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yinglv金虫 (正式写手)
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[求助]
求关于热电偶的几段话的翻译【英译汉】
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7.3 Reference Junction Temperatures—A controlled temperature medium shall be provided in which the temperature of the thermocouple reference junctions is maintained constant during a measurement cycle at a known or measured value. A commonly used reference temperature is 0 °C (32 °F), usually realized through use of the ice point, but other temperatures may be used if desired. An acceptable method for utilizing the ice point as a reference junction is given in Practice E 563. Reports of data taken with reference temperatures other than the ice point should be corrected to reflect the results that would have been obtained if the reference junction had been at the ice point. As an alternative, calibration data taken with a reference junction temperature other than the ice point may be reported without correction, but in such cases the calibration report must clearly state the actual reference junction temperature. The reference junction temperature shall be known or measured with uncertainty less than that expected from the thermocouple calibration, to minimize this temperature variation as a source of error. 7.3.1 Isothermal and Electronic Reference Junction Compensation—For the rapid calibration of large numbers of thermocouples, the reference junctions can be made at an isothermal multiterminal strip. This avoids the thermal loading of the ice bath resulting from the large number of thermocouple and copper connecting wires. The temperature and isothermal condition of the strip shall be established and monitored by the use of a separate, reference temperature sensor. The spatial temperature variation across the terminations on the isothermal unit shall be mapped and accounted for. If desired, the thermocouple emf values obtained with use of an isothermal terminal strip may be compensated such that the compensated emf is equivalent to the thermocouple emf created by a thermocouple with reference junctions at 0 °C (32 °F). An electronic reference junction compensator accomplishes this task by accurately monitoring the temperature of the reference junctions and adding to the thermocouple emf an additional emf such that the sum is equivalent to the thermocouple emf produced with reference junctions at 0 °C. The addition of emf to the thermocouple emf may be accomplished through software methods, as well as through addition of an actual emf. To minimize the uncertainty of an electronic reference junction emf as a source of error, the temperature equivalent of the emf produced by the electronic reference junction shall be known and measured with uncertainty less than that expected from the thermocouple calibration. Whatever reference junction technique is used, its uncertainty must be accounted for in the uncertainty of the thermocouple calibration being performed. 7.3.2 Extension of Thermoelements to Reference Temperature—Whenever possible, the thermoelements under test shall be continuous, extending from the measuring point through the temperature gradient, to the reference junction without any intermediate connections. In cases where this is not possible, several options exist: 7.3.2.1 Matched Thermoelements—Additional lengths of thermoelement materials from the same wire lots as those being calibrated may be used to extend the device under test to the reference bath. In such circumstances, no additional corrections are required. 7.3.2.2 Thermoelements of the Same Type with Known Thermoelectric Response, but from a Different Lot—Thermoelements being calibrated may be extended using thermoelement materials of the same type as the thermocouple under test. Such materials may be of thermocouple or extension grade, but shall have a known emf versus temperature relationship over the temperature interval to which they will be subjected, and corrections for the deviations of the extension material relative to the material under test over that interval shall be made. In general, it will be necessary to calibrate the test wire in the temperature range spanned by the extension wire and to measure the temperature of the junctions between the different materials in order to make this correction. No correction is necessary if both ends of the extension material are at temperatures within 1 °C (1.8 °F). It is also acceptable to not apply a correction if the uncertainty budget for the calibration includes an appropriate allowance for temperature variations of the junction between the thermocouple and the extension material, and the calibration report specifies the range of transition junction temperatures for which the calibration is valid. This allowance may be experimentally determined by maintaining the measuring junction of the thermocouple at a fixed temperature, such as 0 °C, and varying the temperature of the transition junction over a specified range. 7.3.2.3 Thermocouple Connectors—In all cases where there are junctions between the thermocouple under test and thermocouple lead wires, the temperature variations across the junctions shall be minimized. Thermocouple connectors as described in Specifications E 1684 and E 1129 will introduce no more than 1.1 °C (2 °F) error for a 40 °C (70 °F) temperature difference across the connector. This error will be proportionately reduced for smaller temperature differences. 7.3.2.4 Circumstances with Small Temperature Differences—In special cases where the temperature differences from end-to-end along the length of the wires used to extend a thermocouple for calibration purposes are very small (less than 62 °C), thermocouple or extension grade wires of matching thermocouple type may be used in calibration circuits without correction. 7.4 Emf-Measuring Instruments—The choice of a specific instrument to use for measuring the thermocouple emf will depend on the accuracy required of the calibration being performed. Generally the thermocouple emf will be measured using a digital voltmeter. For the highest level of accuracy, voltmeters shall have a maximum uncertainty no greater than 10-4 times the emf reading and shall have input impedances larger than the thermocouple loop resistance by at least a factor of 104. Reference junction compensation is required for thermocouple measurement with voltmeters. In order to avoid forming unintended reference junctions at voltmeter terminals whose temperature may be poorly controlled, thermocouples must not be connected directly to the input terminals of voltmeters without the use of appropriate electronic reference junction compensation and connection of the voltmeter to the compensator with untinned copper wires. 7.5 Connecting Wire Assembly—Connecting wires from the reference junction to the voltmeter shall be insulated copper and shall be configured as twisted pairs for wire lengths greater than 0.3 m (1 ft.), to reduce electromagnetic noise pickup. If the environment contains substantial electromagnetic noise, it may also be useful to run the wires in a grounded electrical shield or braided cable. Copper connections should be clean and free from oxides. 7.5.1 Scanner systems may be used to switch between the reference thermometer and the different thermocouples being calibrated. Such switches shall be of rugged construction and designed so that both connecting wires are switched when switching from one thermocouple to the next, leaving thermocouples not in use electrically isolated. All of the scanner switches shall be constructed of the same material and shall be free of extraneous emf production (see Appendix X3). Precautions should be taken to protect the switches from temperature fluctuations due to convection, conduction, or radiation. Scanning performance shall be evaluated to ensure adequate settling time before measurement. 7.5.2 It is preferable to use wire-to-wire connections in calibration circuits, but if terminal blocks are used for convenience, they shall be protected against the development of temperature gradients across the blocks. 7.6 Thermocouple Insulation and Protection Tubes—In the case where bare wire thermocouples are tested, two-hole insulation tubing may be used to support and electrically insulate the immersed portion of the two bare thermoelements. Use only insulation material that will not contaminate the thermocouple (for example, clean, high-purity insulators such as 99.8 % aluminum oxide) and that will provide the necessary electrical insulation at the highest temperature of the calibration. To prevent contamination of thermocouples by residues left by previously tested thermocouples, each insulator shall only be used with thermocouples of one type and the positive and negative thermoelements shall always be inserted in the same bore. The only exceptions allowed are: type R and type S thermocouples may be calibrated in the same insulators, and the thermoelements of type B thermocouples may be mounted in either bore. To avoid unnecessary mass and to minimize axial heat conduction in the region of the measuring junction, the tubing should be relatively thin walled. Bore diameters should provide a loose fit for the thermocouple wires. During the test, the thermocouples may be inserted in a protection tube that is resistant to thermal shock, and noncontaminating to the thermocouple materials. 7.6.1 Sheathed thermocouples may be tested without further protection or support in liquid or dry fluidized baths, provided that the bath medium is compatible with the sheath material. Thermocouples insulated with fibrous insulation must not be immersed directly into any bath liquid. Care must be taken to keep thermal conduction losses within the limits of experimental error typically by immersing the thermocouple into the bath until no further indication in temperature change is noted. 注：emf表示电动势 |
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7．6热电偶绝缘和保护管—有裸线的热电偶在进行测试的时候，可以通过将两个裸露的热电原件插入双孔绝缘管使插入双孔绝缘管的部分进行绝缘。仅使用绝缘材料不会污染热电偶（例如干净的、高纯度的绝缘体比如99.8%氧化铝）并且热电偶在校正的时候绝缘材料能够提供必要的电绝缘。 为了避免先前测试热电偶时留下的残渣对热电偶的污染，每一个绝缘管将仅被用于一种类型的热电偶并且热电偶的正极负极热点元件将始终插在同一个孔内。仅有的例外是：R和S型的热电偶可以在统一绝缘管内校正，并且B型热电偶的热点元件能够安装在绝缘管的任一孔。为避免不必要的物质和使测量接合点区域轴向热传导的最小化，绝缘管的管壁相应地要薄。孔直径要足够大小以便热电偶的电线能够轻松安装。在测试过程中，热电偶可插入在一个能够抵抗热量冲击并且对热电偶材料无污染的保护管中。 拥有保护层的热电偶可以在没有更深层保护或者在湿态或干态流化床辅助的情况下进行测试，测试的前提是假设流化床的媒介与热电偶保护层材料是相兼容的。 经过含纤维性物质进行绝缘的热电偶一定不要直接浸入任何流化床流体。一定要留意维持热传导的损失在实验误差的范围内，这个可以典型地通过将热电偶浸入流化床直到检测不到温度变化的更深层信息。 |
6楼2008-11-12 22:18:12
2楼2008-11-04 19:22:16
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3楼2008-11-06 11:51:19
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7.3参考结温度，控制温度中期应提供在该温度范围热电偶路口经常保持在测量周期在已知或测量值。一个常用的参考温度为0 ℃ （ 32 ° F ）的，通常是通过使用冰点，但其他的温度可用于如果需要的话。一个可接受的方法，利用冰点作为参考交界处是在实践中é 563 。报告的数据与参考温度以外的冰一点应该予以纠正，以反映成果，已获得的参考，如果交界处已在冰点。作为一种替代办法，采取校正数据与结温范围以外的其他点冰可能会报告未经修正，但在这种情况下，校准报告必须明确指出的实际结温范围。 交界处的温度范围应已知或测量的不确定性低于预期热电偶校准，尽量减少这种温度变化的一个来源的错误。 7.3.1恒温和电子参考结 补偿的快速校准大量的热电偶，路口的提法，可在温多端地带。这避免了热负荷的冰浴造成大量的热电偶和铜连接线。温度和温条件的地带应设立和监督使用一个单独的，参考温度传感器。空间温度变化在终止对温单位应制定和交代。如果想要的话，热电偶电动势值获得与使用等温端带可能得到补偿，使补偿电动势等于热电偶电动势所造成的热提到路口，在0 ℃ （ 32 ° F ）的。电子参考交界补偿完成这一任务的准确监测的温度范围，增加路口的热电偶电动势额外的电动势这样的总和相当于生产热电偶电动势参考路口，在0摄氏度新增的电动势的热电偶电动势可以通过软件的方法，以及通过增加一个实际电动势。为了尽量减少不确定性的电子参考交界电动势作为一个来源的错误，温度相当于电动势所产生的电子参考交界处应称为和测量的不确定性低于预期热电偶校准。无论交界技术参考使用，它的不确定性必须占的不确定性，热电偶校准履行。 7.3.2推广Thermoelements参考 温度在可能情况下，根据测试thermoelements应不断扩大的测点的温度梯度，以交界的提法没有任何中间连接。在此情况下，是不可能的，存在着几种选择： 7.3.2.1匹配Thermoelements -附加长度thermoelement材料来自同一线手那些被校准可用于延长设备的测试参考洗澡。在这种情况下，任何额外的更正是必需的。 7.3.2.2 Thermoelements同一类型与已知 热电响应，但是从一个不同的地段， Thermoelements标定可以延长使用thermoelement材料同一类型的热电偶进行测试。这种材料可热电偶或延期级，但须有一个已知的电动势随温度的关系的温度间隔，他们将受到和修正偏差的相对延长材料的物质进行测试超过这一区间 应。一般来说，将有必要校准测试线中的温度范围内跨区延长线和衡量的温度之间的路口 不同的材料，以便使这一更正。无修正是必要的，如果两端延长材料在温度在1摄氏度（华氏1.8度） 。这也是可以接受的不适用纠正的不确定性，如果预算的校准包括一个适当的津贴温度变化的交界处之间的热电偶和延长材料和校准报告指定范围内的过渡交界处的温度而校准有效。这项津贴可确定的实验测量维护交界处的热电偶在一个固定的温度，如0 ℃ ，和不同的温度比交汇处过渡指定的范围内。 7.3.2.3热电偶连接器，在所有情况下，有路口之间的热电偶进行测试和热电偶导致电线，在温度变化的整个路口，应减少到最低限度。热电偶连接器中所描述规格é 1684和E 1129年将推出不超过1.1 ℃（2 ° F）的误差为40 ℃（70 °F）的温度差在连接器。这个错误将减少比例较小的温差。 7.3.2.4低温情况下 差异，在某些特殊情况下的温度差异端到端沿长度的电线用来延长热电偶校准的目的是非常小（小于62 ℃ ） ，热电偶或延长线级的匹配热电偶类型可用于校准电路没有更正。 7.4电磁场测量仪器，选择一个特定的工具用于测量热电偶电动势将取决于所需的精度的校准履行。一般来说，热电偶电动势将成为衡量使用数字电压表。对于最高级别的准确性， 电压表须有一个最大的不确定性不大于10-4倍电动势读，并须有输入阻抗大于热电偶回路电阻至少一个因素104 。参考交界补偿所需的热电偶测量电压表。为了避免 形成意想不到的参考路口，在电表终端的温度可控制不良，热电偶不能直接连接到输入终端电压表没有使用适当的电子参考交界补偿和连接的电表的补偿与untinned铜线。 7.5连接线装配连接线参考交界处的电表应绝缘铜，并应配置为双绞线的导线长度大于0.3米（ 1英尺） ，以减少电磁噪声小。如果环境包含大量的电磁噪声，也可能是有用的运行线路在电力系统接地或编织线。铜连接应清洁，无氧化物。 7.5.1扫描系统可用于交换机之间的参考温度计和不同的热电偶标定。这种交换机应坚固耐用的建筑和设计的，因此这两个连接线切换开关时，从一个热电偶下，使热电偶在不使用电气绝缘。所有的扫描仪开关须以同样的材料，并应免费不相干的电动势生产（见附录的X3 ） 。预防应采取以保护交换机的温度波动由于对流，传导或辐射。扫描性能应进行评估，以确保有足够的时间才能解决的测量。 7.5.2最好使用线，以线连接的校准电路，但如果接线端子用于方便的时候，他们应受到保护，免遭发展的温度梯度整个区块。 7.6绝缘热电偶和保护管，在的情况下，电线裸露热电偶进行测试，两个洞绝缘管可以用来支持和电气的浸泡隔绝部分的两个裸thermoelements 。 仅使用绝缘材料，不会污染热电偶（例如，清洁，高纯度的绝缘体，如99.8 ％氧化铝） ，并提供必要的电气绝缘的最高温度校准。 为了防止污染的热电偶的残留以前遗留下来的测试热电偶，每个绝缘子应只用热电偶的一种类型，并积极和消极thermoelements应始终插入在同一口径。唯一的例外允许有： R型和S型热电偶校准可在同一绝缘子，并thermoelements B型热电偶可安装在任何承担。为了避免不必要的质量，并尽量减少轴向热传导区域的交界处测量，油管应相对薄壁。孔的直径应该提供一个宽松适合热电偶电线。在测试中，热电偶可插入保护管的抗热冲击，并noncontaminating的热电偶材料。 鞘热电偶7.6.1可测试时没有进一步的保护或支持在液体或干流化床洗澡，只要洗澡中型符合护套材料。 热电偶与纤维隔热保温绝不能沉浸直接进入任何浴液体。必须注意保持热传导损失的范围内，实验误差通常由热电偶浸泡到浴缸，直到没有进一步说明在温度变化的。 [ Last edited by wrenxiu on 2008-11-9 at 22:00 ] |
4楼2008-11-09 21:58:38
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