Temperature measurement noise

A plot of the experimental data for a reactor (X, and can be used to determine a and b as well as check the validity of this functional form. For this approach to be effective, the temperature difference across the reactor needs to be large enough that temperature measurement noise does not signihcantly affect the results of the measured temperature. Once a and b are identified, the inlet temperature, can be adjusted to maintain a fixed reaction conversion, X. Periodically, composition measurements for the product leaving the reactor can be made and the results used to update the value of b in the previous equation, since a is less likely to change significantly compared with b. 

Many special-purpose electrical thermometers have been developed, either for use in practical temperature measurement, or as research devices for the study of temperature and temperature scales. Among the latter are thermometers which respond to thermal noise (Johnson noise) and thermometers based on the temperature dependence of the speed of sound. 

Model of ID dissipation spectrum from Pope [19] (line) and measured, noise-corrected spectrum of the square of the radial gradient of fluctuating temperature in a CH4/I-I2/N2 jet flame (Re = 15,200) (symbols). Each spectrum is normalized by its maximum value. The arrow indicates the 2% level, which corresponds to the normalized wavenumber k = 1 according to the model spectrum. (From Barlow, R.S., Proc. Combust. Inst., 31, 49,2007. With permission.)... 

Cases 4 and 5 deserve some special consideration. They were performed under the same conditions in terms of noise and initial parameter value, but in case 5 the covariances (weights) of the temperature measurements were increased with respect to those in the remaining measurements. For case 4 it was noticed that, although a normal random distribution of the errors was considered in generating the measurements, some systematic errors occur, especially in measurement numbers 6, 8,... 

This was also done in order to attribute the temperature oscillations only to the interconnection. Time series were filtered (see solid lines in Figures 3 and 4) by low-pass filter in order to eliminate noise effects in temperature measurements (in Figures 3 and 4, the dotted line and the solid line correspond, respectively, to the temperature measurements and the filtered temperature). 

The resulting principal values of the 13C chemical shift tensors of the C60 carbons are 8n = 228 ppm, 822 = 178 ppm, and 833 = -3 ppm. Tycko et al reportet the experimental values 8n = 213 ppm, S22 = 182 ppm, and 833 = 33 ppm obtained from low temperature measurements of a powder pattern spectrum (18). However, the spectra have a low signal to noise ratio and a wide slope so that a larger error for the experimental value can be assumed. The chemical shift anisotropy of 217 ppm corresponds quite well with the spectral range of about 200 ppm reported by Kerkoud et al for low temperature single crystal measurements (19). 

Because the spatial area with higher temperature on the catalyst surface of one of the samples of the library is very small the detection of catalytic activities through temperature measurement cannot be carried out by direct temperature measurements but only by non-contact methods such as pyrometry or IRT. The IR video camera used here measures the emission at every point of the library in parallel. The detector consists of a 256x256 pixel array of Pt-silicide-IR-sensors. Each pixel delivers a voltage-signal that depends on the infrared radiation and the sensitivity of that pixel (fixed pattern noise). 

The performance of the robust estimators has been tested on the same CSTR used by Liebman et al (1992) where the four variables in the system were assumed to be measured. The two input variables are the feed concentration and temperature while the two state variables are the output concentration and temperature. Measurements for both state and input variables were simulated at time steps of 1 (scaled time value corresponding to 2.5 s) adding Gaussian noise with a standard deviation of 5% of the reference values (see Liebman et al, 1992) to the true values obtained from the numerical integration of the reactor dynamic model. Same outliers and a bias were added to the simulated measurements. The simulation was initialized at a scaled steady state operation point (feed concentration = 6.5, feed temperature = 3.5, output concentration = 0.1531 and output temperature = 4.6091). At time step 30 the feed concentration was stepped to 7.5. 

In another study [35], the electrochemical emission spectroscopy (electrochemical noise) was implemented at temperatures up to 390 °C. It is well known that the electrochemical systems demonstrate apparently random fluctuations in current and potential around their open-circuit values, and these current and potential noise signals contain valuable electrochemical kinetics information. The value of this technique lies in its simplicity and, therefore, it can be considered for high-temperature implementation. The approach requires no reference electrode but instead employs two identical electrodes of the metal or alloy under study. Also, in the same study electrochemical noise sensors have been shown in Ref. 35 to measure electrochemical kinetics and corrosion rates in subcritical and supercritical hydrothermal systems. Moreover, the instrument shown in Fig. 5 has been tested in flowing aqueous solutions at temperatures ranging from 150 to 390 °C and pressure of 25 M Pa. It turns out that the rate of the electrochemical reaction, in principle, can be estimated in hydrothermal systems by simultaneously measuring the coupled electrochemical noise potential and current. Although the electrochemical noise analysis has yet to be rendered quantitative, in the sense that a determination relationship between the experimentally measured noise and the rate of the electrochemical reaction has not been finally established, the results obtained thus far [35] demonstrate that this method is an effective tool for... 

Refractive index detectors continuously monitor the difference in bulk RI of the mobile phase and that of a reference mobile phase containing no solute. As such, RI is a bulk property detector. Unlike UV detectors, RI detectors are highly sensitive to temperature fluctuations and somewhat sensitive to flow rate fluctuations. Temperature should be maintained within 0.001°C for high-sensitivity measurements. Noise equivalent concentration for RI is IQ- g/ml. ... 

Since temperature measurements are required over such a wide range and diversity of situations, a large number of different types of thermometers with varying levels of accuracy and convenience have been developed over the years. Those most frequently used are based on the expansion of a gas, liquid or solid on changes in electrical resistance on the thermoelectric effect on changes in the thermal radiation of a system on changes in the thermal (Johnson) noise of electrical resistors on changes... 

It was found that the control loop could successfully operate at a rate of 500 Hz with all 24 microreactor heaters being under closed-loop PID control. At faster rates, the processor had insufficient time to complete the TCP/IP communications with the HMI, which resulted in data loss. Somewhat conservative loop parameters were used because of the noise in the temperature measurement signal, but temperature control was quite stable imder a wide variety of both reactive and non-reactive conditions. The dynamics of the closed loop control algorithm were not explored since the data logging rate (4 Hz) was not fast enough to perform these types of evaluations. This would be possible with program modihcations, but this issue was not a project objective. It could be considered as a topic for future investigation. 

T. V. Blalock and R. L. Shepard, A Decade of Progress in High-Temperature Johnson Noise Thermometry, in Temperature Its Measurement and Control in Science and Industry, vol. 5, pt. 2, American Institute of Physics, New York, 1982. 

Barton, S., and Garneau, J. M. "Effect of Pump-Laser Linewidth on Noise in Single-Pulse Coherent Anti-Stokes Raman Spectroscopy Temperature Measurements." Optics Letters 12, no. 7 (1987) 486. 

In this section, Bayesian analysis is performed to identify the uncertain coefficients of the quadratic function. The effective temperature T is assumed to be different from the measured values since there is measurement noise in the data acquisition process and the temperature in different parts of the building could also be non-uniform. The difference is assumed Gaussian with zero mean and variance a. In this study, this standard deviation is taken to be aj = 0.5°C since the difference between the indoor and outdoor temperature measurement was around 1 °C and the average value was used as the measured temperature T for the wth day. On the other hand, the squared fundamental frequency is identified by the Bayesian spectral density approach to be presented in Chapter 3. Therefore, the uncertain parameters include the coefficients of thequadratic function and the effective temperatures 0 = [l>o, b, b2, T, Ti,7 ], where iV is the number of data points. The data include the measurements of the temperature and the identified squared fundamental frequencies X> = [li,. .., j, 2> >... 

DMC uses a direct, least-squares computational procedure to find the optimum values of future changes in the manipulated variables to match future output responses such that some performance index is minimized [8]. Panda applied DMC to control the fluid-bed dryer as mentioned earlier and proved that DMC gives better control in the presence of measurement noise [19]. The response in the exit-air temperature does not show much oscillation and settles quickly. 

The resolvable spatial resolution of temperature measurements in liquids mainly depends on the concentration of the TLCs in the suspension, the size of the averaging area (interrogation area) and the size of the TLC particles. To decrease the size of the averaging area, a better hue response of the temperature of the TLCs is needed. Since the concentration of the encapsulated TLCs in the suspension is restricted by the signal-to-noise ratio, only a smaller diameter of the particles can improve the resolvable spatial resolution. 

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