Chapter 2 Sensors and Signal Conditioning PDF

Chapter 2 Sensors and Signal Conditioning SFE3043 Computer Programming and Interfacing by Dr Mohd Norzaidi Mat Nawi Content Outline Sensors Introduction Transducer vs Sensors Transducer Classification Commonly Detectable Phenomena Measurable Quantities S...

Chapter 2 Sensors and Signal Conditioning SFE3043 Computer Programming and Interfacing by Dr Mohd Norzaidi Mat Nawi Content Outline Sensors Introduction Transducer vs Sensors Transducer Classification Commonly Detectable Phenomena Measurable Quantities Sensor Classifications Choosing a Sensor Technical Datasheets Introduction 1 What are Sensors? Devices that detect and respond to physical phenomena (e.g. temperature, light and motion) and convert into measurable electrical signal 2 Important of Sensors Critical in various field such as healthcare, automotive, environmental monitoring and smart technology 3 Imagine a world without a sensors? Sensors Today! Transducers vs. Sensors Sensors are typically categorized as transducers, but not all transducers are sensors. While sensors are designed to measure physical quantities, transducers can be used for a wider range of signal conversion purposes. Sensors Transducers Designed to measure physical Convert energy from one form to quantities. another. Output is usually electrical signals. Output can be electrical, mechanical, Focus on sensing and or other forms. measurement. Focus on energy conversion. Transducer Classifications Principle Used Analog/Digital TRANSDUCERS Passive/Active Primary/Secondary Inverse Transducer Principle Used Transducers are classified based on the physical principle used for conversion. 1 Resistive 2 Capacitive Change in resistance based Change in capacitance based on the measured variable. on the measured variable. 3 Inductive 4 Piezoelectric Change in inductance based Electric charge generated on the measured variable. due to mechanical stress. Principle Used Resistive Transducers Principle These transducers operate based on the change in resistance of a material when a physical quantity (like temperature, pressure, or displacement) is applied. Example How it Works Strain gauges - A strain gauge measures deformation (strain) of an object by When a physical phenomenon changing its electrical resistance based on the applied force or stress. affects the resistive element (e.g., a metal or semiconductor), the electrical resistance changes. This change can be measured and converted into a corresponding electrical signal. Other Example: Thermistors, Potentiometer Principle Used Capacitive Transducers Principle Capacitive transducers work on the principle of capacitance, which is the ability of a system to store charge. The capacitance changes in response to physical changes (such as displacement, pressure, or humidity). How it Works Examples These transducers consist of two Capacitive sensor- A capacitive transducer measures changes in capacitance due conductive plates separated by an to displacement or pressure. 𝜀𝑜 𝜀𝑟 𝐴 insulating material (dielectric). 𝐶= 𝑑 When a physical quantity changes 𝐶 = capacitance (in farads) the distance or area between the 𝜀 = permittivity of the dielectric material (in farads per meter) plates, the capacitance varies. This 𝐴 = area of one of the plates (in square meters) 𝑑 = distance between the plates (in meters) variation can be measured as an electrical signal Other example: Pressure Sensor (Capacitive type) Principle Used Inductive Transducers Principle Operate based on changes in inductance, which occur due to variations in magnetic fields or the position of conductive objects Examples How it Works An inductive transducer measures changes in inductance based on the position Inductive transducers work by of metallic objects. utilizing coils of wire that generate a magnetic field. When a metallic L = inductance (in henries) object approaches the coil, it 𝜇 = permeability of the core material (in henries per meter) alters the magnetic field, changing 𝑁 = number of turns of the coil 𝐴 = cross-sectional area of the coil (in square meters) the inductance of the coil. 𝑙 = length of the coil (in meters) Other examples: LVDT (Linear Variable Differential Transformer) and Inductive Flow Meters. Principle Used Piezoelectric Transducers Principle Utilize the piezoelectric effect, where certain materials generate an electrical charge in response to mechanical stress or pressure. How it Works Examples Piezoelectric transducers are Piezoelectric Sensor - Convert mechanical energy (such as pressure or made from materials that exhibit vibrations) into electrical signals. piezoelectric properties. When Microphones: Use piezoelectric materials to convert sound waves into electrical mechanical stress is applied to signals. these materials, they generate an Ultrasonic Transducers: Generate ultrasonic waves for imaging or distance electrical charge proportional to measurement. the applied stress. Analog vs. Digital Transducers Analog Transducer Analog transducers convert physical quantities (like temperature, pressure, or displacement) into continuous electrical signals Characteristics Produces a continuous signal (e.g., voltage, current). Output varies smoothly over time. Examples: Thermocouples, LVDTs (Linear Variable Differential Transformers), Strain Gauges. Analog vs. Digital Transducers Digital Transducer Digital transducers convert physical quantities into discrete signals, typically in binary form (0s and 1s). The output has distinct steps and does not vary continuously. Characteristics Produces a discrete or binary output. Signal can be transmitted easily over long distances. Common in digital systems like microcontrollers. Examples: Rotary encoders, switch, tilt sensor Active vs. Passive Transducers Active Transducer Active transducers generate their own output signal from a physical input (stimulus) without needing an external power. Example: Piezoelectric transducer How it works: A piezoelectric sensor generates an electrical charge when mechanical stress or pressure is applied to a piezoelectric material The output voltage is depends on the piezoelectric material Quarts Crystal ~ 0.23 mV Barium titanate Crystal ~ 14mV Active vs. Passive Transducers Passive Transducer Passive transducer require an external power to operate. It produce a change in passive electrical quantity such as resistance, capacitance, or inductance in response to a physical stimulus Examples: Light Dependent Resistor (LDR) Resistance changes depends on the intensity of light In the dark, an LDR has high resistance (in MΩ) In bright condition, the resistance decreases significantly (to a few Ω) Other examples: Strain gauge, Thermistor Primary vs. Secondary Transducers Primary Transducer A primary transducer directly converts the measured physical quantity into an intermediate signal. It typically consists of mechanical components that transform the physical input (such as pressure, temperature, or force) into a mechanical signal, which can then be further processed Secondary Transducer A secondary transducer converts the output from a primary transducer into a more usable form, often an electrical signal. It processes the intermediate signal provided by the primary transducer and transforms it into a measurable or readable output, such as voltage or current, for further analysis or display  Primary vs. Secondary Transducers Example Primary Transducer: Bourdon tube It converts pressure into mechanical displacement Secondary Transducer: LVDT (Linear Variable Differential Transformer) It converts the displacement into an electrical signal P=0 P>0 Inverse Transducer An inverse transducer is a device that converts an electrical signal into a physical effect, essentially performing the opposite function of a typical transducer. While standard transducers convert physical phenomena into electrical signals, inverse transducers take electrical energy and produce a physical response Examples: Electric Motor, LED, Piezoelectric actuator Activity 1: Explore the Resistive-type Sensor Air Flow Activity 1: Explore the Resistive-type Sensor Materials: Paper Based Force Sensor Paper Pencil Objectives Multimeter 1. Build a simple force sensor using common materials like paper and pencil Conductive tape and wires 2. Explore how external force affects resistance changes in the sensor Crocodile clips What happen to the resistance when force is applied? Activity 1: Explore the Resistive-type Sensor What happens? When force is applied, it stretches the graphite, changing the contact area between the graphite (A). This stretching increases the physical separation between particles, decreasing the probability for electrons to move freely. As a result, the resistance increases Casiraghi, C., Macucci, M., Parvez, K., Worsley, Wang, Y. H., Lee, C. Y., & Chiang, C. M. (2007). A Lin, CW., Zhao, Z., Kim, J. et al. Pencil Drawn Strain Gauges and R., Shin, Y., Bronte, F.,... & Fiori, G. (2018). MEMS-based air flow sensor with a free-standing Chemiresistors on Paper. Sci Rep 4, 3812 (2014). Inkjet printed 2D-crystal based strain gauges on micro-cantilever structure. Sensors, 7(10), 2389- paper. Carbon, 129, 462-467. 2401. Commonly Detectable Phenomena Temperature Pressure Light Motion Acceleration Flow Measurable Quantities Stimulus Measured Quantities Mechanical Position, Velocity, Acceleration, Force, Pressure, Torque, Strain, Stress Optical Light Intensity, Wavelength, Refractive Index, Absorption, Reflectivity Electromagnetic Magnetic Field Strength, Magnetic Flux, Inductance, Permeability Acoustic Sound Pressure, Sound Intensity, Frequency, Wave Velocity Electric Voltage, Current, Resistance, Capacitance, Charge, Conductivity, Permittivity Thermal Temperature, Heat Flow, Thermal Conductivity, Specific Heat Chemical Gas Concentration, Liquid Concentration, pH Level, Humidity Biological Biochemical Reactions, Biomolecular Concentrations  Activity 2: Exploring Smartphone Sensors Objectives: In Acoustics category Use the Phyphox app to explore various sensors on their Audio Amplitude (Sound) smartphone Open the Audio Amplitude sensor in Phyphox. Procedures Speak, or clap near the In Groups, download an install the app “Phyphox” phone and observe how the In the Phyphox app, focus on Raw sensors category: sensor captures sound Acceleration (without g): amplitude. Navigate to the accelerometer function, and try Proximity Sensor moving the phone quickly in different directions Tap the “+” button, go to Simple (X, Y and Z). Observe how acceleration is Experiments, and select measured. Proximity Sensor. Light Sensor: Hold your hand near the Open the light sensor function and cover or proximity sensor (usually expose the phone's light sensor to different light near the top of the screen) intensities. Observe the light intensity and observe the changes in measurements. distance detected by the Magnetometer: sensor. Use the magnetometer to detect nearby magnetic fields (e.g., place a magnet near the phone and observe changes). Sensor Classifications 1 Mechanical Sensors 2 Temperature Sensor 3 Acoustic Sensors Measure physical quantities like Measure temperature or heat Measure sound, vibrations or position, velocity, pressure and force related properties acoustic waves Example: Accelerometers, strain Example: Thermocouples, Example: Microphone. gauges, load cells, piezoelectric thermistor, IR thermal sensor Ultrasonic sensor sensors Optical Sensors 5 Light Sensors 6 Environmental Sensors 4 Detect the presence or absence of Detect and measure light changes Detect environmental parameters, an object nearby Example: Photodiodes, LDR humidity, soil moisture, air quality Example: Inductive proximity and more sensor, ultrasonic proximity sensor, Example: pH sensors, Gas sensor, soil IR, Photogate moisture sensor Activity 3: Guess the Sensor? Objectives: To identify a randomly assigned sensor by its model, understand how it works and discover real world applications. Procedures Each group will given an unknown sensor Research the assigned sensor and provide the following information: Sensor name: Identify the sensor based on its model. Measurable quantity: What physical quantity the sensor measures How it works: Explain the working principle of the sensor Applications: Identify the applications Each group will share their findings to the class Sensor Classifications Potentiometer (Mechanical Sensor) Working Principle A potentiometer is a variable resistor that adjusts the resistance in a circuit based on the position of its wiper or slider. It consists of a resistive element and a movable contact (wiper) that slides across this element. As the wiper moves, the resistance between the wiper and the terminals changes, providing a variable output voltage. Applications: Volume Control: Commonly used in audio equipment like radios, where rotating the potentiometer knob adjusts the volume by changing resistance and output voltage. Position Sensing: Potentiometers are used in joystick controls, servo motors, and industrial equipment to measure the position of mechanical components. Dimmer Switches: In lighting systems, potentiometers adjust the brightness of lights by controlling the amount of power sent to the light source. Tuning Circuits: Used in tuning radio receivers by adjusting the resistance to alter the frequency of a signal. Sensor Classifications Strain Gauges (Mechanical Sensor) Working Principle Strain gauges measure the amount of strain (deformation) in an object. When an external force is applied to a material, the material deforms, causing a change in its electrical resistance. Strain gauges convert this change in resistance to an electrical signal. Strain and Resistance The relationship between strain and resistance is described by the gauge factor (GF), which determines how much the resistance changes relative to the amount of strain applied. Change in Resistance: The strain causes the resistance to increase when stretched and decrease when compressed. Output Signal: The small change in resistance is typically measured by a Wheatstone bridge circuit, which amplifies the signal for accurate measurement. Sensor Classifications Strain Gauges (Mechanical Sensor) Applications Load Cells: Strain gauges are integral to load cells, which measure weight or force in applications like digital scales, industrial weighing systems, and force measurement devices. Structural Health Monitoring: Strain gauges are used to monitor stress and strain in bridges, buildings, and other structures to ensure they are safe and detect any signs of damage or failure. Aerospace and Automotive Testing: Used in the development and testing of aircraft, cars, and other vehicles to measure the forces experienced by components, such as wings, frames, or suspensions. Robotics and Automation: Strain gauges are used in robotic joints and grippers to provide feedback on the forces applied during movement or manipulation of objects. Medical Devices: Used in prosthetics, where they help measure forces and movements to improve control and feedback in devices like artificial limbs. Sensor Classifications Accelerometer Sensor (Mechanical Sensor) Working Principle An accelerometer is a device that measures acceleration forces acting on it. Its depends on their sensing technology Capacitive Accelerometers: Use micro-electromechanical systems (MEMS) technology. Consist of a mass suspended by springs and a fixed plate. When acceleration occurs, the mass moves, changing the capacitance between the mass and the fixed plate, which is converted into an electrical signal. Piezoelectric Accelerometers: Utilize piezoelectric materials that generate an electrical charge when subjected to mechanical stress. When the sensor experiences acceleration, the piezoelectric material deforms, producing a voltage proportional to the acceleration. Sensor Classifications Accelerometer Sensor (Mechanical Sensor) Applications Smartphones and Tablets: Used for screen orientation detection (landscape or portrait mode), motion sensing for gaming, and step tracking in health apps. Automotive: Found in airbag systems to detect rapid deceleration or crash impact, and in electronic stability control systems to enhance vehicle safety and performance. Wearable Devices: Utilized in fitness trackers and smartwatches for activity monitoring, such as counting steps, tracking workouts, and measuring sleep patterns. Industrial Monitoring: Used to monitor vibrations and movement in machinery to predict maintenance needs and prevent failures. Robotics: Helps robots understand their orientation and movement in space, improving navigation and control. Sensor Classifications Tilt Sensor (Mechanical Sensor) Working Principle A tilt sensor measures the angle of inclination or tilt relative to the vertical or horizontal axis. There are several types of tilt sensors, each utilizing different principles: Mechanical Tilt Sensors: Often use a ball or pendulum that rolls or swings in response to tilt. When tilted, the ball moves to one side, completing a circuit or changing resistance, which indicates the angle of tilt. Capacitive Tilt Sensors/inclinometer sensor: Utilize capacitive sensing to measure changes in capacitance caused by the displacement of a conductive mass. The sensor has electrodes that detect changes in capacitance as the tilt angle changes. Sensor Classifications Tilt Sensor (Mechanical Sensor) Applications Automotive Systems: Used in vehicle stability control systems, providing data for active safety features and stability management. Construction and Civil Engineering: Monitors the tilt of structures, such as bridges and buildings, to ensure safety and structural integrity. Home Automation: Employed in smart home devices to detect the orientation of equipment, such as lights or alarms. Sensor Classifications Thermistor (Temperature Sensor) Working Principle A thermistor is a type of resistor whose resistance varies significantly with temperature. There are two main types of thermistors: Negative Temperature Coefficient (NTC) Thermistors: The resistance decreases as the temperature increases. Commonly used for temperature measurement and control. Positive Temperature Coefficient (PTC) Thermistors: The resistance increases as the temperature increases. Often used for overcurrent protection and self-regulating heating elements. Sensor Classifications Thermistor (Temperature Sensor) Applications Temperature Measurement: Used in medical devices (e.g., digital thermometers) to measure body temperature accurately. HVAC Systems: Employed in heating, ventilation, and air conditioning systems for temperature control and regulation. Battery Management Systems: Monitors the temperature of batteries to prevent overheating and ensure safety. Automotive Applications: Used in engine temperature monitoring and climate control systems in vehicles. Consumer Electronics: Found in household appliances like ovens, refrigerators, and air conditioners for precise temperature regulation. Sensor Classifications Infrared Thermal Sensor (Temperature Sensor) Working Principle An infrared (IR) thermal sensor measures the temperature of an object by detecting the infrared radiation emitted by it. All objects emit IR radiation based on their temperature, and the amount of radiation increases with temperature. The sensor converts this radiation into an electrical signal that can be quantified as temperature. Applications Medical Devices: Used in non-contact infrared thermometers for measuring body temperature (e.g., forehead thermometers), especially important during health screenings and pandemics. Industrial Monitoring: Employed in manufacturing processes to monitor temperatures of machinery and materials, ensuring optimal operating conditions and preventing overheating. Fire Detection Systems: Used in fire alarms and surveillance systems to detect temperature changes that indicate the presence of fire. Sensor Classifications Sound Sensor (Acoustic Sensor) Working Principle A sound sensor, also known as an acoustic sensor or microphone, detects sound waves and converts them into electrical signals. Sound waves are pressure variations in the air, and when these waves hit the sensor, they cause a mechanical or electrical response. Most sound sensors work based on microphones that can capture sound and convert it into an analog or digital signal for further processing. Most common sound sensors: Condenser (Capacitor) Microphone Consists of a diaphragm that acts as one plate of a capacitor, with the other plate being fixed. When sound waves hit the diaphragm, it vibrates, causing changes in the capacitance, which is then converted into an electrical signal. Sensor Classifications Sound Sensor (Acoustic Sensor) Applications Voice-Activated Devices: Used in smart assistants (e.g., Amazon Alexa, Google Assistant) and voice-controlled systems that detect the user’s voice to perform tasks or issue commands. Sound Level Monitoring: Deployed in industrial settings to monitor noise levels and ensure they do not exceed safe limits (e.g., in factories or construction sites). Security Systems: Employed in systems to detect glass breaking, loud noises, or unusual sounds to trigger alarms. Hearing Aids: Built into hearing aids to amplify sound for those with hearing impairments. Robotics and Automation: Used in robots for sound localization and interaction with the environment, such as responding to claps or spoken commands. Sensor Classifications Ultrasonic Sensor (Acoustic Sensor) Working Principle An ultrasonic sensor uses high-frequency sound waves (ultrasound, typically in the range of 20 kHz to 40 kHz, which is beyond human hearing) to measure the distance to an object. It works on the principle of echo or time of flight—sending out sound pulses and measuring the time it takes for the echoes to return after bouncing off an object. The sensor typically consists of two components: Transmitter (Emitter) to emits an ultrasonic sound wave and receiver to detects the reflected sound wave (echo). Sensor Classifications Ultrasonic Sensor (Acoustic Sensor) Applications Obstacle Detection in Robotics: Used in robots for navigation and collision avoidance by detecting objects in the environment. Parking Sensors in Cars: Found in automotive parking assistance systems to help drivers detect obstacles while parking. Level Measurement: Used in tanks and silos to measure the level of liquids or solids by bouncing sound waves off the surface. Object Detection: Employed in conveyor belt systems, automation processes, and industrial equipment to detect the presence of objects. Distance Measurement Devices: Found in hand-held ultrasonic distance measurement tools for construction and DIY applications. Sensor Classifications Infrared Proximity Sensor (Optical Sensor) Working Principle An Infrared (IR) Proximity Sensor detects the presence of nearby objects using infrared light. The sensor emits infrared light through an IR LED, and if an object is within its range, the light is reflected back and detected by the IR receiver (a photodiode or phototransistor). The sensor then interprets the reflected light signal to determine the proximity or presence of the object.. Applications Smartphones: Used in proximity detection, for example, to turn off the screen during calls when the phone is held near the ear to prevent accidental touches. Obstacle Detection in Robotics: Used in robots to detect objects in their path, helping in navigation and collision avoidance. Automotive Applications: Integrated into parking sensors and advanced driver- assistance systems (ADAS) to detect obstacles and improve safety. Touchless Controls: Used in devices like soap dispensers, hand dryers, and water faucets, enabling hands-free operation by detecting hand proximity Sensor Classifications Photogate Sensor (Optical Sensor) Working Principle A photogate sensor is an optical sensor that uses a light beam (typically infrared) and a photodetector to detect when an object passes through or interrupts the beam. The sensor consists of an emitter, which produces the light beam, and a detector that senses the light. When an object passes between the emitter and detector, it blocks the light, triggering a detection event. Sensor Classifications Photogate Sensor (Optical Sensor) Applications Physics and Timing Experiments: Widely used in laboratory settings, especially in educational environments, to measure the time an object takes to pass through the photogate, allowing for calculations of velocity, acceleration, and other motion-related parameters. Conveyor Belt Systems: Used to detect items passing on a conveyor belt for counting, quality control, or sorting purposes. Speed Measurement: In race timing systems, photogates can be used to measure the speed of athletes or vehicles by recording the time it takes to pass between two photogates. Industrial Automation: Used to detect the presence of objects in manufacturing lines, ensuring accurate process control and positioning. Sensor Classifications Light Dependent Resistor (LDR) Sensor (Light Sensor) Working Principle A photoresistor, also known as a light-dependent resistor (LDR), is a passive electronic component whose resistance decreases as the intensity of light falling on it increases. It is made from semiconductor materials like cadmium sulfide (CdS) that change their conductivity based on light exposure. When light photons hit the surface of the photoresistor, they provide enough energy to free electrons, reducing the resistance of the material and allowing more current to pass through. In darkness or low light: The resistance of the photoresistor is high, allowing very little current to pass. In bright light: The resistance decreases significantly, allowing more current to flow through the circuit. Sensor Classifications Light Dependent Resistor (LDR) Sensor (Light Sensor) Applications Automatic Lighting Systems: Used in streetlights and garden lights, where the photoresistor detects ambient light levels and automatically switches the lights on at dusk and off at dawn. Light Meters: Found in photographic equipment to measure the intensity of light, ensuring correct exposure settings. Brightness Control: In devices like smartphones and televisions, photoresistors are used to adjust screen brightness automatically based on ambient lighting conditions. Security Systems: Employed in alarms and motion detectors where light levels are used as a trigger to detect intrusion. Solar Garden Lights: Photoresistors are used to activate lights at night, utilizing solar energy stored during the day. Sensor Classifications Humidity Sensor (Environmental Sensor) A humidity sensor, also known as a hygrometer, measures the moisture content in the air (relative humidity or absolute humidity). Two common types of humidity sensors based on their sensing mechanism Capacitive Humidity Sensors: Working Principle: These sensors measure humidity by detecting changes in capacitance. The sensor consists of two electrodes with a hygroscopic (moisture- absorbing) dielectric material between them. As humidity increases, the dielectric absorbs more moisture, altering the capacitance, which is measured and converted into a humidity reading. Resistive Humidity Sensors: Working Principle: In resistive sensors, the sensor's resistance changes as the surrounding humidity levels change. The sensor uses a conductive material whose resistance decreases with increasing moisture content. The change in resistance is used to calculate the humidity. Sensor Classifications Humidity Sensor (Environmental Sensor) Applications Weather Monitoring: Used in meteorological stations to measure humidity as part of weather forecasting. Agriculture: Essential in monitoring soil and air humidity for optimizing irrigation and controlling greenhouse environments. Home Appliances: Integrated into dehumidifiers, humidifiers, and smart thermostats to regulate indoor air quality. Industrial Processes: Used in manufacturing industries where humidity control is critical, such as pharmaceutical production, electronics manufacturing, and food storage. Sensor Classifications Soil Moisture Sensor (Environmental Sensor) A soil moisture sensor measures the water content in the soil by detecting the soil’s conductivity, resistivity, or dielectric constant. The two most common types of soil moisture sensors are: Capacitive Soil Moisture Sensors: Working Principle: This type of sensor measures the dielectric constant of the soil, which changes based on moisture content. The sensor consists of two metal plates that form a capacitor. When soil moisture changes, the capacitance between the plates changes, which is measured and translated into a moisture level. Resistive Soil Moisture Sensor: Working Principle: Resistive sensors measure soil moisture by passing a current through the soil and measuring its resistance. Water in the soil decreases resistance, while dry soil has higher resistance. The change in resistance is used to estimate moisture levels. Sensor Classifications Soil Moisture Sensor (Environmental Sensor) Applications Irrigation Systems: Used in agriculture and gardening to optimize watering schedules based on soil moisture levels, helping to conserve water and improve crop yield. Smart Agriculture: Integrated into precision farming technologies, enabling farmers to monitor and control irrigation based on real- time data. Greenhouse Automation: Used to automatically adjust watering systems in greenhouses to maintain optimal soil moisture for plant growth. Home Gardening: Found in smart plant watering systems, providing data to ensure plants receive adequate water without overwatering. Sensor Classifications Touch Sensor (Input Sensor) Working Principle A capacitive touch sensor is an input device that detects touch and proximity through the electrical properties of the human body. It consist of an array of capacitive elements that detect changes in capacitance when a conductive object (such as a human finger) comes into proximity. Applications Smartphones and Tablets: Capacitive touch sensors are the primary input method for most mobile devices, allowing for intuitive navigation and interaction. Touch Screen Monitors: Used in kiosks, tablets, and interactive displays, enabling user-friendly interfaces. Home Appliances: Integrated into touch-sensitive controls for ovens, washing machines, and other smart home devices. Wearable Devices: Found in smartwatches and fitness trackers, allowing users to interact with the device through touch gestures. Choosing a Sensor 1 Application Needs 2 Sensor Type 3 Sensor Specifications Consider the specific requirements Different sensor types are suited for Pay attention to the sensor's sensitivity, of your application, such as the different physical quantities. For resolution, accuracy, response time, and range of values to be measured, the example, a pressure sensor measures operating temperature range. desired accuracy, and the force per unit area, while a temperature operating environment. sensor measures heat. 4 Cost and Availability Balance performance and cost considerations. Ensure the chosen sensor is readily available and affordable for your project. Sensor/Transducer Specifications Specification Description Example Operating Range The range of input quantities that the -A lab thermometer can have range of -50-200 oC sensor can accurately measure. -Ultrasonic Sensor, widely used in parking system measures It indicate the minimum and maximum distances within specific range (0 -5 meter) values , Sensitivity The ratio of the output signal change to For example, a pressure of 2 bar produces a deflection of 10 degrees the input quantity change. in a pressure transducer, the sensitivity of the instrument is 5 degrees/bar Example Sensor/Transducer Specifications Specification Description Example Resolution The smallest change in the input quantity --A Load cell measures weight and force. There are various types of that can be detected by the sensor. load cells including Smallest load cell is designed for high resolution and can detect smaller changes in weight or force Largest load cell is designed to handle larges forces or weight, it has lower resolution Accuracy The degree to which the sensor's output -a pressure gauge of range 0–10 bar has a quoted inaccuracy of ±1.0% matches the true value of the input f.s. (±1% of full-scale reading), then the maximum error to be quantity. expected in any reading is 0.1 bar. This means that when the instrument is reading 1.0 bar, the possible error is 10% of this value. Response Time The time it takes for the sensor to reach a Piezoelectric Pressure Sensor: Rapidly detects pressure changes, certain percentage of its final output value often used in dynamic environments like automotive systems. after a change in the input quantity. Technical Datasheets What is Datasheet? Key Sections of a Technical Datasheet: 1. Sensor Type & Model: Defines the category A technical datasheet provides detailed information about a (e.g.,thermocouple, strain gauge, capacitive). sensor’s performance, specifications, and capabilities. 2. Measuring Range: Specifies the range of input values the Essential for selecting the right sensor for specific sensor can accurately detect (e.g., temperature, pressure). 3. Sensitivity: Indicates how much the output changes with a applications small change in input (e.g., mV/°C for thermocouples). 4. Accuracy: Describes the difference between the measured Why are datasheets important? value and the true value. 5. Resolution: Smallest detectable change in the input signal. 6. Response Time: Time it takes for the sensor to respond to Informed Selection: Helps in choosing the right sensor for a changes in the input. particular application. 7. Operating Temperature: The range within which the sensor operates effectively. Comparison: Allows for side-by-side comparison of multiple 8. Power Requirements: Voltage or current needed for sensors. operation. Performance Assessment: Ensures that the sensor fits the 9. Environmental Conditions: Specifications for humidity, pressure, vibration, etc. environment and use case (e.g., operating range, accuracy).s Activity 4: Analyze the Sensor Spec Analyze the TMP36 temperature sensor using datasheet Download the Datasheet Go to google or any web browser and search TMP36 datasheet Analyse each key section 1. Sensor Type & Model 2. Measuring Range 3. Sensitivity 4. Accuracy 5. Resolution 6. Response Time 7. Operating Temperature 8. Power Requirements 9. Environmental Conditions Content Outline Signal Conditioning Introduction Sensor Conversion Circuits Signal Conditioning Functions Operational Amplifiers Signal Conditioning Protections Analog-to-Digital Converter (ADC) Conclusions Introduction Signal conditioning refers to the manipulation of a signal in a way that prepares it for the next stage of processing. This can include amplification, filtering, and converting the signal into a usable format. Importance of Signal Conditioning In sensor systems, the signals generated can be weak, noisy, or in a non- digital format 1 Signal Enhancement 2 Compatibility Signal conditioning improves Signal conditioning ensures the quality and reliability of compatibility between signals by amplifying, sensors and the filtering, and converting measurement system, them. enabling seamless data transmission. Signal Conditioning Functions 1. Amplification Function: Increases the amplitude of weak signals to match the input range of the data acquisition system or ADC. Example: Amplifying small voltage signals from a thermocouple or strain gauge to be measurable by the ADC. 2. Attenuation Function: Reduces the amplitude of signals that are too large for the input range of the ADC or processing system. Example: Scaling down high-voltage signals from industrial sensors to a safe level for an ADC (e.g., converting a 10V signal down to 5V). Signal Conditioning Functions 3. Filtering Function: Removes unwanted frequency components (such as noise or interference) from the signal, ensuring accurate signal representation. Example: An anti-aliasing filter is used before digitizing a signal to prevent higher frequencies from distorting the measurement. 4. Excitation Function: Supplies the required voltage or current to passive sensors such as RTDs (Resistance Temperature Detectors) or strain gauges. Example: Providing constant current excitation to a strain gauge to measure its resistance change as strain is applied. There are signal conditioning functions such as Isolation, Linearization, impedance matching, multiplexing and offset removal Sensor Conversion Circuits Sensors convert physical phenomena into electrical signals, but the output signal from many sensors is often not directly usable by most systems. To process these signals, conversion circuits are necessary to translate the sensor’s output into a form that can be interpreted by control systems or microcontrollers. 1 Voltage Divider A voltage divider is one of the simplest conversion circuits, typically used for resistive sensors (e.g., thermistors, LDRs). 2 Wheatstone Bridge A Wheatstone Bridge is commonly used with sensors like strain gauges and load cells to accurately measure small changes in resistance. Conversion Circuits Voltage Divider A voltage divider consists of two resistors in series. One of these resistors is usually a variable sensor (e.g., a thermistor/LDR whose Vin resistance changes with temperature). The output voltage is taken from the junction between the two resistors and is proportional to the sensor’s resistance. RLDR Formula Vout R1 Applications LDR is used for light measurement Thermistor for temperature sensing Conversion Circuits Voltage Divider Vin Example Given the value of Vin is 3 V and fixed resistor (R1) is 1k Ω, calculate the output VinR voltage (Vout) the following light conditions, where RLDR represents the LDR resistance of the LDR: Bright light: RLDR = 506 Ω Medium light: RLDR = 900 Ω Dim light: RLDR = 180 kΩ R1 Vout Conversion Circuits Wheatstone Bridge The Wheatstone Bridge is a circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit. Offering high precision and versatility across various applications Circuit Configuration Consists of Four resistors: Two known resistors (R1 and R2) One unknown resistor (Rx) One variable resistor or potentiometer (R3) Power source and voltmeter Applications Strain Gauges: Employed in structural engineering to measure deformation. Load Cells: Utilized in weighing systems for accurate weight measurement Conversion Circuits Wheatstone Bridge Basic Principle The Wheatstone Bridge operates on the principle of null detection. When the bridge is balanced, the potential difference between the two midpoints is zero, allowing for the calculation of unknown resistances without the influence of current flow through them. At Balance condition, Rearrange this equation to solve Rx (Rx = R4) This indicates that in a balanced Wheatstone bridge, the ratios of the resistances are equal, resulting in zero output voltage (Vout =0) Conversion Circuits Unbalanced Wheatstone Bridge Basic Principle When the bridge becomes unbalanced, the resistances on the two sides are no longer proportional, and a measurable output voltage (Vout) appears. This output can be used to calculate the deviation of the unknown resistor from its balanced value. The output voltage ( Vout) for an unbalanced Wheatstone bridge can be calculated using the formula: Vout = VC-VD Conversion Circuits Example You are given a Wheatstone bridge circuit with the following resistances: R1 = 80 Ω, R2 = 120 Ω , R3 = 480 Ω and R4 is the unknown sensor value. Calculate 1. The value of R4 that will balance the Wheatstone bridge 2. The output voltage if R4 = 170 Ω. 9V Activity 5: Tinkercad Simulation Objective: To simulate the behaviour of LDR and observe the output voltage changes 1. LDR values: - Insert the LDR (Light Dependent Resistor) and Multimeter components. - Connect the LDR to a multimeter to measure resistance. - Observe the resistance changes when varying the light intensity. - Record the resistance values for three conditions: highest, intermediate, and lowest light intensity. 2. Output voltage: - Using Tinkercad, build the circuit as shown in the previous example (refer to Figure). Light Intensity LDR Values Output Voltage - Add the following components: A 3V battery and a fixed resistor of 1kΩ Level (Ω) (V) - Connect the LDR in the voltage divider configuration with the fixed resistor. Highest - Measure the voltage output across the fixed resistor using the multimeter. Intermediate - Record the output voltage under different light intensities: highest, Lowest intermediate, and lowest. - Compare how the output voltage varies with the changes in light intensity. Activity 5: Tinkercad Simulation Assignment: Modify the circuit by replacing the fixed resistor with other values: 500 Ω and 10 kΩ For each fixed resistor value, measure the output voltage across the fixed resistor for the three light intensity levels: high, medium, and low. Compare the output voltage for each fixed resister value. Which fixed resistor provide the maximum sensitivity to temperature changes.? Light Intensity Output Voltage (V) Level Fixed Resistor Fixed Resistor Fixed resistor 1k Ω 500 Ω 10 kΩ Highest Intermediate Lowest Activity 6: Tinkercad Simulation Objective: To simulate the Wheatstone Bridge and analyze the effect of changing sensor resistance on the output voltage Procedures 1. Create a new circuit 2. Add the following components: 4 Resistors (set R1 = 80 Ω, R2 = 120 Ω , R3 = 480 Ω and R4 = 170 Ω Battery (9V) Multimeter (set to volt) 3. Build the Wheatstone bridge, connect the circuit as per the Wheatstone bridge diagram. 4. Run the simulation, measure and observe the output voltage Activity 6: Tinkercad Simulation Assignment: Change R4 to 720 Ω. Observe the output voltage Change the input power supply (e.x 5V) and see how that affect the balance and output Try varying other resistor values and observe the output voltage changes. Additional assignment: Set all the resistors to original values, and replace resistor R4 with LDR. Record the output voltage under different light intensities: highest, intermediate, and lowest. Light Intensity LDR Values Output Voltage Level (Ω) (V) Highest Intermediate Lowest Conversion Circuits Exercise- Voltage Divider Design a precise temperature measurement using a thermistor and a fixed resistor in a voltage divider configuration. The system is powered by 5V source. Given the data measurement of thermistor: Temperature (oC) Resistance changes (kΩ) 25 10.0 35 7.5 45 5.0 1. Calculate the output voltage across the fixed resistor for the following values: a) 500 Ω b) 2.2 kΩ c) 5 kΩ 2. If you have the option to choose between fixed resistor values of 500 Ω, 2.2 kΩ and 5 kΩ for temperatue variations for temperature variations between 25 oC and 45 oC. Which one would you recommend? Why? Conversion Circuits Exercise- Wheatstone bridge You are tasked with designing a Wheatstone bridge circuit to measure the resistance of a sensor. The input voltage to the bridge is 10 V, and the known R1 R3 resistor values are as follows: Resistors Resistance values (Ω) Vin R1 150 R2 300 R2 Rx R3 450 Rx Unknown sensor resistance 1. Calculate the value of Rx that will balance the Wheatstone bridge 2. If the sensor resistance Rx changes to 600 Ω. Calculate the output voltage across the bridge. Summary on Conversion Circuits The Wheatstone bridge and voltage divider are both fundamental circuit configurations used for measuring resistances, but they have different applications, configurations, and advantages. Feature Wheatstone bridge Voltage Divider Configuration Four resistors arranged in a diamond shape with Two resistors in series with an output voltage taken a voltage output between two points. from the junction of the two Sensitivity More sensitive to small changes in resistance, Less sensitive to small changes, typically used for making it suitable for precise measurements general voltage reduction Output voltage Voltage output varies based on the relative Output voltage is a simple fraction of the input resistance values; it can be zero (balanced voltage, determined by the resistor values condition) when resistances are equal Applications Ideal for measuring unknown resistances (like Commonly used for adjusting signal levels or strain gauges) and precise sensors supplying reference voltages Imbalance detection an detect slight imbalances due to changes in Does not inherently detect imbalances; it provides a resistance, giving a measurable output. fixed output based on the resistor values. Operational Amplifiers (Op-Amps) An Operational Amplifier (commonly abbreviated as Op-Amp) is a highly versatile electronic device that can perform a wide range of analog signal processing tasks. Op-Amps are designed to amplify voltage signals and are a fundamental building block in many analog circuits. Key Characteristics of Op-Amps 2 Differential Inputs 3 High Input Impedance 1 High-Gain The input impedance of an Op-Amp is Op-Amps have a very high open-loop Op-amps have two inputs: extremely high, meaning it draws very little gain, typically in the range of 100,000 Inverting input (-): The input signal current from the input signal source. This to 1 million, making them highly applied here will result in an output ensures that the signal is not distorted when effective for amplifying weak signals. that is inverted (opposite in phase) connected to the Op-Amp. compared to the input. Non-inverting input (+): The input 4 Low Output Impedance signal applied here will result in an The output impedance of an Op-Amp output that maintains the same is very low, allowing it to drive a wide phase as the input. variety of loads without significant voltage loss. Operational Amplifiers (Op-Amps) Basic Op-Amp Configurations 1 Inverting Amplifier 2 Non-Inverting Amplifier 3 Voltage Follower (Buffer) Input is applied to the inverting Input is applied to the non-inverting Provides a unity gain (output equals terminal, output is 180 ᵒ out of terminal, output is in phase with input input) phased Function: Amplifies the input signal Function: Provide high input impedance Function: Inverts and amplifies without inversion and low output impedance the input signal Rf Rf Rin Rin Operational Amplifiers (Op-Amps) More Op-Amp Configurations 4 Voltage Comparator 5 Differential Amplifier 6 Summing Amplifier Compares two input voltages and Amplifies the difference between two Adds multiple input voltages together, outputs a high or low signal based inputs signals while rejecting noise usually based on the inverting amplifier on comparison Function: Used in precision Function: Combine multiple signals into Function: Converts analog to measurement one output, used in audio mixing or digital levels: used in decision- signal processing making circuits Rf R1 Rf R1 V1 V2 R2 V3 R1 Rf R3 Operational Amplifiers (Op-Amps) More Op-Amp Configurations 7 Integrator Amplifier 8 Differentiator Amplifier Uses a capacitor in the feedback loop. The output Uses a capacitor at the input. The output voltage is voltage is proportional to the integral of the input proportional to the rate of change (derivative) of the input voltage over time. voltage. Function: Converts a time-varying input signal into its Function: Detects changes in the input signal and outputs a integral. It smooths signals and is used in applications signal proportional to the rate of change. Used in high- like signal processing or analog computation speed signal detection and edge detection. Operational Amplifiers (Op-Amps) Inverting Amplifier In an inverting amplifier, the input signal is applied to the inverting terminal (-) of the Op-Amp, and the non-inverting terminal (+) is connected to ground. The feedback resistor connects the output to the inverting input, and this configuration produces an output signal that is inverted (180° phase shift) and amplified based on the resistor values. Equation Key Characteristics Applications Phase: Output is inverted (180o phase shift) Signal inversion and amplification. Gain: Controlled by resistor ratio (Rf/Rin) Audio processing circuits. Analog computation in summing or subtracting signals. Operational Amplifiers (Op-Amps) Non-Inverting Amplifier In a non-inverting amplifier, the input signal is applied to the non-inverting terminal (+), and the feedback loop is connected from the output to the inverting terminal (-). The result is an amplified output signal that is in phase with the input. Equation Key Characteristics Applications Phase: Output is in phase with the input (0° Signal amplification without phase inversion. phase shift). Buffering weak sensor signals. Gain: Greater than 1 and controlled by the resistor ratio (1 + Rf/Rin) Operational Amplifiers (Op-Amps) Voltage Follower (Buffer Amplifier) A voltage follower (also called a buffer amplifier) is a special case of the non-inverting amplifier. In this configuration, the output is directly connected to the inverting terminal (-) (Rf = 0 and Rin → ∞), and the non-inverting terminal (+) Key Characteristics Phase: Output is in phase with the input (0° phase shift). receives the input. Gain: 1 (no amplification, only buffering). This creates a unity gain amplifier where the output voltage is equal to Eliminate loading effects (High input impedance and the input low output impedance) Equation Applications Buffering between circuits to prevent loading effects. Signal isolation. Operational Amplifiers (Op-Amps) Voltage Comparator A voltage comparator compares two input voltages and produces an output indicating which input is larger. Operation If the voltage at the non-inverting terminal (+) is greater than the voltage at the inverting terminal (-), the output will saturate to the positive supply voltage (+V). If the voltage at the inverting terminal (-) is greater than the voltage at Key Characteristics the non-inverting terminal (+), the output will saturate to the negative Phase: No phase consideration since it’s a digital- supply voltage (-V or ground). like output (high or low). Gain: Not applicable, as it doesn’t amplify but compares two voltages. Applications Used in decision-making circuits like threshold detectors or zero-crossing detectors. Operational Amplifiers (Op-Amps) Differential Amplifier A differential amplifier amplifies the difference between two input signals, making it highly useful in measurement systems where noise rejection is needed. The output voltage is proportional to the difference between the voltages at the two inputs. Equation Key Characteristics Phase: Amplifies the difference between two Applications signals, no specific phase shift. Gain: Defined by the feedback and input Used in sensor signal conditioning, especially for differential resistances (Rf/Rin) signals like strain gauges or thermocouples. Operational Amplifiers (Op-Amps) Summing Amplifier A summing amplifier is an Op-Amp configuration that produces an output proportional to the sum of multiple input voltages. It is useful in analog computing and audio mixing systems. Multiple input voltages are applied to the inverting terminal of the Op-Amp through individual resistors. The output is the weighted sum of the input voltages. Equation Key Characteristics Phase: Output is inverted (180° phase shift). Gain: Determined by the ratio of feedback Applications resistance to input resistances. Common in audio mixing, and signal processing. Operational Amplifiers (Op-Amps) Example 1 – Inverting amplifier You are working on a project to read data from a thermistor-based temperature sensor. The thermistor produces a voltage signal ranging from 0.5V to 2.5V depending on the temperature. However, your analog-to-digital converter (ADC) can only read voltages between -5V and 0V. 1. You need to design a circuit that scales and inverts the thermistor signal to match the ADC’s input range. A feedback resistor Rf of 100 kΩ is used. 2. If the thermistor outputs =1.5V, calculate the corresponding output voltage. Solution 1. Design an inverting op-amp circuit (amplify and invert the input), Redraw the inverting amplifier Thermistor output voltage, Vin ranges from 0.5V to 2.5 V, 100 kΩ Desire output voltage, Vout ranges from -5 V to 0V Find Av = Vout/Vin= 5/2.5 = -2.5 (inverting gain) 40 kΩ Solve for Rin How about question 2? Operational Amplifiers (Op-Amps) Example 2 – Non-inverting amplifier You are working with a LDR sensor with the voltage divider circuit that outputs a voltage signal ranging from 0.1V to 2.0V, but the device you’re using to read the signal requires a higher voltage range of 0V to 5V for better accuracy. Design a non- inverting amplifier circuit to amplify the sensor output to the desired range. The input resistor Rin is 10kΩ. Solution 1. Design an non-inverting op-amp circuit (amplify without phase inversion), Pressure output voltage, Vin ranges from 0.2V to 0.8 V, Desired output voltage, Vout ranges from 0 V to 4 V Find Av Solve for Rf Redraw the non-inverting amplifier Activity 7: Tinkercad Simulation Objective: To simulate non-inverting amplifier 1. Operational amplifier circuit: Open the existing project (Activity 5) that includes the LDR and the voltage divider configuration Add an operational amplifier (OpAmp IC 741) to the workspace and two resistors 10 kΩ (Rin) and 15 kΩ (Rf). Use 9 V power supply for the amplifier Connect the output of the voltage divider to the non-inverting input of amplifier Measure the Vo and V1 using a multimeter Light Intensity V1 Vo Level Highest V1 Intermediate V1 Lowest Operational Amplifiers (Op-Amps) Example 3 – Differential amplifier Design a differential amplifier circuit to measure the voltage difference across a sensor that outputs a small differential voltage signal. The sensor produces output voltages V1 = 1.5 V and V2 = 1.2 V. The differential amplifier needs to provide an output voltage that amplifies the difference between these two signals by a factor of 10. 1. Calculate the input voltage difference Vin. 2. Given Rf = 100 kΩ. Determine the resistor R1 values needed for the desired gain. 3. Calculate the output voltage, Vout. 4. Draw the complete differential amplifier circuit. Signal Conditioning Protection refers to techniques and components used to safeguard signals from unwanted effects such as noise, distortion, and voltage spikes, ensuring accurate data transmission and processing. Common threats 1 Noise 2 Voltage Spikes Sources: Electromagnetic interference Causes: Sudden changes in current, (EMI), radio frequency interference inductive kickback from motors, (RFI), and thermal noise. lightning strikes, or switching Effects: Decreases the signal-to-noise operations. ratio (SNR), leading to inaccurate Effects: Can damage sensitive readings and errors. electronic components and lead to signal distortion. 3 Overvoltage Causes: Power surges or incorrect power supply levels. Effects: Can result in permanent damage to sensors and signal conditioning circuits. Signal Conditioning Protection Protection Techniques 1 Voltage Clamping Prevent overvoltage conditions by diverting excess voltage away from sensitive components. Component: Zener Diodes- Used to clamp voltage to a specified level, protecting against spikes. Application: Typically placed in parallel with the load or input to absorb excess voltage. 2 Fuses and Circuit Breaker Protect against overcurrent situations that could lead to component failure. Components: Fuses- Melt and break the circuit when the current exceeds a specified level. Circuit Breakers: Automatically switch off the circuit in case of overloads, allowing for manual reset. Application: Essential for power supply protection in electronic devices. Analog-to-Digital Converters (ADC) An Analog-to-Digital Converter (ADC) is an electronic device that converts continuous analog signals, such as voltage or current, into digital data that can be processed by computers, microcontrollers, or other digital systems. Importance of ADC ADCs are crucial in interfacing the real world (which is analog) with digital systems, enabling the conversion of physical quantities like temperature, pressure, sound, and light into a format that can be processed and analyzed. 1 Digital signals 2 Digitization Most sensors and ADCs enable the digitization transducers generate analog of real-world data for further signals, while modern manipulation, storage, and processing units (e.g., decision-making in digital microcontrollers, DSPs) systems. work with digital signals Analog-to-Digital Converters (ADC) Key Specifications of ADCs 1 Resolution 2 Sampling Rate The number of bits (e.g., 8-bit, 12- Defines how frequently the ADC bit) determines how accurately the samples the analog signal (measured in ADC can represent the analog samples per second, Sps). Higher input. Higher resolution = more sampling rates capture more signal precision. details but often require more Example: 8 bit ADC processing power and memory. 3 Input range ADCs are central to data acquisition systems that collect The range of input voltages the ADC can accept. Signals must be data from sensors (e.g., temperature, pressure, conditioned (e.g., amplified or attenuated) to fit within this range humidity). Before the analog signal reaches the ACD, it for accurate conversion. may need to be conditioned Analog-to-Digital Converters (ADC) Common ADC Types 1 SAR (Successive 2 Flash ADC 3 Delta-Sigma ADC Approximation ADC) Provides a balance of speed and Extremely fast, but power-hungry and Offers high resolution but slower speed. accuracy; commonly used in expensive. Used in high-speed Suitable for precision applications like general-purpose applications. applications like video or radar. audio and sensor data. Type of ADC in Arduino Boards Analog-to-Digital Converters (ADC) SAR (Successive Approximation ADC) The Successive Approximation Register (SAR) ADC is a type of analog-to-digital converter that converts an analog signal into a digital output using a binary search algorithm. It is widely used in applications requiring moderate speed, high resolution, and low power consumption. Function Blocks of SAR ADC Sample and Hold Circuit (S/H): Captures and maintains the input voltage (Vin) during the conversion process. Analog Voltage Comparator: Compares the held input voltage (Vin) with the output voltage from the internal Digital-to-Analog Converter (DAC) and sends the comparison result to the Successive Approximation Register (SAR). Successive Approximation Register (SAR): Generates an approximate digital code corresponding to the input voltage (Vin) based on the comparison results received from the voltage comparator, which it uses to update the internal DAC. Internal Reference DAC: Converts the digital code output from the SAR back into an analog voltage, which is then provided to the comparator for further comparisons. Analog-to-Digital Converters (ADC) Converting Digital Value from Analog Voltage Resolution The resolution of an ADC is determined by the number of bits (𝑁) it uses to represent the analog input voltage. The total number of discrete levels (quantization levels) that the ADC can produce is given by: Example: A 4-bit ADC has 24 = 16 levels (0-15), An 10 bit ADC has 210 = 1024 (0 to 255) Reference Voltage This is the maximum voltage that the ADC can convert. The digital output will range To calculate the digital value from an analog voltage: from 0 to Vref Use the conversion formula based on the reference voltage and the number of bits. Conversion Formula Round the resulting value to the nearest whole The digital output value can be calculated using the formula: number. Convert that value to its binary representation. Analog-to-Digital Converters (ADC) Step-by Step Conversion Process (4 bit SAR ADC) Using Formula Take an example of using 4-bit SAR ADC with a reference voltage, Vref = 5 V The input voltage, Vin will be converted into a 4-bit digital output. (N=4 bits) Total levels is 16 (24)- ranging from 0 to 15. Let say Vin = 1.8 V, digital output is calculated using the formula: Digital value is 5 (rounding), binary representation in a 4-bit format is 0101. Analog-to-Digital Converters (ADC) 4.0625 V Successive Approximation Process 1st Bit- MSB Start with MSB –Compare the Vin = 1.8 V with half the reference voltage 4.375V 3.4375V Vref = 5V, midpoint is 5V/2 =2.5 V If Vin >2.5 V, the MSB remains 1; If Vin 1.25 V, the MSB remains 1; If Vin 1.5625 V If Vin >1.875 V, the MSB remains 1; If Vin