its常用的传感器类型

1.电阻式传感器

电阻式传感器是将被测量，如位移、形变、力、加速度、湿度、温度等这些物理量转换式成电阻值这样的一种器件。主要有电阻应变式、压阻式、热电阻、热敏、气敏、湿敏等电阻式传感器件。

2.变频功率传感器

变频功率传感器通过对输入的电压、电流信号进行交流采样，再将采样值通过电缆、光纤等传输系统与数字量输入二次仪表相连，数字量输入二次仪表对电压、电流的采样值进行运算，可以获取电压有效值、电流有效值、基波电压、基波电流、谐波电压、谐波电流、有功功率、基波功率、谐波功率等参数。

3.称重传感器

称重传感器是一种能够将重力转变为电信号的力→电转换装置，是电子衡器的一个关键部件。

能够实现力→电转换的传感器有多种，常见的有电阻应变式、电磁力式和电容式等。电磁力式主要用于电子天平，电容式用于部分电子吊秤，而绝大多数衡器产品所用的还是电阻应变式称重传感器。电阻应变式称重传感器结构较简单，准确度高，适用面广，且能够在相对比较差的环境下使用。因此电阻应变式称重传感器在衡器中得到了广泛地运用。

4.电阻应变式传感器

传感器中的电阻应变片具有金属的应变效应，即在外力作用下产生机械形变，从而使电阻值随之发生相应的变化。电阻应变片主要有金属和半导体两类，金属应变片有金属丝式、箔式、薄膜式之分。半导体应变片具有灵敏度高(通常是丝式、箔式的几十倍)、横向效应小等优点。

5.压阻式

压阻式传感器是根据半导体材料的压阻效应在半导体材料的基片上经扩散电阻而制成的器件。其基片可直接作为测量传感元件，扩散电阻在基片内接成电桥形式。当基片受到外力作用而产生形变时，各电阻值将发生变化，电桥就会产生相应的不平衡输出。

用作压阻式传感器的基片(或称膜片)材料主要为硅片和锗片，硅片为敏感材料而制成的硅压阻传感器越来越受到人们的重视，尤其是以测量压力和速度的固态压阻式传感器应用最为普遍。

6.热电阻传感器

热电阻测温是基于金属导体的电阻值随温度的增加而增加这一特性来进行温度测量的。热电阻大都由纯金属材料制成，目前应用最多的是铂和铜，此外，已开始采用镍、锰和铑等材料制造热电阻。

热电阻传感器主要是利用电阻值随温度变化而变化这一特性来测量温度及与温度有关的参数。在温度检测精度要求比较高的场合，这种传感器比较适用。较为广泛的热电阻材料为铂、铜、镍等，它们具有电阻温度系数大、线性好、性能稳定、使用温度范围宽、加工容易等特点。用于测量-200℃～+500℃范围内的温度。

7.激光传感器

利用激光技术进行测量的传感器。它由激光器、激光检测器和测量电路组成。激光传感器是新型测量仪表，它的优点是能实现无接触远距离测量，速度快，精度高，量程大，抗光、电干扰能力强等。

In addition to improvements in chip performance, the shell packaging technology is also a great breakthrough, IR inversion in the development of field-effect transistor, also known as "FlipFET" on the basis of this year introduced the DirectFET, as shown in Figure 6. Its source and gate inversion result can be directly welded in the printed circuit board, the drain at the top of the weld metal in its shell, if necessary, by the radiator or direct contact with the equipment enclosure. DirectFET size equivalent to the traditional SO-8 plastic (plastic with an area of about 4x5 mm2) shell. In such a small device, the first structure of a double-sided cooling. It is a lead frame, no-lead solder joints of the device, it brought about a series of advantages: it's non-resistor chip package (DFPR) is only 0. 1mW, device thickness of only 0. 7mm, resistance and parasitic inductance have dropped significantly. Such characteristics make it especially suitable for the above-mentioned computer of the latest generation of CPU. In the multi-phase circuits, each with only two of 30 security DirectFET can transfer current. Increase its current rate of 400 per delicate security, the working frequency of 1-2 MHz.

Secondly, you must be focused on power semiconductor devices in the IC direction: as a result of the development of MOSFET and IGBT, and their matching to provide a trigger signal power integrated circuit PIC (Power IC) have also developed rapidly. At that time, also known as MOS gate drive MGD (MOS Gate Driver) or control integrated circuit CIC (Control IC). With the expansion of the scope of application: such as motor drives, lighting, various power supply and so on, CIC of the cultivars have been rapidly increasing. These CIC in the development process

And gradually from a simple function to trigger the special needs of a wide range of applications development. PIC is the earliest that can be used in high voltage IC, therefore, also known as high-voltage IC (HVIC). However, many applications such as communications, computers, portable power supply and so on, they do not require high voltage, but demand for the special needs of the development of application specific integrated circuit. Because of their combination and application of power semiconductor devices, we have the power to include them in a class of semiconductor devices. So now the power semiconductor devices in the family, there are many integrated circuits. Many of these power devices with integrated circuits inside, some outside while the separation of power devices. Judging from this point, the limits of power and microelectronics has become increasingly blurred. If a large number of computer applications in power modulation device voltage LDO (Low Drop Out) is one example. It does not belong to switch applications.

As a result of a large number of integrated circuits into the power semiconductor devices, which consider the power semiconductor integrated circuits and devices to do the same in the chip or device on the development of the natural line of thought. Done in the same chip, the original is the concept of power integrated circuits, but their power often relatively small. Done in the same package, easy to increase power capacity, a number of passive components is also possible to join, here often called multi-chip module (MCM).

IR last year iPOWIR developed is a typical multi-chip module. It will power devices to control the use of integrated circuits, or in combination with pulse-width modulation (PWM) integrated circuit, according to the needs of power supply design, using BGA packaging technology portfolio in the same device (as shown in Figure 7) . Multi-chip device that greatly simplifies the power supply design staff. Components reduces the number and percentage of the area, there has been a lot of performance improvement. iPOWIR development is considered DC-DC conversion of the future. But, in fact, a wide range of applications in other fields, as long as the requirements of further integration, MCM structure and will there will be more and more. Therefore, it is the power semiconductor devices important direction of development.

In the above presentation, the development of MOSFET has been referred to as 4C industry provides an important foundation. 4C industries which, at present it is the most active direction of the product. We can understand: in the communications, computer, consumer electronics and automotive development, will require many, many close contacts and IC of all types of power semiconductor devices. Each of these aspects can be used to introduce a lot of space. Not detailed here.

Add: Conclusion

To sum up, the power semiconductor devices the past few years, constantly changed a lot. So can no longer look at a fixed vision of the development of power semiconductor devices. For example, not simply thyristor power semiconductor devices and an equal sign painting, or drawing an equal sign and discrete devices. Must not power semiconductor devices and microelectronics artificially separated, it seems only semiconductor microelectronics. These will impede the development of power semiconductor devices, in the long run will hinder the development of microelectronic devices. Development strategy in order to avoid the power semiconductor devices as a simple process only to be completed on the low-tech products. And the preferential policies available only to integrated circuit industry. China has not been very good to the development of modern power semiconductor devices, the lack of modern power semiconductor devices is a comprehensive understanding of the factors I am afraid. Information technology to stimulate industrialization in the wave, it is imperative that different semiconductor devices have a balanced development.

Conclusion

To sum up, the power semiconductor devices the past few years, constantly changed a lot. So can no longer look at a fixed vision of the development of power semiconductor devices. For example, not simply thyristor power semiconductor devices and an equal sign painting, or drawing an equal sign and discrete devices. Must not power semiconductor devices and microelectronics artificially separated, it seems only semiconductor microelectronics. These will impede the development of power semiconductor devices, in the long run will hinder the development of microelectronic devices. Development strategy in order to avoid the power semiconductor devices as a simple process only to be completed on the low-tech products. And the preferential policies available only to integrated circuit industry. China has not been very good to the development of modern power semiconductor devices, the lack of modern power semiconductor devices is a comprehensive understanding of the factors I am afraid. Information technology to stimulate industrialization in the wave, it is imperative that different semiconductor devices have a balanced development.

一楼没看清问题。为公平起见，我先把一楼的回答翻译成中文，加上我的评语【在黑括号内】，然后再给出我的回答。取决于你要解什么问题【没错】。如果我们只考虑自由费米子，那么狄拉克方程具有洛仑兹对称【胡言乱语。谁问＂自由费米子＂了？】。它的表象分类为H和自旋【H里不包含自旋？你上课睡着了吧？】。因此，我们选择这些变量【自旋是个变量，H可不是】。而且狄拉克方程具有平移不变性，所以可以用动量来表示其解【文不对题。半导体器件里几乎没有平移不变的问题】。当有相互作用时，应该用别的，如中心力问题中用角动量【越说离题越远。半导体里哪来的中心力问题？】。当耦合到电磁场时，事实上还有一个量子数，就是电荷【错！电荷在固体里是个常数，只有在量子场论里才是量子数】。还有，如果我们考虑电子的弱相互作用，那么还有同位旋【一楼这是在忽悠谁呢？半导体物理要考虑同位旋，那你是不是坐火箭上下楼啊？】正确答案：在玻耳兹曼方程中，电子的分布函数有七个变量：三个坐标、三个动量分量、一个时间变量。如果是稳态过程，时间变量可以去掉。即使是瞬态问题，时间也不是粒子的自由度。所以从玻耳兹曼方程讲，电子应该有六个自由度。从热力学意义上讲，每个动量分量都是相应方向坐标分量的共轭变量，所以只有三个自由度。除非做自旋电子学，否则自旋自由度可以不考虑。简言之：玻耳兹曼方程六个自由度，热力学三个自由度。

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