Sensor丨Common classification and its application


Published:

Dec 12,2022

In today's information age, sensors have already penetrated into a wide range of fields such as industrial production, space development, ocean exploration, environmental protection, resource investigation, medical diagnosis, bioengineering, and even cultural relic protection. It is no exaggeration to say that from the vast space, to the vast ocean, to various complex engineering systems, almost every modern project is inseparable from various sensors. Today, let's take a brief look at sensors.

In today's information age, sensors have already penetrated into a wide range of fields such as industrial production, space development, ocean exploration, environmental protection, resource investigation, medical diagnosis, bioengineering, and even cultural relic protection. It is no exaggeration to say that from the vast space, to the vast ocean, to various complex engineering systems, almost every modern project is inseparable from various sensors. Today, let's take a brief look at sensors.

1. Sensor definition
A device or device that can sense a specified measured value and convert it into a usable signal according to a certain rule (mathematical function rule), usually a device consisting of a sensitive element and a conversion element, that is, a sensor. Sensors convert physical parameters (for example: temperature, blood pressure, humidity, speed, etc.) into signals that can be measured electrically. We can start by explaining the temperature example, the mercury in the glass thermometer causes the liquid to expand and contract, converting the measured temperature into a temperature that can be read by an observer on a calibrated glass tube.

Second, the principle of sensor selection

When selecting a sensor, certain characteristics must be considered, as follows:

1. Accuracy——The accuracy of the sensor only needs to meet the accuracy requirements of the entire measurement system, and it does not have to be too high. Usually, the higher the accuracy, the more expensive it is.

2. Line type range——The range in which the input is proportional to the output

3. Measurement environment——Generally there are requirements for temperature/humidity

4. Calibration——essential to most measuring equipment as readings change over time

5. Stability——After the sensor is used for a period of time, its ability to maintain the same performance is called stability.

Three, the main classification of sensors

Sensors are divided into the following standards:

1. The main input quantity (measured object), also known as the use, is divided into pressure sensitive and force sensitive sensors, position sensors, liquid level sensors, energy consumption sensors, speed sensors, acceleration sensors, radiation sensors, thermal sensors sensors etc.

2. Measuring purpose (using physical and chemical effects)

Physical sensors are made by using the characteristic that certain physical properties of the measured substance change significantly. Chemical sensors are made of sensitive elements that can convert chemical quantities such as the composition and concentration of chemical substances into electrical quantities. Biosensors are made using the characteristics of various organisms or biological substances to detect and identify chemical components in organisms.

3. Manufacturing process

4. According to the principle

Vibration sensor, humidity sensor, magnetic sensor, gas sensor, vacuum sensor, biological sensor, etc.

5. Output signal

Analog sensor: Convert the measured non-electrical quantity into an analog electrical signal.

Digital sensor: Convert the measured non-electrical quantity into a digital output signal (including direct and indirect conversion).

Pseudo-digital sensor: Convert the measured signal quantity into a frequency signal or a short-period signal output (including direct or indirect conversion).

Switch sensor: When a measured signal reaches a certain threshold, the sensor outputs a set low or high level signal accordingly.

Four or five commonly used sensors

Some commonly used sensors and their principles and applications are explained as follows:

(1), temperature sensor

This device collects information about temperature from a source and converts it into a form that other devices or humans can understand. The best example of a temperature sensor is a mercury-in-glass thermometer, which expands and contracts as temperature changes. The external temperature is the source of the temperature measurement, the observer looks at the position of the mercury to measure the temperature. There are two basic types of temperature sensors:

·Contact Sensor——This type of sensor requires direct physical contact with the object or medium being sensed. For example a thermometer.

·Non-contact sensor——This type of sensor does not require any physical contact with the object or medium being sensed. They monitor non-reflective solids and liquids, but are useless for gases due to their natural transparency. These sensors measure temperature using Planck's law. This law deals with heat radiated from a heat source to measure temperature.

Working principles and examples of different types of temperature sensors

(i) Thermocouples--they consist of two wires (each of a different homogeneous alloy or metal) joined at one end to form a measuring junction, which is open to the element under test. The other end of the wire terminates to the measurement device, where it forms the reference junction. Since the two junctions have different temperatures, current flows through the circuit and the resulting millivolts are measured to determine the junction temperature.

(ii) Resistance Temperature Detectors (RTDs) - These are thermal resistors that are manufactured to change resistance as temperature changes, and they are more expensive than any other temperature sensing device.

(iii) Thermistors – they are another type of resistor in which large changes in resistance are directly proportional to small changes in temperature.

(2), infrared sensor

The device emits or detects infrared radiation to sense specific phases in the environment. In general, thermal radiation is emitted by all objects in the infrared spectrum, and infrared sensors detect this radiation, which is invisible to the human eye.

(3), UV sensor

These sensors measure the intensity or power of incoming UV light. This electromagnetic radiation has longer wavelengths than x-rays, but is still shorter than visible light. An active material known as polycrystalline diamond is being used for reliable ultraviolet sensing, which detects environmental exposure to ultraviolet radiation.

(4), touch sensor

The touch sensor acts as a variable resistor based on the location of the touch. A touch sensor consists of a fully conductive substance such as copper, an insulating spacer material such as foam or plastic, and a partially conductive material.

(5), proximity sensor

Proximity sensors detect the presence of objects with hardly any contact points. Due to the lack of contact between the sensor and the object being measured and the lack of mechanical parts, these sensors have a long life and high reliability. Different types of proximity sensors are inductive proximity sensors, capacitive proximity sensors, ultrasonic proximity sensors, photoelectric sensors, Hall effect sensors, etc.

5. Advanced sensor technology

Sensor technology has a wide range of applications in manufacturing. The advanced technology is as follows:

1. Barcode identification - products sold on the market have a Universal Product Code (UPC), which is a 12-digit code. Five of the numbers represent the manufacturer and the other five represent the product. The first six digits are coded as light and dark bars. The first digit indicates the type of number system, and the second, parity, indicates the accuracy of the reading. The remaining six digits are shown with dark lines and dark lines, in the reverse order of the first six digits. The barcode is shown in the image below.

The barcode reader can manage different barcode standards, even without knowing the standard codes. The downside of barcodes is that if the barcode is covered with grease or dirt, it cannot be read by a barcode scanner.

Second, transponders - in the automotive sector, radio frequency devices are used in many cases. The transponder is hidden inside the key's plastic head, invisible to anyone. Insert the key into the ignition lock cylinder. When you turn the key, the computer sends a radio signal to the transceiver. The computer won't let the engine fire until the transponder responds to the signal. These transponders are powered by radio signals.

3. Electromagnetic identification of manufactured parts - this is similar to bar code technology, where data can be encoded on a magnetic strip. Using magnetic stripe technology, data can be read even if the code is hidden in grease or dirt.

Four, surface acoustic wave - this process is similar to radio frequency identification. Here, part identification is triggered by a radar-type signal and is transmitted over long distances compared to RF systems.

5. Optical Character Recognition - This is an automatic recognition technology that uses alphanumeric characters as a source of information. In the United States, mail processing centers use optical character recognition. They are also used in vision systems and speech recognition systems.

Register For Download

Kind reminder: Each user downloads once. If you need more information, please contact us

Submit