Ⅰ. Function of the sensor
Ⅱ. Classification of measurement errors
Ⅲ.Characteristics of sensor
Ⅳ. Sensor deviation
Ⅴ. Function of sensor
Ⅵ. Working principle of the sensor
Ⅶ. Chemical sensors, biosensors, MOS sensors
A sensor is a device or device that can detect, measure, and perceive various physical, chemical, or biological quantities in the environment. They enable computer systems, control systems or other equipment to acquire and process these quantities by converting these quantities into electrical or other recognizable forms of signals.
A sensor is a device used to detect events or changes in the environment and send this message to other electronic devices (such as a central processing unit), usually consisting of a sensing device and a conversion device.
In the broadest definition, a sensor is a device, module, machine or subsystem whose purpose is to detect events or changes in the environment and send the information to other electronic devices, usually a computer processor. Sensors are always used with other electronic devices.
Sensors are also used in everyday objects, such as touch-sensitive elevator buttons (haptic sensors) and lights that dim or brighten by touching the base, as well as countless applications that most people never realize. With the development of micromechanical technology and the development of easy-to-use microcontroller platforms, the application of sensors has been extended to the traditional field of temperature, pressure or flow measurement, such as MARG sensors. Additionally, analog sensors such as potentiometers and force-sensing resistors are still widely used.
Applications include manufacturing and machinery, aircraft and aerospace, automotive, medical, robotics and many other aspects of our daily lives. There are also a variety of other sensors that measure the chemical and physical properties of materials. Some examples include optical sensors for refractive index measurements, vibration sensors for fluid viscosity measurements, and electrochemical sensors for monitoring fluid pH.
The effect of a sensor's input on the output is called the sensor coefficient or sensitivity. For example, for a mercury thermometer, when the temperature rises by 1 °C, the mercury column rises by 1 cm, then the sensing coefficient of this mercury thermometer is 1 cm/°C.
A sensor is a physical device or biological organ that can detect and sense external signals, physical conditions (such as light, heat, humidity) or chemical composition (such as smoke), and transmit the detected information to other devices. "Sensor" is defined in New Webster's Dictionary as: "A device that receives power from one system and sends power, usually in another form, to a second system."
The sensitivity of a sensor indicates how much the output of the sensor changes when the measured input quantity changes. For example, if the mercury in a thermometer moves 1 cm when the temperature changes by 1°C, then the sensitivity is 1 cm/°C (assuming a linear characteristic, basically a dy/ slope). Certain sensors can also affect their measurements. For example, a room temperature thermometer inserted into a liquid hot cup cools the liquid while the liquid heats the thermometer. Sensors are usually designed to have little effect on the measured object. Making the sensor smaller can often improve this, and possibly other advantages.
Ⅰ. Function of the sensor
1. Feedback and adjustment: Sensors can provide feedback signals that enable the system to adjust its operation to achieve predetermined goals. For example, sensors in a car can monitor the operating state of the engine and adjust fuel supply and engine parameters based on sensor data.
2. Data acquisition and monitoring: Sensors can perceive various physical quantities, chemical quantities or biomass in the environment and convert them into electrical signals or other readable signals. This enables the system to collect, monitor and record data in real time to understand the changes and status of the environment.
3. Recognition and identification: Some sensors can be used to identify objects, human bodies, sounds, etc. Fingerprint sensors, image sensors, and sound sensors are all used to identify and recognize specific features.
4. Automatic control: The combination of sensors and control systems enables the system to automatically adjust operations or perform specific tasks based on the collected data. For example, temperature sensors can be used in thermostatic control systems to automatically adjust heating or cooling equipment based on real-time temperature changes.
5. Positioning and navigation: Position sensors, accelerometers and gyroscopes can help devices or systems determine their own position, direction and motion status, and are used in navigation, aviation, drones and other fields.
6. Security and Surveillance: Sensors are used to monitor changes and dangerous situations in the environment to provide early warning and protection. Fire alarms, security cameras, etc. are all security and surveillance devices based on sensor technology.
7. Environmental monitoring: Sensors can be used to monitor various parameters in the environment, such as temperature, humidity, gas concentration, etc. This is of great significance for environmental protection, weather forecasting, air quality monitoring, etc.
8. Scientific research: Sensors are widely used in scientific research and can help scientists collect experimental data and explore natural phenomena and phenomena.
9. Medical diagnosis and monitoring: In the medical field, sensors can be used to monitor physiological parameters of patients, such as heart rate, blood pressure, blood sugar, etc., for diagnosis and monitoring.
Ⅱ. Classification of measurement errors
Sensors should obey the following rules:
1. Does not affect the measured properties
2. Sensitive to the characteristics of the measurement
3. Insensitive to any other properties that may be encountered in the application
Most sensors have a linear transfer function. Sensitivity is then defined as the ratio between the output signal and the measured characteristic. For example, if a sensor measures temperature and has a voltage output, the sensitivity is constant in [V/K] units. Sensitivity is the slope of the transfer function. Converting a sensor's electrical output (such as V) to a unit of measure (such as K) requires dividing the electrical output by the slope (or multiplying by its inverse). Also, often increase or decrease the offset. For example, if a 0 V output corresponds to a -40 C input, then −40 must be added to the output.
For an analog sensor signal to be processed, or used in a digital device, it needs to be converted to a digital signal using an analog-to-digital converter.
Ⅲ.Characteristics of sensor
1. Immunity to Interference: The anti-interference of the sensor refers to the ability of the sensor to maintain stable performance in the presence of external interference sources. This is crucial for sensors that work stably in complex environments.
2.Sensitivity: The sensitivity of a sensor refers to its ability to detect changes in the target physical quantity. Highly sensitive sensors are capable of producing large responses to small changes.
3.Cost: The cost of the sensor may be a factor affecting the choice. High-performance sensors usually come with higher costs, while low-cost sensors may have some limitations in some aspects.Temperature Sensors
4.Resolution: Resolution is the minimum physical quantity change that the sensor can detect. Higher resolution means the sensor can accurately measure small changes.
5.Power Consumption: Different types of sensors consume different amounts of power. Low-energy sensors are suitable for battery-powered applications that require long periods of operation.
6.Linearity: The response of a linear sensor is linear in the entire measurement range, that is, the change of the physical quantity is proportional to the change of the sensor output. Nonlinear sensors may have different response characteristics over different ranges.
7.Accuracy: Accuracy is the error between the sensor output value and the actual physical value. High-accuracy sensors provide outputs close to actual values.
8. Response Time: Response time is the time interval from when a sensor detects a change in physical quantity to when it generates an output signal. Some applications require fast-response sensors, while others can tolerate longer response times.
9.Operating Range: The working range of the sensor is the physical quantity range in which it can operate normally. Physical quantities outside the operating range may cause sensor failure or inaccuracy.
10.Stability: The stability of a sensor refers to the repeatability and consistency of its output under the same conditions. A sensor with good stability can maintain accurate output for a long time.
Ⅳ. Sensor deviation
Since the sensor cannot replicate the ideal transfer function, several types of deviations occur that limit the sensor's accuracy:
1. Since the range of the output signal is always limited, the output signal will eventually reach a minimum or maximum value when the measured characteristic exceeds the limit. The full-scale range defines the maximum and minimum values for the property being measured.
2. Nonlinearity is the deviation of the sensor transfer function from a straight line transfer function. Typically, this is defined by the amount the sensor output deviates from ideal behavior over the full range (often expressed as a percentage of the full range).
3. In practice, the sensitivity may differ from the specified value. This is called sensitivity error. This is the error in the slope of the linear transfer function.
4. If the output signal differs from the correct value by a constant, the sensor has an offset error or bias. This is an error in the intercept of the linear transfer function.
5. Deviations caused by rapid changes in measured properties over time are dynamic errors. Typically, this behavior is described by a Bode plot, which shows the sensitivity error and phase shift as a function of the frequency of a periodic input signal.Color Sensors
6. If the output signal changes slowly independent of the measured characteristic, it is defined as drift. Long-term drift over months or years due to physical changes in the sensor.
7. The sensor may be sensitive to characteristics other than the characteristic being measured to some extent. For example, most sensors are affected by the temperature of their environment.
8. If the sensor has a digital output, the output is essentially an approximation of the measured characteristic. This error is also called quantization error.
9. If the signal is being digitally monitored, the sampling frequency may introduce dynamic errors, or aliasing errors may occur if the input variable or added noise varies periodically at frequencies close to multiples of the sampling rate.
10. A hysteresis error causes the output value to vary depending on the preceding input value. A sensor will have a hysteresis error if its output differs depending on whether the input was increased or decreased to reach a particular input value.
All of these deviations can be classified as systematic or random. Sometimes systematic errors can be compensated for by some kind of calibration strategy. Noise is a random error that can be reduced through signal processing such as filtering, often at the expense of the sensor's dynamic performance.
Ⅴ. Function of sensor
1. Measure the rotational movement of the device itself
The function of the sensor is to measure and record the position, speed, direction and other attributes of the object. Among them, measuring the rotational motion of the device itself is one of the important applications of the sensor. Through the built-in gyroscope, it can measure the movement of the mobile phone itself, and cooperate with the camera for anti-shake. This kind of application is very common in smart phones, and can improve the user experience and security of the mobile phone.
2. Convert the measured physical quantity into electric quantity
The function of the sensor is to convert various measured physical quantities into electrical quantities, and it is divided into various types such as inductive, capacitive, photoelectric and ultrasonic. Among them, the displacement sensor is a sensor that converts various measured physical quantities into electrical quantities, and is often used to measure small or large displacements. The role of the sensor is to convert various physical quantities into electrical energy and provide accurate and reliable electrical energy information for the power system.
3. Detect intake air temperature
The role of the intake air temperature sensor is to detect the intake air temperature, and convert the signal into an electrical signal and send it to the engine control module as the basis for calculating the air density. This can help the ECU calculate the air density, thereby correcting the signals of gasoline injection and ignition timing. The intake air temperature sensor is one of the very important sensors in modern cars, it can improve the utilization rate of fuel and ensure the stability and reliability of the engine.
4. Carry out the detection of object shape and size defects
The role of the sensor is to detect the shape and size of the object. Among them, the temperature measurement mechanism of metal thermal resistance and thermistor is to make the free electrons in the chaotic movement inside form a regular directional movement to make the conductor conduct electricity after the voltage is applied to both ends of the metal conductor. The temperature measurement mechanism of the thermistor is that at low temperature, the electron-hole concentration is very low and the resistivity is very large. As the temperature increases, the electron-hole concentration increases exponentially, and the resistivity decreases rapidly. Its resistance temperature characteristic is Rt= RotB(1/T-1/To). These sensors are widely used in industrial production, environmental monitoring and other fields.
5. Detect the throttle position of the engine
The role of the sensor is to detect the throttle position of the engine and provide an engine load signal. Among them, the throttle position sensor is one of the most important sensors, which can accurately detect the throttle position of the engine, thereby determining the load of the engine. This has a significant impact on the running state and performance of the engine. Therefore, sensors play a very important role in modern cars, which can help drivers find and solve problems in time and improve driving safety.
6. Convert various signals into electrical signals
The role of the sensor is to convert various signals from the outside world into electrical signals, which is one of the most important applications of the sensor. As a functional block, the sensor can process various signals, such as amplification, feedback, filtering, differentiation, storage, and remote operation. In order to detect and control various signals, it is necessary to obtain simple and easy-to-handle electrical signals, which can only be satisfied by electrical signals. Electrical signals can be easily amplified, fed back, filtered, differentiated, stored, and remotely operated, so sensors can be narrowly defined as "a type of component that converts external input signals into electrical signals."
7. Measure distance
The role of the sensor is multifaceted, and measuring distance is one of them. Ultrasonic sensors can measure the distance between objects, while infrared obstacle avoidance sensors and photoresistors can be used for obstacle avoidance and object detection. Photoelectric sensors can detect visible light and infrared radiation for industrial production and detection. Different types of sensors are suitable for different scenarios and needs. For example, ultrasonic sensors are suitable for detection in industrial production, and photoresistors are suitable for detection in industrial production. The role of sensors makes industrial production more intelligent and efficient.
8. Assisted navigation
Sensors play an important role in navigation, one of which is aided navigation. By measuring the altitude, it is possible to understand the movement trajectory of the vehicle in real time and help the driver avoid getting lost or going in the wrong direction. Without the need to turn on the GPS, it can also reduce driver fatigue and errors, and improve driving safety. Therefore, sensors play an indispensable role in auxiliary navigation, providing drivers with a more convenient and accurate navigation experience.
9. Measuring the pressure difference inside and outside the equipment
The function of the differential pressure sensor is to measure the pressure difference inside and outside the equipment, which can be used to monitor the pressure difference inside and outside the current equipment. It can quickly and accurately obtain the pressure difference between the inside and outside of the device, and convert it into a readable value to provide detailed pressure information for the device. This is very important for the management and maintenance of equipment, and can help users discover and solve equipment failures in time to ensure the normal operation of equipment. At the same time, the differential pressure sensor is also one of the indispensable sensors in the field of industrial automation, and is widely used in industrial production, energy, environmental protection and other fields.
10. Measure the magnetic field
The role of the sensor is to identify obstacles, open-loop current sensors, closed-loop current sensors, magnetic sensors, and Hall switch sensors. Among them, measuring magnetic fields is an application of magnetic sensors, which are commonly found in smartphones and compass applications. Magnetic sensors can be used to detect magnetic fields to help users indicate the Earth's North Pole, map navigation, and more. Also, some applications use magnetic sensors to detect metals. Sensors are widely used in industry, agriculture, lighting and other industries.
11. Identify obstacles
The role of the sensor is to identify obstacles, including open-loop current sensors, closed-loop current sensors, and Hall switch sensors. These sensors can be used to measure magnetic fields, measure magnetic fields, prevent drops, and more. Among them, the Hall switch sensor can be used in places such as motor speed measurement/position detection, and is mainly used as a switch. Anti-drop sensors can be used to prevent falls, anti-collision sensors can be used to prevent collisions and grayscale sensors can be used for quality control in the lighting industry. These sensors are widely used in industrial production, medical treatment, agriculture and other fields.
12. One feeling, two passes
One of the functions of the sensor is "one sense and two transmission", that is, the sensor can directly sense the change of the measured object and convert it into an output signal that has a definite relationship with the measured object, and then convert the output signal into a circuit parameter through the conversion element, and finally output A physical quantity such as electricity or electric energy. The sensor is composed of three parts: sensitive element, sensing element and conversion circuit. It is a device that can accurately measure the measured physical quantity. Sensors are widely used, such as temperature sensors, pressure sensors, distance sensors, etc.
Ⅵ. Working principle of the sensor
Resistive sensors use the property that the resistance value of an object changes with changes in physical quantities. For example, a temperature sensor uses the resistance value of an object to change with temperature. After measuring the change in resistance value, a bridge circuit or other circuits convert the changed resistance into a voltage or current signal.
Accelerometers measure the acceleration of an object, that is, the change in acceleration of an object in a specific direction. This can be achieved through methods such as mass-based systems (such as micromechanical systems) or capacitance changes.
Photosensitive sensors are based on the sensitivity of objects to light. When the light sensor (photoresistor or photodiode) changes in light intensity, its resistance or current value also changes, thereby generating a corresponding electrical signal.
Sound sensors sense sound based on the mechanical vibration of sound waves. Sound fluctuations cause mechanical movement of the sensor element, and changes in this movement can be converted into electrical signals.
Pressure sensors are based on the effect of the amount of pressure on an object on its specific parameters (such as resistance, capacitance, vibration frequency, etc.). Changes in these parameters can be converted into electrical signals proportional to pressure.
Gas sensors can sense the concentration of specific gases in the environment. For example, gas sensors can use chemical reactions to measure changes in gas concentration, which are then converted into electrical signals.
Ⅶ. Chemical sensors, biosensors, MOS sensors
1. Chemical sensor
A chemical sensor is a self-contained analytical device that provides information about the chemical composition of its environment (i.e., liquid or gas phase). The information is provided in the form of measurable physical signals that are related to the concentration of certain chemical substances called analytes.
The function of chemical sensors involves two major steps, recognition and transduction. In the recognition step, analyte molecules selectively interact with receptor molecules or positions contained in the structure of the recognition element of the sensor. As a result, characteristic physical parameters change and this change is reported by the integrated transducer that generates the output signal.
Chemical sensors that recognize materials based on biological properties are biosensors. However, a clear distinction between biosensors and standard chemical sensors is superfluous since synthetic biomimetic materials will to some extent replace accepted biological materials. Typical biomimetic materials for sensor development are molecularly imprinted polymers and aptamers.
In biomedicine and biotechnology, sensors that detect analytes due to biological components such as cells, proteins, nucleic acids or biomimetic polymers are called biosensors. Whereas non-biological sensors for biological analytes and even organic (carbon chemical) sensors are also called sensors or nanosensors.
Encapsulation of biological components in biosensors presents slightly different problems than ordinary sensors. This can be done with semipermeable barriers, such as dialysis membranes or hydrogels or 3D polymer matrices, that physically confine sensing macromolecules or chemically confine macromolecules by binding them to scaffolds.
The MOS sensor is a sensor based on a metal-oxide-semiconductor structure, which is mainly used to detect changes in environmental parameters such as gas concentration, chemical substances, and humidity. Their working principle involves the change of electrical properties of semiconductor materials in the presence of different gases or substances. The basic structure of MOS sensors includes semiconductor materials, metal electrodes, and oxide layers.
Metal Oxide Semiconductor (MOS) technology is derived from the MOSFET (MOS Field Effect Transistor or MOS Transistor), invented by Mohamed M. Atalla and Dawon Kahng in 1959 and demonstrated in 1960. MOSFET sensors (MOS sensors) were later developed and since then they have been widely used to measure physical, chemical, biological and environmental parameters.