IR thermometer

Domestic ovens can be inexpensively and safely modified, however this almost eliminates these disadvantages and enables independent temperature measurement and reasonable temperature control. For temperature measurement an IR thermometer or, better, a fiber-optic thermometer [75-77] has been recommended. Such a batch microwave reactor made by modification of a domestic microwave oven is depicted in Fig. 13.1 and has been described elsewhere (Refs. [51, 75-77, 141-144] and references cited therein). 

For temperature measurements on the emerging extrudate, contacting-t)rpe measurements are not suitable because of damage to the extrudate surface. For non-contacting temperature measurements, infrared (IR) detectors can be used. The intensity of the radiation depends on the wavelength and the temperature of a body. Non-contact IR thermometers can be used to determine the temperature of the plastic after it leaves the die. IR sensors can also be used to measure the melt temperature inside the extruder or die see Section 4.3.3.2. 

The stream of radiation from the extrudate to the IR thermometer must be transmitted without absorption by the intervening atmosphere. This means that the IR thermometer must not operate in the spectral regions of atmospheric absorption bands. 

The correct value for the emittance of the extrudate must be known and correctly introduced into the IR thermometer calibration. 

Non-contact IR thermometers are used in a large number of extrusion operations blown film, cast film, biaxially oriented film, sheet, extrusion coating, etc. In some IR thermometers, an entire surface can be scanned and isotherms can be determined. With additional instrumentation, quantitative information on the temperature distribution can be obtained [5]. Portable infrared thermometers can be used to spot check the process, maintain equipment, and do general plant maintenance they are also very useful tools in troubleshooting. 

The non-contacting IR thermometer allows temperature measurement in spots that are difficult to reach with a contacting thermometer. Also, the IR thermometer allows measurement of polymer melt temperature without damaging the extruded product. It allows determination of the melt temperature variation across the melt stream coming out of a sheet die. Large melt temperature variations will generally create problems downstream. 

Another noninvasive tool to measure temperature is the infrared (IR) thermometer, which usually has an optical response time below 0.1 s. The measurement principle is based on determination of the thermal radiation Q oi a target body. The radiation is proportional to the temperature of the body according to the Stefan-Boltzmann law... 

Since the IR thermometer must adapt itself to the temperature of the surroundings, it may not measure the temperature accurately without enough time to adapt. The measurement results are also affected by the angle of optical axis to the surface as shown in Fig. 3. When the angle 9 is larger than 40°, an IR camera placed at position A gives temperature values higher than the real ones. 

US Infrared THERMOviewer Portable, battery-powered, uncooled BST 320 X 240 element IRFPA imager, 2-14 pm spectral range, 60-Hz frame rate. Boresighted IR thermometer provides spot measurement reference color display, aimed at low-cost PdM applications. 

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]. 

Temperature control Immersed gas balloon thermometer (max. 300 °C) outside IR remote sensor (max. 400 °C)... 

Temperature measurement is achieved by means of a remote IR sensor beneath the lower outer surface of the vessels. The operation limit of the IR sensor is 400 °C, but it is regulated by the software safety features to 280 °C as the operation limits of the materials used are around 300 °C. For additional control, temperature measurement in a reference vessel by means of an immersed gas-balloon thermometer is available. The operational limit of this temperature probe is 310 °C, making it suitable for reactions under extreme temperature and pressure conditions. 

An instrument for measuring temperatures, in the rubber industry the term is usually applied to an instrument for determining the surface temperature of mill and calender rolls, moulds, etc. The instrument is usually based on thermocouples or, where higher accuracy is required, platinum resistance thermometers. Infrared (IR) techniques are now used which have the advantage of non contact but require careful calibration for the emissivity of the surface. 

Most of the instruments, commonly used in an analytical laboratory, such as UV-Spectrophoto-meter, IR-Spectrophotometer, single—pan electric balance, pH-meter, turbidimeter and nephelometer, polarimeter, refractometer and the like must be calibrated duly, before use so as to eliminate any possible errors. In the same manner all apparatus, namely pipettes, burettes, volumetric flasks, thermometers, weights etc., must be calibrated duly, and the necessary corrections incorporated to the original measurements. 

Clayton RN, Epstein S (1958) The relationship between 0/ 0 ratios in coexisting quartz, carbonate and iron oxides from various geological deposits. J Geol 66 352-373 Clayton RN, Kieffer SW (1991) Oxygen isotope thermometer calibrations. In Taylor HP, O Neil JR, Kaplan IR (eds.) Stable isotope geochemistry A tribute to Sam Epstein. Geochem Soc Spec Publ 3 3-10... 

In 1800 Sir William Herschel found that a thermometer placed in the region beyond the red end of the solar spectrum (obtained by dispersing solar radiation with a prism) was heated even more than when placed in the visible portion Herschel had discovered infrared radiation. Around 1900 infrared (IR) absorption investigations of molecules began. 

A 39 g sample of crude 2,3,4-trimethoxy-l-allyloxybenzene in a round-bottomed flask with an immersion thermometer was heated with a soft flame. At 225 °C there was a light effervescence and at 240 °C an exothermic reaction set in that raised the temperature immediately to 265 °C. It was held there for 5 min, and then the reaction was allowed to cool to room temperature. GC and IR analysis showed the starting ether to be gone, and that the product was largely 2,3,4-trimethoxy-6-allylphenol. It weighed 34.4 g. 

Bimetal thermometer Turbine Bellow Magnetically coupled Infrared (IR) spectroscopy... 

Fig. 16 Temperature and power profiles for a Biginelli condensation (Scheme 2a) under sealed vessel/microwave irradiation conditions. Shown is the temperature measurement in one reference vessel via an internal gas balloon thermometer (T), the surface temperature monitoring of the eight individual vessels by IR thermography (IR 1-8), and the magnetron power (P, 0-1400 W). Reproduced with permission from [26]...

Figure 1. In-situ FTIR catalyst light-off temperature measurement system. 1. compressed air 2. mass flow controller 3. gas lecture bottle 4. MKS pressure gauge 5. exhaust 6. IR cell 7. IR window 8. catalyst sample 9. thermocouple 10. sample compartment of Nicolet FTIR Model 60SX 11. chart recorder 12. digital thermometer display.

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