I. Overview
The W sensor is a new three-terminal all-digital sensor. The main difference from the sensors currently on the market is that its output is pulsed digital information that can be directly recognized by the computer, and its repetition frequency or pulse period is linearly related to the measured physical quantity.
The second principle of work
Any electronic sensor needs to change the measured physical quantity into an electrical parameter. This kind of transition is called a sensitive characteristic. Taking a temperature sensor using a PTC as a sensing element as an example to explain: When the ambient temperature increases, the resistance of the PTC thermistor increases. If we can design a RC oscillator, use the PTC thermistor as a part of the loop resistance, and it is required that when the PTC thermistor resistance increases, the repetition frequency of the oscillator output decreases. Adjust each parameter of the circuit so that within a certain interval, the characteristic curve of the thermistor coincides with the characteristic curve of the oscillation frequency of the oscillator. At this time, the temperature value sensed by the thermal PTC resistance can be represented by the frequency value. For example, 1200 Hz at -20°C, 1000 Hz at 0°C, and 800 Hz at +20°C. So on and so forth.
Three performance characteristics
1. The structure is simple: the traditional analog sensor, from the physical quantity to the digital quantity that the computer can identify, generally has to go through ten links. Take a capacitive humidity sensor as an example to illustrate the process: (1) the measured relative humidity value - humidity sensitive capacitor - (2) fixed frequency oscillator - (3) detector - (4) filter - (5) Integrator - (6) Amplifier - (7) Shaping Circuit - (8) Voltage and Current (4-20mA) Converter (VIC) - (9) Current Voltage (1-5V) Converter ( IVC) - (10) Analog to Digital Converter (ADC) - (11) Computer. A total of 10 links during this period. The conversion process of the W sensor is: (1) Relative humidity measured - sensor - (2) computer. Obviously, there is only one link. As shown in Figure 1. Each link has several components, each with error and drift. Less 8, 9 links, of course, measurement accuracy and stability should be improved. Secondly, there are material costs and commissioning fees for each link. The low cost of the link is of course low. And the operation is simple, easy to maintain, durable, easy to promote and apply.
2. Strong anti-interference ability: The biggest characteristic of the analog sensor is to change the measured physical quantity to voltage first and then change the voltage to digital. External interference signals are mostly in the form of voltage. The interference voltage and the measured voltage are easily superimposed or subtracted, causing confusion. The W sensor directly changes the physical quantity into frequency, and the information is stored in the frequency, so it is not influenced by the voltage interference signal.
3. It is advantageous for distance transmission without line resistance compensation. The distance measurement accuracy is the same between the near and far distances: the measurement information of the analog sensor is stored in the output voltage, and the line resistance will attenuate the voltage. Therefore, resistance compensation is often needed. These resistances will Loss of measurement accuracy due to errors, temperature effects, and drift. W sensor will be measured in the information contained in the frequency, not affected by the line resistance, it is conducive to long-distance transmission.
4. No need to connect any external device, can directly interface with the computer: Because the information output by the W sensor is the pulse frequency, it can be expressed by the number of 0, 1 or the time of the pulse cycle. The internal clock of the computer is very easy to identify, thus saving a lot of assembly The process of debugging.
The W sensor is a new three-terminal all-digital sensor. The main difference from the sensors currently on the market is that its output is pulsed digital information that can be directly recognized by the computer, and its repetition frequency or pulse period is linearly related to the measured physical quantity.
The second principle of work
Any electronic sensor needs to change the measured physical quantity into an electrical parameter. This kind of transition is called a sensitive characteristic. Taking a temperature sensor using a PTC as a sensing element as an example to explain: When the ambient temperature increases, the resistance of the PTC thermistor increases. If we can design a RC oscillator, use the PTC thermistor as a part of the loop resistance, and it is required that when the PTC thermistor resistance increases, the repetition frequency of the oscillator output decreases. Adjust each parameter of the circuit so that within a certain interval, the characteristic curve of the thermistor coincides with the characteristic curve of the oscillation frequency of the oscillator. At this time, the temperature value sensed by the thermal PTC resistance can be represented by the frequency value. For example, 1200 Hz at -20°C, 1000 Hz at 0°C, and 800 Hz at +20°C. So on and so forth.
Three performance characteristics
1. The structure is simple: the traditional analog sensor, from the physical quantity to the digital quantity that the computer can identify, generally has to go through ten links. Take a capacitive humidity sensor as an example to illustrate the process: (1) the measured relative humidity value - humidity sensitive capacitor - (2) fixed frequency oscillator - (3) detector - (4) filter - (5) Integrator - (6) Amplifier - (7) Shaping Circuit - (8) Voltage and Current (4-20mA) Converter (VIC) - (9) Current Voltage (1-5V) Converter ( IVC) - (10) Analog to Digital Converter (ADC) - (11) Computer. A total of 10 links during this period. The conversion process of the W sensor is: (1) Relative humidity measured - sensor - (2) computer. Obviously, there is only one link. As shown in Figure 1. Each link has several components, each with error and drift. Less 8, 9 links, of course, measurement accuracy and stability should be improved. Secondly, there are material costs and commissioning fees for each link. The low cost of the link is of course low. And the operation is simple, easy to maintain, durable, easy to promote and apply.
2. Strong anti-interference ability: The biggest characteristic of the analog sensor is to change the measured physical quantity to voltage first and then change the voltage to digital. External interference signals are mostly in the form of voltage. The interference voltage and the measured voltage are easily superimposed or subtracted, causing confusion. The W sensor directly changes the physical quantity into frequency, and the information is stored in the frequency, so it is not influenced by the voltage interference signal.
3. It is advantageous for distance transmission without line resistance compensation. The distance measurement accuracy is the same between the near and far distances: the measurement information of the analog sensor is stored in the output voltage, and the line resistance will attenuate the voltage. Therefore, resistance compensation is often needed. These resistances will Loss of measurement accuracy due to errors, temperature effects, and drift. W sensor will be measured in the information contained in the frequency, not affected by the line resistance, it is conducive to long-distance transmission.
4. No need to connect any external device, can directly interface with the computer: Because the information output by the W sensor is the pulse frequency, it can be expressed by the number of 0, 1 or the time of the pulse cycle. The internal clock of the computer is very easy to identify, thus saving a lot of assembly The process of debugging.
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