near the sensor.

15. Inductive Proximity Sensors Inductive proximity sensors are used to detect metal targets. An inductive proximity sensor has four main components. 1. Coil- the coil generates the necessary electromagnetic field a cup-shaped magnetic core holds the coil. This core is necessary to concentrate the coil's magnetic field on the front area of the sensor. 2. O scillator- The oscillator is generally an LC oscillator. I t produces radio frequency which helps to generate an electromagnetic field. 3.  the trigger circuit- The trigger circuit senses the change in amplitude of oscillation and gives the signal to the output circuit. 4. output circuit-The output circuit has a transistor after receiving the signal, the transistor switches on and gives an output.

16. Working Principle of Inductive Proximity Sensors Inductive proximity sensors operate based on Faraday's law of Inductance.   According to Faraday's law of Induction, when an electrically conducting object is placed in a time-varying magnetic field, an electric current called an Eddy current will be generated in the object. According to Len's law, the Eddy current creates a magnetic field in a conductor and this eddy current magnetic field opposes the magnetic field which created it.

17. Working Principle of Inductive Proximity Sensors The proximity sensor is installed in the area where we need to sense the presence of an electrically conductive target object. when the sensing coil in the oscillation circuit is supplied with an alternating current, a changing magnetic field is created around the coil. when the target object enters into this electromagnetic field some of the electromagnetic energy is transferred to the object. According to Faraday's law of Induction an electric current called Eddy current will be generated in the object. This eddy current produces another magnetic field called Eddy current magnetic field and it opposes the magnetic field which created it.

18. Working Principle of Inductive Proximity Sensors As the eddy  current magnetic field opposes the magnetic field of the coil, the intensity of the magnetic field of  the coil reduces As the target comes very close to the sensor, the eddy current increases and decreases the amplitude of the electromagnetic field. The trigger circuit monitors the amplitude and when the amplitude goes below a predetermined level the output state of the sensor switches from its normal condition. As the target moves away from the sensor the amplitude of the electromagnetic field increases and at a predetermined level the trigger switches the output state of the sensor back to its normal condition.

19. Features of Proximity Sensor Proximity Sensors detect an object without touching it, and they therefore do not cause abrasion or damage to the object. Devices such as limit switches detect an object by contacting it, but Proximity Sensors can detect the presence of the object electrically, without having to touch it. No contacts are used for output, so the Sensor has a longer service life (excluding sensors that use magnets). Proximity Sensors use semiconductor outputs, so there are no contacts to affect the service life. Proximity Sensors provide high-speed response, compared with switches that require physical contact. Proximity Sensors can be used in a wide temperature range. Proximity Sensors can be used in temperatures ranging from −40 to 200°C.

20. Features of Proximity Sensor Proximity Sensors are not affected by colors. Proximity Sensors detect the physical changes of an object, so they are almost completely unaffected by the object's surface color. Unlike switches, which rely on physical contact, Proximity Sensors are affected by ambient temperatures, surrounding objects, and other Sensors.

21. Optical sensor An optical sensor converts light energy into electrical signals. We all have experienced that smartphones, laptops, LCD screen need to sense the amount of ambient light and maintain the brightness on screen to match with ambient light. Optical sensors detect and measure light intensity, converting light rays into electrical signals. The sensor is connected to an electrical trigger sensitive to light changes. Optical sensors are applied in many devices, including computers and motion detectors. Light Energy Optical Sensor Electrical energy

22. Working Principle of Optical Sensor Optical sensors are mainly a non-contact sensing technology that detect variations in light energy   and produce a resultant electrical signal or change in conductivity. The method of sensing light rays is known as optical sensing. The sensor type used for optical sensing is known as an optical sensor.

23. Working Principle of Optical Sensor In general, there are two components in optical sensing viz. transmitter (i.e. optical source) and receiver (optical detector). As shown light beam changes its parameters when any object comes between the transmitter and receiver. Five useful parameters of light are being measured in optical sensing viz. intensity, phase, wavelength, polarization, and spectral distribution. T he following physical and chemical measurements can be measured due to the advent of optical sensing technology. They are • Temperature, • flow, • pressure, • displacement, • liquid level, •  vibration, • rotation, • acceleration, • magnetic fields, •  force, • Ph, • radiation, • chemical species, •  humidity, • strain, • electric fields, • velocity, • acoustic field etc.

24. Applications of Optical Sensing Following are the applications of optical sensors: • It is used in remote sensing satellites. • Used in imaging • Quality and Process Control applications • Metrology • Medical instruments

25. Advantages of Optical Sensors The optical signal is immune to electromagnetic interference and hence it is ideal to be employed in a microwave environment. It has very high sensitivity, range, and resolution compared to non-optical sensors. It has a wider dynamic range.  It is used in an explosive environment.  It is small in size and light in weight. It is resistant to high temperatures and chemically reactive environments. Hence optical sensors are ideal for harsh environments. It can be used to monitor a wide range of physical as well as chemical parameters. It provides complete electrical insulation from high electrostatic potential.

26. Disadvantages of Optical Sensors The only problem with both optical sensors and non-optical sensors is interference from multiple effects. For example, the sensor used for pressure/strain measurement is very sensitive to temperature variation. Research is in progress to study and find out ways to distinguish between these different effects to have accurate measurements in optical sensing. The other concern different types of losses involved in the optical domain are absorption loss, impurity loss etc.

27. Transducer Electronic instrumentation system - it consists of several components that do the measurements and give their output as the results of the measurements. in an instrumentation system we have those components that are doing the measurement. Input Output Measuring Device