New Development trend of Intelligent temperature Sensor


New Development trend of Intelligent temperature Sensor

After the 21st century, the intelligent temperature sensor is developing rapidly in the direction of high precision, multi-function, bus standardization, high reliability and security, development of virtual sensor and network sensor, and the development of a single-chip temperature measuring system.

1. Improving the accuracy and resolution of temperature measurement

In the mid-1990s, the first intelligent temperature sensor was introduced, and the 8-bit A/ D converter is adopted. The temperature measurement accuracy is low and the resolution can only reach 1 ° C. At present, a variety of high-precision and high-resolution intelligent temperature sensors have been introduced in the world. The 9-12-bit A/ D converter is used, and the resolution is generally in the range of 0.5-0.0625 ° C. The DS1624 high-resolution intelligent temperature sensor developed by the DALLAS semiconductor company in the United States can output 13-bit binary data with a resolution of up to 0.03125 ° C. In order to improve the conversion rate of the multichannel intelligent temperature sensor, the high-speed successive approximation A/ D converter is adopted in the chip. Taking the AD7817 type 5-channel intelligent temperature sensor as an example, the conversion time of the remote sensor is 27us and 9us, respectively.

2. Add test function

The testing function of the new intelligent temperature sensor is also increasing. For example, DS1629 single-wire intelligent temperature sensor adds real-time calendar clock (RTC), to make its function more perfect. DS1624 also adds storage function, which can store user's short message by using 256 bytes E2PROM memory inside the chip. In addition, intelligent temperature sensors are developing from single channel to multichannel, which creates good conditions for the research and development of multichannel temperature measurement and control system.

The energy temperature controller is developed on the basis of intelligent temperature sensor. Typical products are DS1620,DS1623,TCN75,LM76,MAX6625. The intelligent temperature controller is adapted to all kinds of micro controllers to form an intelligent temperature control system, and they can also work independently from the micro-controller and form a temperature control instrument by themselves.

3. Standardization and Standardization of bus Technology

At present, the bus technology of intelligent temperature sensor has also been standardized and standardized. The main buses used are single-wire (1-Wire) bus, I2C bus, SMBus bus and spI bus. As a slave, the temperature sensor can communicate with the host computer through the special bus interface.

4. Reliability and safety design

Most of the traditional A ≤ D converters use integral or successive comparison conversion technology, which has low noise tolerance and poor ability to suppress aliasing noise and quantitative noise. The new intelligent temperature sensor (such as TMP03/04,LM74,LM83) generally adopts high performance Σ-Δ A D converter, which can convert analog signal into digital signal with high sampling rate and low sampling resolution, and then improve effective resolution by using oversampling, noise shaping and digital filtering technology. Σ-Δ A D converter can not only filter out quantitative noise. Moreover, the accuracy of the peripheral components is low. Because of the digital feedback mode, the misalignment voltage and zero drift of the comparer will not affect the conversion accuracy of temperature. The intelligent temperature sensor has the advantages of strong ability to suppress serial mode interference, high resolution, good linearity and low cost.

In order to avoid malfunction when the temperature control system is disturbed by noise, a programmable``f Aultqueue'' counter is provided in the interior of intelligent temperature sensors such as AD7416/7417/7817, LM75/76, MAX6625/6626, which is specially used to set the number of times that the measured temperature value exceeds the upper and lower limit. The interrupt end can only be triggered if the measured temperature continuously exceeds the upper limit or is lower than the lower limit and reaches or exceeds the set number of times n(n=1~4). If the number of failures fails to meet the above conditions or the fault does not occur continuously, the fault counter is reset without triggering the interrupt terminal. This means that, assuming n=3, no accidental noise interference will affect the normal operation of the temperature control system.

The newly developed intelligent temperature sensor (such as MAX6654,LM83) also adds the sensor fault detection function, which can automatically detect the open circuit or short circuit fault of the external transistor temperature sensor (also known as remote sensor). Max6654 also has the choice of "parasitic impedance cancellation" (PArAsitic ResistAnce CAncellAtion, abbreviated as prc) mode, which can offset the temperature measurement error caused by the lead impedance of the remote sensor, even if the lead impedance reaches 100ohm. Nor will it affect the measurement accuracy. Remote sensor leads can use ordinary twisted-pair wire or twisted-pair wire with shield layer.

5.Virtual temperature Sensor and Network temperature Sensor

(1)Virtual sensor

The virtual sensor is based on sensor hardware and computer platform and is developed by software development. The calibration and calibration of the sensor can be completed with the software to achieve the best performance index. Recently, U.S. B & K has developed a software-based TEDS-based virtual sensor featuring a unique product serial number per sensor and a floppy disk that stores data on the sensor to be calibrated. When in use, the sensor is connected to a computer through a data collector, the product serial number of the sensor is first input from a computer, the related data is read out from the magnetic disk, and then the inspection of the sensor, the reading of the sensor parameters, the sensor setting and the recording operation are automatically completed.

(2)Network temperature sensor

The network temperature sensor is a new generation of smart sensors that include a digital sensor, a network interface, and a processing unit. The digital sensor first converts the measured temperature into a digital quantity and then sends it to the micro-controller for data processing. And finally, the measurement result is transmitted to the network so as to realize data exchange and resource sharing among the sensors, between the sensor and the actuator, between the sensor and the system, and when the sensor is replaced, the calibration and the calibration are not required, so that the "Plug & Play" can be realized, so that the user is greatly facilitated.

6.Single chip temperature measurement system

System On Chip is a science and technology product in the 21st century. It is the integration of a system or sub-system on the chip, and the integration level will be as high as 108-109 elements/ pieces, which will bring an epoch-making progress to the IC industry and the IC application. The predictions made by the Semiconductor Industry Association (SIA) for the integration of the system are presented in Table 1. At present, some famous IC manufacturers in the world have started to develop a single-chip temperature measuring system, which is believed to be ready in the near future.

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