外文翻译(供热站温度实时监测)

1 Heating temperature and pressure test Thermistors are inexpensive, easily-obtainable temperature sensors. They are easy to use and adaptable. Circuits with thermistors can have reasonable outout voltages - not the millivolt outputs thermocouples have. Because of these qualities, thermistors are widely used for simple temperature measurements. Theyre not used for high temperatures, but in the temperature ranges where they work they are widely used. Thermistors are temperature sensitive resistors. All resistors vary with temperature, but thermistors are constructed of semiconductor material with a resistivity that is especially sensitive to temperature. However, unlike most other resistive devices, the resistance of a thermistor decreases with increasing temperature. Thats due to the properties of the semiconductor material that the thermistor is made from. For some, that may be counterintuitive, but it is correct. Here is a graph of resistance as a function of temperature for a typical thermistor. Notice how the resistance drops from 100 kW, to a very small value in a range around room temperature. Not only is the resistance change in the opposite direction from what you expect, but the magnitude of the percentage resistance change is substantial. Temperature Sensor - The Thermocouple You are at: Elements - Sensors - Thermocouples Return to Table of Contents A thermocouple is a junction formed from two dissimilar metals. Actually, it is a pair of junctions. One at a reference temperature (like 0 oC) and the other junction at the temperature to be measured. A temperature difference will cause a voltage to be developed that is temperature dependent. (That voltage is caused by something called the Seebeck effect.) Thermocouples are widely used for temperature measurement because they are inexpensive, rugged and reliable, and they can be used over a wide temperature range. 2 In particular, other temperature sensors (like thermistors and LM35 sensors) are useful around room temperature, but the thermocouple can The Thermocouple Why Use thermocouples To Measure Temperature? They are inexpensive. They are rugged and reliable. They can be used over a wide temperature range. What Does A Thermocouple Look Like? Here it is. Note the two wires (of two different metals) joined in the junction. What does a thermocouple do? How does it work? The junction of two dissimilar metals produces a temperature dependent voltage. For a better description of how it works, click here. How Do You Use A Thermocouple? You measure the voltage the thermocouple produces, and convert that voltage to a temperature reading. It may be best to do the conversion digitally because the conversion can be fairly nonlinear. Things You Need To Know About Thermocouples A junction between two dissimilar metals produces a voltage. In the thermocouple, the sensing junction - produces a voltage that depends upon temperature. Where the thermocouple connects to instrumentation - copper wires? - you have two more junctions and they also produce a temperature dependent voltage. Those junctions are shown inside the yellow oval. When you use a thermocouple, you need to ensure that the connections are at some standard temperature, or you need to use an electronically compensated system that takes those voltages into account. If your thermocouple is connected to a data acquisition system, then chances are good that you have an electronically compensated system. Once we obtain a reading from a voltmeter, the measured voltage has to be converted to temperature. The temperature is usually expressed as a polynomial function of the measured voltage. Sometimes it is possible to get a decent linear approximation over a limited temperature range. There are two ways to convert the measured voltage to a temperature reading. Measure the voltage and let the operator do the calculations. Use the measured voltage as an input to a conversion circuit - either analog or digital. Let us look at some 3 other types of base-metal thermocouples. Type T thermocouples are widely used as are type K and Type N. Type K (Ni-Cr/Ni-Al) thermocouples are also widely used in the industry. It has high thermopower and good resistance to oxidation. The operating temperature range of a Type K thermocouple is from -269 oC to +1260 oC. However, this thermocouple performs rather poorly in reducing atmospheres. Type T (Cu/Cu-Ni) thermocouples can be used in oxidizing of inert atmospheres over the temperature range of -250 oC to +850 oC. In reducing or mildly oxidizing environments, it is possible to use the thermocouple up to nearly +1000 oC. Type N (Nicrosil/Nisil) thermocouples are designed to be used in industrial environments of temperatures up to +1200 oC. A polynomial equation used to convert thermocouple voltage to temperature (oC) over a wide range of temperatures. We can write the polynomial as: The coefficients, an are tabulated in many places. Here are the NBS polynomial coefficients for a type K thermocouple. (Source: T. J. Quinn, Temperature , Academic Press Inc.,1990) Type K Polynomial Coefficients n an 0 0.226584602 1 24152.10900 2 67233.4248 3 2210340.682 4 -860963914.9 5 4.83506x1010 6 -1.18452x1012 7 1.38690x1013 8 -6.33708x1013 What If The Surrounding Temperature Exceeds Limits? There are really no thermocouples that can withstand oxidizing atmospheres for temperatures above the upper limit of the platinum-rhodium type thermocouples. We cannot, therefore, measure temperature in such high temperature conditions. Other options for measuring extremely high temperatures are radiation or the noise pyrometer. For non-oxidizing atmospheres, tungsten-rhenium based thermocouples shows good performance up to +2750 oC. They can be used, for a short period, in temperatures up to +3000 oC. The selection of the types of thermocouple used for low temperature sensing is primarily based on materials of a thermocouple. In addition, thermopower at low temperatue is 4 rather low, so measurement of EMF will be proportionally small as well. More Facts On Various Thermocouple Types A variety of thermocouples today cover a range of temperature from -250 oC to +3000 oC. The different types of thermocouple are given letter designations: B, E, J, K, R, S, T and N Types R,S and B are noble metal thermocouples that are used to measure high temperature. Within their temperature range, they can operate for a longer period of time under an oxidizing environment. Type S and type R thermocouples are made up of platinum (Pt) and rhodium (Rh) mixed in different ratios. A specific Pt/Rh ratio is used because it leads to more stable and reproducible measurements. Types S and R have an upper temperature limit of +1200 oC in oxidizing atmospheres, assuming a wire diameter of 0.5mm. Type S and type R thermocouples are made up of platinum (Pt) and rhodium (Rh) mixed in different ratios. A specific Pt/Rh ratio is used because it leads to more stable and reproducible measurements. Types S and R have an upper temperature limit of +1200 oC in oxidizing atmospheres, assuming a wire diameter of 0.5mm. Type B thermocouples have a different Pt/Rh ratio than Type S and R. It has an upper temperature limit of +1750 oC in oxidizing atmospheres. Due to an increased amount of rhodium content, type B thermocouples are no quite so stable as either the Type R or Type S. Types E, J, K, T, and N are base-metal thermocouples that are used for sensing lower temperatures. They cannot be used for sensing high temperatures because of their relatively low melting point and slower failure due to oxidation. Type B thermocouples have a different Pt/Rh ratio than Type S and R. It has an upper temperature limit of +1750 oC in oxidizing atmospheres. Due to an increased amount of rhodium content, type B thermocouples are no quite so stable as either the Type R or Type S. we will look into some differences between different base-metal thermocouples. Type E (Ni-Cr/Cu-Ni) thermocouples have an operating temperature range from -250 oC to +800 oC. Their use is less widespread than other base-metal 5 thermocouples due to its low operating temperature. However, measurements made by a Type E have a smaller margin of error. 1000 hours of operation in air of a Type E thermocouple at +760 oC, having 3mm wires, shold not lead to a change in EMF equivalent to more than +1 oC. Type J (Fe/Cu-Ni) thermocouples are widely used in industry due to their high thermopower and low cost. This type of thermocouple has an operating temperature range from 0 oC to +760 oC. Links to Related Lessons Temperature Sensors Thermistors Thermocouples LM35s Other Sensors Strain Gages Temperature Sensor Laboratories Return to Table of Contents Experiments With Temperature Sensors - Data Gathering Measuring temperature is the most common measurement task. There are numerous devices available for measuring temperature. Many of them are built using one of these common sensors. Thermistor Thermocouple LM35 Integrated Circuit Temperature Sensor You can get more information about these sensors by clicking the links above. Laboratory The purpose of this laboratory is to get time response data for the three sensors you were introduced to labs week. Here are links to LabVIEW programs you can use. NTempsHydra.vi - to measure temperature from the Hydra. NVoltsHydra.vi - to measure voltage from the Hydra. ResetHydra.vi - A sub-vi you need to reset the Hydra. 1Temp.vi - A sub-vi that will take one temperature measurement on the Hydra. 1VoltHydra.vi - A sub-vi that will take one voltage measurement on the Hydra. You should have all the files above on your desktop. You can click on each link and save to the desktop, or you can find the NMeas folder in my public space and copy the entire folder to the desktop (best). You only need to double click the NTemps or NVolts files to start and run them in LabVIEW - but they have to be taken out of the network folder! Once you have the files together in a single folder on 6 your desktop, Start NTempsHydra.vi to measure temperature using the thermocouple attached to terminals 21 (yellow lead) and 22 (red lead). Note that these terminals (21 and 22) are the connections for channel 1 for the Hydra. (For example, if you were doing a manual temperature reading using the front panel, you would need to set to channel 1.) You need to connect the yellow lead of the thermocouple to the top connector for Channel #1 (Terminal #21) and the red lead of the thermocouple to the bottom connector (ground?) for Channel #1 (Terminal #22). Both of those connections are made to the connector strip on the top of the Hydra Data Acquisition Unit. Start NVoltsHydra.vi to measure voltages using the LM35 and the voltage divider circuit for the thermistor. Both sets of measurements should be taken from the front panel connection points on the Hydra. For both the LM35 and the thermistor circuit, you need to supply 5v to the circuit board. In your lab notebook record any circuitry you use, and any pertinent points regarding the equipment you use. Note any other features of each sensor that will help you for your project or make things more difficult. Do the following: Connect each sensor. Here are links to using each sensor in a measurement. Thermocouples LM35s Thermistors For each sensor you need to get data in two situations: As the sensor heats up (rising time constant behavior) As the sensor cools down to ambient temperature (decaying time constant behavior) That data should be stored in a computer file. Use a different, understandable name for each file. The program will prompt you for a file name. Suggested file names are things like ThermistorUp.txt, etc. Before you leave lab be sure that you can bring your data up in Excel (to test that you have a good data file) and that you can plot the data to see that it looks like what you expect. Estimate the following for each sensor. The time it will take for the sensor to get within 1oC when the sensor is in good thermal contact with the temperature environment being measured and the temperature sensor starts at 25 oC and goes to 50 oC. (That means to 7 measure the time it takes to get to between 49 oC and 51 oC.) The time it will take for the sensor to get within 1oC of the final value when the sensor is in air at a constant temperature and the temperature sensor starts at 25oC and goes to 50oC. In other words, when will the temperature sensor reach 49oC? The time it will take for the sensor to get within 0.1oC for the two situations above. (i.e., between 49.9 oC and 50.1 oC.) The time it will take for the sensor to get within 1oC when the sensor is in good thermal contact with the temperature environment being measured and the temperature sensor starts at 50 oC and goes to 25 oC. Explain why there is a difference in the speed of the response in the various situations above. Your report should show calculations for the time constant(s) for each device, and should show the results using the three methods. Tabular presentation of the results is best. Finally, you should - as best possible - explain your results. Why would the time constant be different going up and going down. 8 供热站温度压力实时检测 热敏电阻很便宜，易于得到的温度传感器。它们易于使用和适应性。与热敏电阻的电路可以有合理 outout电压 - 而不是产出热电偶毫伏的。 由于这些优势，热敏电阻广泛用于简单的温度测量。 它们不是用于高温，但在他们的工作温度范围在那里，他们被广泛使用。 热敏电阻温度敏感电阻器。 所有的电阻随温度，但热敏电阻的半导体材料建造，是一个电阻对温度特别敏感。但是，与大多数其他电阻器，热敏电阻的一个随温度降低。 这是由于半导体材料制成的热敏电阻的特性。一些人认为，这可能是违反直觉，但它是正 确的。 这里是一个电阻作为温度函数的图像为一典型的热敏电阻。请注意阻力从 100千瓦下降到一个很小的值在 1左右房间温度范围。 不仅是从你期望相反的方向电阻的变化，但其电阻变化率的幅度是可观的。 温度传感器 - 热电偶您现在的位置：元素 - 传感器 - 热电偶返回目录热电偶表是由两个不同的金属组成的交界处。 其实，这是一个路口对。一位在参考温度 0 oC的像（）和其他交界处的温度进行测量。 阿温差会引起电压要发展是温度而定。 （该电压是由一些被称为塞贝克效应引起的。）热电偶广泛用于温度测量，因为它们价格便宜，坚固可靠 ，而且可以在很宽的温度范围内使用。特别是，其他如热敏电阻温度传感器和传感器 LM35（）周围室温有用的，但为什么热电偶热电偶可以使用热电偶测量温度？ 他们是廉价的。他们是坚固，可靠。它们可用于在很宽的温度范围。热电偶是什么样子？在这里。注意两条线两种不同的金属（）参加了路口。热电偶是什么呢？它是如何工作的？两种不同的金属交界处产生电压的温度依赖性。对于如何更有效的描述，请点击这里。你是如何利用热电偶？您测量热电偶产生的电压，并转换成的电压，温度读数。这可能是最好的进行转换，因为转换的数字可以相当非线性的。事情你 需要知道关于热电偶的两种不同金属之间的交界处产生电压。在热电偶，传感交界处 - 产生的电压时的温度而定。凡热电偶连接到仪器 - 铜导线？ - 你有两个路口，同时也产生电压的温度依赖性。显示这些路口内的黄色椭圆形。当您使用热电偶时，您需要确保连接是在一些标准的温度，或者你需要使用一个电子补偿系统，考虑到这些电压。如果您的热电偶连接到数据采集系统，然后有很好的机会，你有一个电子补偿制度。一旦我们获得了由电压表读数，测得的电压必须转换为温度。温度通常表示为多项式函数的测量电压。有时有可能获得超过一有限的温度范围内 像样的线性近似。有两种方法来测量电压转换为温度读数。测量电压，让经营者做计算。以此作为一个转换电路 - 无论是模 9 拟或数字输入电压的测量。让我们看看基本金属热电偶一些其他类型。 T型热电偶被广泛用作是 K型和 K型型北路（ Ni-Cr/Ni-Al）热电偶也广泛应用在工业中使用。它具有较高的热电势和良好的抗氧化作用。一个 K型热电偶的工作温度范围为摄氏从 -269 1260 。然而，这种热电偶表现不佳而在减少大气。 T型（铜 /铜镍）热电偶可以在惰性气氛氧化以上的 -250 oC的温度范围为 850 oC的使用。在减少或轻度氧 化环境中，可以使用热电偶至接近 1000 。 N型（ Nicrosil / Nisil）热电偶的设计可在温度高达 1200 oC的工业环境下使用。一个多项式方程用于热电偶电压转换温度（ ）以上的温度范围。我们可以写多项式为：系数，一个是在许多地方表列。下面是一个 K型热电偶国家统计局多项式系数。 （来源：勺奎恩，温度，学术出版社有限公司， 1990年） K型 多项式系数 1 1 0 0.226584602 24152.10900 2 67233.4248 3 2210340.682 4 -860963914.9 5 4.83506x1010 6 1.18452x1012 7 1.38690x1013 8 6.33708x1013什么如果周边温度超过限制？真的有没有能抵御氧化热电偶以上的铂铑热电偶型大气温度的上限。我们不能，因此，在如此高的温度测量环境温度。测量温度非常高辐射或其他选项的噪音高温计。对于非氧化性气氛，钨铼热电偶具有良好的性能高达 2750 。他们可以使用，很短的时间，在温度高达 3000 。作者：热电偶温度传感器采用低类型的选择主要是基于一个热电偶材料。此外，在低受热热电相当低，所以将 EMF测量比例太小了。更多的 事实在不同类型的热电偶热电偶品种涵盖了从今天 -250 oC的温度范围为 3000 。不同类型的热电偶，给出英文字母代号：二，电子，强，钾，俄，西， T和 N型度 R， S和 B是贵金属，用于测量高温热电偶。其温度范围内，他们可以经营了一段较长时间的氧化环境下。 S型和 R型热电偶是由白金注册（铂）和铑（铑）在不同的比例混合。一个具体的铂 /铑比为使用，因为它会导致更加稳定和可重复性测量。 S型和 R在氧化气氛的 1200 oC的温度的上限，假设一个线径为 0.5mm。 S型和 R型热电偶是由白金注册（铂）和铑（铑）在不同的比例混合 。一个具体的铂 /铑比为使用，因为它会导致更加稳定和可重复性测量。 S型和 R在氧化气氛的 1200 oC的温度的上限，假设一个线径为 0.5mm。 B型热电偶具有不同的 Pt / S型和 R比它在氧化气氛的 1750 oC的温度的上限 Rh的比例。由于对铑含量， B型热电偶增加额没有这么稳定的任何类型的 R型或 E型南，强，钾， T和 N是基本金属可用于检测用热电偶温度较低。它们不能用于检测由于其相对较低的熔点和慢衰竭的高温氧化。 B型热电偶具有不同的 Pt / S型和 R比它在氧化气氛的 1750 oC的温度的上限 Rh的比例。由于对铑 含量， B型热电偶增加额没有这么稳定的无论是 R型或类型号我们会研究不同基本金属热电偶存在一些分歧。 E型（ Ni-Cr/Cu-Ni）热电偶从 -250 oC的工作温度范围 10 为 800 。它们的使用小于其他基本金属热电偶由于其较低的工作温度普遍。不过，测量了由 E型有小幅度的误差。 1000小时的行动中 E型热电偶在 760 oC的空气，有 3毫米电线， shold不会导致在电磁场等效变化超过 1 。 J型（铁 /铜镍）热电偶广泛应用于工业，由于其高热电，成本低。这种类型的热电偶从 0 到 +760 oC的工作温度范围。链接到温度传感器 热敏电阻热电偶相关教训 LM35s应变计温度传感器其他传感器实验室返回目录 随着温度传感器实验 - 数据采集测量温度是最常见的测量任务。有许多设备可以测量温度。他们中许多人都使用这些共同传感器之一。热敏电阻热电偶温度传感器 LM35集成电路您可以通过点击获得更多关于上面的链接这些传感器的信息。实验室这个实验室的目的是能为你介绍了三个星期，以实验室传感器时间响应数据。以下是链接到 LabVIEW的程式可以使用。 NTempsHydra.vi - 测量温度从九头蛇。 NVoltsHydra.vi - 衡量从九头蛇 电压。 ResetHydra.vi -