Temperature measurement corrections

Temperature measurements (corrected for radiation) were made with silica-coated Pt-Pt/10% Rh thermocouples, about 4 mils in diameter. The temperature and species concentration profile as a function of distance through the flame provided the basic data for the kinetic analyses. 

Winding temperature measurement at site 10/241 10.6.1 Temperature correction 10/241... 

The simplest calibration procedure for a gas flow-measuring device is to connect it in series with a reference meter and allow the same flow to pass th tough both instruments. This requires a reference instrument of better metrological quality than the calibrated instrument. One fact to consider when applying this method is that the mass flow rate in the system containing both instruments is constant (assuming no leakage), but the volume flow rate is not. The volume flow rate depends on the fluid density and the density depends on the pressure and the temperature. The correct way to calibrate is to compare either the measured mass... 

Intelligent transmitters have two major components (1) a sensor module which comprises the process connections and sensor assembly, and (2) a two-compartment electronics housing with a terminal block and an electronics module that contains signal conditioning circuits and a microprocessor. Figure 6.9 illustrates how the primary output signal is compensated for errors caused in pressure-sensor temperature. An internal sensor measures the temperature of the pressure sensor. This measurement is fed into the microprocessor where the primary measurement signal is appropriately corrected. This temperature measurement is also transmitted to receivers over the communications network. 

A particularly difficult problem in microwave processing is the correct measurement of the reaction temperature during the irradiation phase. Classical temperature sensors (thermometers, thermocouples) will fail since they will couple with the electromagnetic field. Temperature measurement can be achieved either by means of an immersed temperature probe (fiber-optic or gas-balloon thermometer) or on the outer surface of the reaction vessels by means of a remote IR sensor. Due to the volumetric character of microwave heating, the surface temperature of the reaction vessel will not always reflect the actual temperature inside the vessel [7]. 

Milton et al. [1.136] used this methods and refer to it as manometric temperature measurement. They used times of pressure rises of up to 30 s. During this time, the ice temperature will increase, mainly due to continued heat flow. Therefore, an equation has been developed to transform the experimental pressure data, including three other corrections, into the true vapor pressure of the ice. If the valve is closed for only a very short time, < 3 s, and the pressure is measured and documented 60 to 100 times/s, these data can be recorded as shown in Fig. 1.78.1. The automatic pressure rise measurements (1) can then be plotted... 

It is possible to check the calibration of a pipet, flask, or buret. The process involves weighing with a calibrated analytical balance. The volume of water (temperature noted) delivered or contained by the glassware is weighed. Then the analyst converts this weight to volume (using the density of water at the temperature noted), corrects the result to 20°C (the usual temperature of the factory calibration), and compares it to the factory calibration. If the difference is not tolerable, the piece of glassware is either not used for accurate work or a correction factor is applied. It should be pointed out that the thermometers used must be properly calibrated and that the timer used to measure the delivery time for the burets and pipets must also be calibrated. 

In Ramsay s experiments the forms of apparatus used were capable of sustaining pressures up to 100 atmospheres. The wide and narrow tubes were concentric the wide tube was therefore annular in shape, and the allowance for the capillary rise in it becomes difficult to calculate. Ramsay did not make a sufficient allowance for the rise in the annular tube and in consequence all his values, and those of later workers who have adopted his figures for purposes of calibration for surface tensions are too low. Sugden has used an approximate method of correcting for the rise in the annulus, in which he considers a capillary tube of circular bore which gives an identical rise at a particular temperature and for a particular liquid, and assumes that the rise in the two tubes will be the same for all other temperatures and liquids. By this means he has, with the help of later measurements, corrected all Ramsay s values for which sufficient data are given in the original papers. 

Figure 6 7. Value and 95% confidence interval on the volume delivered by a nominal 10.0000-mL pipette, with different corrections applied. Cal. volume calibrated by 10 fill-and-weigh experiments. Temp volume corrected for temperature measured in the laboratory.

Flow of Suspended Particles. Small particles suspended in the combustible stream have been used for the study of Bunsen flames. Andersen and Fein 2P) use strobo-scopically illuminated particle tracks for the determination of normal burning velocities and flame temperatures. Flame studies using similar techniques are reported by Fristrom, Avery, Prescott, and Mattuck (3P). Wolfhard and Parker 10P) have made temperature measurements of flames containing incandescent particles. The acceleration of flow through a flame front causes particles greater than about 2 microns to lag. Thus, the particles may not follow the flow streamlines. Gilbert, Davis, and Altman (4P) discuss the corrections which must be applied to obtain accurate results. 

Accuracy of thermocouples should be 0.5°C. Temperature accuracy is especially important in steam sterilization validation because an error of just 0.1 °C in temperature measured by a faulty thermocouple will produce a 2.3% error in the calculated F0 value. Thermocouple accuracy is determined using National Bureau of Standards (NBS) traceable constant temperature calibration instruments such as those shown in Figure 6. Thermocouples should be calibrated before and after a validation experiment at two temperatures 0°C and 125°C. The newer temperature-recording devices are capable of automatically correcting temperature or slight errors in the thermocouple calibration. Any thermocouple that senses a temperature of more than 0.5°C away from the calibration temperature bath should be discarded. Stricter limits (i.e., <0.5°C) may be imposed according to the user s experience and expectations. Temperature recorders should be capable of printing temperature data in 0.1 °C increments. 

This example provides several valuable lessons, some of which are the same as observed in previous examples. First, the experimental conditions and compositions need to be the same for calibration and routine operation. In this example, the initial on-line measurements were biased relative to the reference values. This was traced to the temperature differences between the on-line samples (100-200°C) and the room temperature samples used to build the calibration models. Raman band intensity is a known function of temperature, but affects high- and low-frequency bands unequally. A separate temperature measurement enabled the results to be corrected. 

The conditions for obtaining the correct heating should be checked by means of a fine wire thermocouple inserted through a pierced lid having its unprotected junction in contact with the center of the base of the empty crucible. The end of the couple should be formed into a flattened loop so that the junction and a portion of each wire rests on the bottom of the crucible during a temperature measurement. The couple should be made of wires not heavier than 34-gauge platinum or 26-gauge base metal. 

---