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数字温度计
With the easy availability of inexpensive digital multimeters, and integrated circuit temperature sensors, it is now very easy to build a sensitive and accurate digital thermometer that can be used for many experiments around the house or in the amateur laboratory.与容易获得的便宜的数字多用表,和集成电路温度感应器,现在很容易建立了一个敏感的和准确的数字温度计,可以用于许多试验在房子里或者在业余实验室。 There are two tenperature sensors that make this particulary easy -- the LM34 and the LM35. 有两个流动性传感器使得这尤其容易——LM34和LM35。These are callibrated in Fahrenheit and Celsius respectively, and when read by the meter, they produce ten millivolts per degree in their respective scales, so the meter can be directly read in temperatures, down to a tenth of a degree.这些都是callibrated是华氏度,摄氏度,分别按计价器显示金额看,他们millivolts生产10个每度在他们各自的秤上吗?这样表可直接读取,以至气温升高,以及刚过去的十分一的程度。 The digital thermometer needs these parts:数字温度计需要这些部分:
We carry all the parts for the digital thermometer (except the battery and optional parts) in our我们进行所有零件为数字温度计(除电池和选配件)catalog目录.
Shown above is a multimeter, set to read 0 to 2,000 millivolts (zero to two volts). 如上所示是万用表,读0到2000 millivolts(零到两个伏特)。Note that the dial switch is set to "2000 m".注意拨开关设置为" 2000米”。 It is currently reading 791 millivolts, which corresponds to 79.1 degrees Fahrenheit (since it is connected to the LM34 sensor).当前它是阅读791 millivolts,与外部华氏度(因为它连接到LM34传感器)。
Above, we have placed an LM35 sensor on top of an ice cube, and the pool of water melted from the ice is reading 8.9 degrees Celsius. 以上,我们将LM35传感器上的一块冰块里的水,从冰融化读8.9摄氏度。For this experiment we have simply connected alligator clips to two of the leads of the sensor, and wrapped the third lead with the red wire from the battery clip. 这个实验,我们只是连接两个鳄鱼剪辑过的传感器,包装,第三率先红色电线电池夹。No soldering, nothing fancy, and we have a digital thermometer in the time it takes to unwrap the meter and clip on the test leads.没有焊、没有花俏,我们数字温度计放进,所花???的时间,解开夹米,对测试引线。
For a more permanent thermometer, we solder three long wires (about 5 feet is nice) to the three leads of an LM34 Fahrenheit sensor. 为一种更持久的温度计、我们焊锡三声长导线(5英尺左右的很好)的三导LM34华氏传感器。Use three different colors, and note which ones are attached to which leads. 采用三种不同的颜色,注意哪些是导致上。We put a little electrical tape around the middle lead so it won't touch the other two, and then wrap the whole thing in electrical tape, or in this case, put it into a short length of heat shrinkable tubing, and warm it up so the tubing shrinks tightly around the whole assembly.我们把一个小电工胶带中间周围这么过它不会接触其他两个,然后把整个事件中,电工胶带或在此情况下,并投入长度较短的热收缩管材、和温暖所以油管缩小紧紧抱住全会众那里。 We made the wires long so that we can measure things inside boxes or behind doors. 我们的线长,所以里面,我们可以测量盒子或后面的门。Five feet makes it easy to place the sensor end in the refrigerator or freezer, and have the meter stay outside where it is easy to measure. 译:光脚身高五英尺就可以很容易地把传感器在冰箱里或冰箱结束,仪表在外面呆在那里很容易措施。This arrangement is great for incubators for eggs, and terrariums, or (with proper waterproofing) aquariums.这样的安排是伟大的为孵化器,小型饲养园,或者(用适当的防水)养鱼缸的器具。
At the other end of the long wires, we connect the battery clip and the resistor. 在另一端的长导线,将电池夹和电阻。Note that the wire colors help ensure that the right connections are made. 注意,电线颜色帮助确保正确的连接。In our case, the red wire from the battery clip is soldered to the brown and white striped wire, and the black wire from the battery clip is soldered to the brown wire. 在我们的例子中,红色电线电池夹焊接到棕色和白色相间的条纹电线和黑电线电池夹焊接“布朗电线。The brown wire is wrapped around one end of the resistor, and the blue wire is wrapped around the other end of the resistor. 棕色的线是裹住的电阻器的一端,蓝色线是裹在另一端的电阻。We can solder them later if we wish.我们可以焊接他们如果以后我们的愿望。
In the photo above you can see how the heat shrinkable tubing makes a nice neat temperature probe, with only the top of the sensor peeking out of the shrunken tube.上面图片中你可以看到热收缩管使漂亮整齐温度探测器,只有顶部的传感器摇曳的压缩管。 The alligator test leads are attached to the resistor, and the other ends are clipped onto the meter probes, as shown in the photo below.鳄鱼测试引线附在电阻器,和其他的目的都是夹到米探针,如图所示在照片下面。
How does it do that?它如何做呢?The internal workings and theory of the LM34 integrated circuit temperature sensor is内部运作,依据温度传感器LM34集成电路explained in minute detail by the manufacturer解释由制造商的细枝末节.
The circuit diagram is shown above. 线路图上面所示。Briefly, there are two transistors in the center of the drawing. 简而言之,有两个晶体管中心的这幅画。One has ten times the emitter area of the other. 有十倍的发射器其它区域。This means it has one tenth of the current density, since the same current is going through both transistors. 这就意味着有十分之一的电流密度,因为同一电流正在经历两个晶体管。This causes a voltage across the resistor R1 that is proportional to the absolute temperature, and is almost linear across the range we care about. 这引起的电压,电阻R1成正比,几乎绝对温度范围呈线性分布我们关心的人。The "almost" part is taken care of by a special circuit that straightens out the slightly curved graph of voltage versus temperature.“几乎”部分照顾到一种特别的电路,伸直微微弯曲的电压与图温度。 The amplifier at the top ensures that the voltage at the base of the left transistor (Q1) is proportional to absolute temperature (PTAT) by comparing the output of the two transistors.放大器上确保了电压在该基地的左晶体管(第一)是成正比的绝对温度(PTAT)的输出比较两个晶体管。 The amplifer at the right converts absolute temperature (measured in Kelvin) into either Fahrenheit or Celsius, depending on the part (LM34 or LM35). 在正确的使用的绝对温度转换(单位为开尔文)或进入华氏度或摄氏度,根据部分(LM34或LM35)。The little circle with the "i" in it is a constant current source circuit.小的环,“我”在这是一个恒流源电路。 The two resistors are calibrated in the factory to produce a highly accurate temperature sensor.这两个电阻是在工厂的校准产生一个高度精确的温度场的测量。 The integrated circuit has many transistors in it -- two in the middle, some in each amplifier, some in the constant current source, and some in the curvature compensation circuit. 集成电路有许多电晶体,它——两个在中间,一些在每个放大,一些恒流源,及一些曲率补偿电路。All of that is fit into the tiny package with three leads.所有这一切都适合进那包三导。 |
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