Temperature measurements, accuracy

Several effects can play a role in the temperature measurement accuracy. Due to the small channel length, the temperature difference between the channel outlet and inlet can be as small as the sensor sensitivity. Thermocouples can have a size comparable to the channel dimensions and where is measured the temperature is questionable. Moreover, the heat flow rate through the thermocouple itself can be not negligible. The importance of these effects must be appreciated. 

An estimate of the temperature measurement accuracy of the instrument is provided by tests performed in Air Liquide s 500 kW oxy/air-fuel pilot furnace. 

As described in Section 14.2.2, TDL-based measurement of temperature along a beam path is possible in theory by using the ratio of two H2O absorption features. The ZoloBOSS, however, measures temperature using six H2O features. This large number of features is used to improve temperature measurement accuracy (Sappey and Zimmerman 2008). 

ZoloBOSS temperature and species concentration measurement capabilities. The firm has also performed full-scale temperature measurement accuracy testing in power plant conditions (Sappey and Zimmerman 2008). These tests are described next. 

The unique measurement capabilities, good temperature measurement accuracy, and robust mechanical design of the ZoloBOSS instrument are notable, and these attributes appear to meet industrial requirements as evidenced by a number of existing industrial installations. Future developments and applications of the ZoloBOSS will be of interest to those in the combustion community who require insight into their combustion processes. 

Cross section test points (B-) were measured by using WRN-type K thermocouple with temperature measuring range -50-400 °C, and temperature measurement accuracy 0.75% 2.5 °C. TES-1310 digital temperature meter was used as a monitor with resolution 0.1 °C, temperature measuring range -50 °C 199.9 C, and temperature measurement accuracy (0.3%-hl °C). 

The bq34z653 device from Texas Instruments includes all of the required functions plus an LCD display and external heater mechanism to ensure reliable operation in extreme conditions. (The heater can be used to heat the LCD display for low-temperature operation). The device also contains two thermistor temperature inputs for additional temperature-measuring accuracy. 

As fully distributed BOTDA sensors, the optical fiber has functions of sensing and data transmission. Using the newly developed PPP-BOTDA technology, the strain and temperature measurement accuracy can be increased to be 7 ie, and 0.3 °C, respectively, with a spatial resolution of 2 cm. Therefore, a high-accuracy slope strain sensing network can easily be constructed. The installation technique of this technology is relatively simple. The sensing fiber can be embedded in the slope mass or installed... 

The accuracy and reproducibility of hard tissue analysis results can be significantly affected by a number of experimental parameters such as sample shape, size and mass, analysis atmosphere or sample thermal and mechanical history. Sample representativeness, adequacy of sample mass to the desired test accuracy, and avoidance of inducing changes or contamination are key factors that should be monitored in order to obtain reproducible results on kindred specimens. Achieving this goal can be difficult when the experimental and instrumental parameters are not identical, since the thermal analysis methods are sensitive to heat transfer and temperature measurement accuracy [7,21]. 

In the use of temperature measurement for control of the separation in a distillation column, repeatability is crucial but accuracy is not. Composition control for the overhead product would be based on a measurement of the temperature on one of the trays in the rectifying section. A target would be provided for this temperature. However, at periodic intervals, a sample of the overhead product is analyzed in the laboratory and the information provided to the process operator. Should this analysis be outside acceptable limits, the operator would adjust the set point for the temperature. This procedure effectively compensates for an inaccurate temperature measurement however, the success of this approach requires good repeatability from the temperature measurement. 

As normally used in the process industries, the sensitivity and percentage of span accuracy of these thermometers are generally the equal of those of other temperature-measuring instruments. Sensitivity and absolute accuracy are not the equal of those of short-span electrical instruments used in connection with resistance-thermometer bulbs. Also, the maximum temperature is somewhat limited. 

The commercial units have a very low thermal capacity and very high response speeds. Some are available with several independent channels and a common cold junction. Each channel is scanned in turn by the instrument, and the readings either displayed or stored for future recovery. Accuracies of better than 0.2 per cent are possible. Thermocouples are available to cover a very wide range of temperatures, their cost is low and they have a small mass, so minimizing the intrusive effect on the surface at the point where the temperature is being measured. The output characteristics (output voltage versus temperature) are reasonably linear but the measurement accuracy is not particularly high. 

Rodebush has also implied that the accuracy with which very low temperatures can be measured is restricted by the uncertainty principle and by the nature of the substance under investigation. However, the accuracy of a temperature measurement is not limited in a serious way by the uncertainty principle for energy, inasmuch as the relation between the uncertainty in temperature and the length of time involved in the measurement depends on the size of the thermometer, and the uncertainty in temperature can be made arbitrarily small by sufficiently increasing the size of the thermometer we assume as the temperature of the substance the temperature of the surrounding thermostat with which it is in either stable or metastable equilibrium, provided that thermal equilibrium effective for the time of the investigation is reached. 

There s another reason why the computed solution average temperature had decreasing accuracies in Tests 1, 2 and 3 respectively. The reason is that we started with increasingly viscous solutions, which caused the response time of the temperature measurement to increase rapidly. This response time becomes even more significant because as the solution viscosity increases there are significant rises in the reaction rates and temperatures. 

Monton and Llopis (1994) presented VLE data at 6.66 and 26.66 kPa for binary systems of ethylbenzene with m-xylene and o-xylene. The accuracy of the temperature measurement was 0.1 K and that of the pressure was 0.01 kPa. The standard deviations of the measured mole fractions were less than 0.001. The data at 26.66 for the ethylbenzene (1) - o-Xylene (2) are given in Table 15.8 and the objective is to estimate the NRTL and UNIQUAC parameters based on these data. 

Errors in density result from errors in temperature measurement or control calibration of instruments transfer, handling and weighing of samples and impurities in the samples. At temperatures well below the critical temperature and near room temperature, standard techniques easily achieve accuracies of +0.05%. For the compounds in this compilation, that level corresponds to about +0.4 kg m"3. Under these conditions, errors in temperature are not very significant. This level of accuracy only requires... 

The contact resistance may change when the thermometer is moved from a position to another. Hence the accuracy of resistance temperature measurements below about 25 mK... 

The temperature measurement during secondary drying with Th or RTD is possible, as shown in Fig. 1.63, with an accuracy of approx. 2 °C. 

The comparison of simulation and measurement data of an uncoated membrane is shown in Fig. 4.7. The temperature curves, T to T4, were measured with the on-membrane temperature sensors. The graphs of the simulated temperatures are denoted Si to S4. The temperature discrepancy between simulation and experiment was less than 5% for all sensors. The general shape of the temperature distribution was correctly modeled within measurement accuracy. It has to be noted that no additional fitting parameters were used for these simulations. 

In some manufacturing process analysis applications the analyte requires sample preparation (dilution, derivatization, etc.) to afford a suitable analytical method. Derivatization, emission enhancement, and other extrinsic fluorescent approaches described previously are examples of such methods. On-line methods, in particular those requiring chemical reaction, are often reserved for unique cases where other PAT techniques (e.g., UV-vis, NIR, etc.) are insufficient (e.g., very low concentrations) and real-time process control is imperative. That is, there are several complexities to address with these types of on-line solutions to realize a robust process analysis method such as post reaction cleanup, filtering of reaction byproducts, etc. Nevertheless, real-time sample preparation is achieved via an on-line sample conditioning system. These systems can also address harsh process stream conditions (flow, pressure, temperature, etc.) that are either not appropriate for the desired measurement accuracy or precision or the mechanical limitations of the inline insertion probe or flow cell. This section summarizes some of the common LIF monitoring applications across various sectors. 

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