Calibration of the Temperature Sensors

The discrete microhotplates were packaged and bonded in a DIL-28 package for temperature sensor cahbration. A Pt-lOO-temperature sensor was attached to the chip package in close vicinity to the sensors. The chips were then caHbrated in an oven at temperatures up to 325 °C with the help of the Pt-100 resistor. A second-order polynomial was extracted from the measurements for each temperature sensor providing the temperature coefficients i and a2.  

The calibration was done for temperatures between 25 °C and 325 °C. The data were fitted according to Eq. (4.1), and the two temperature coefficients were extracted. Within the same wafer batch, a production-spread-induced error of 2% in the determination of the microhotplate temperature coefficients was observed. 

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The accuracy and precision of melting point determinations depend on several factors. Calibration of the temperature sensor is the first and... 

Ideally, the energy equivalents e and f should be measured over the same temperature range of the reaction ran, to avoid errors from their variation with temperature and to achieve maximum compensation for errors in the calibration of the temperature sensor [26,128,129], These errors are, however, frequently negligible in the temperature ranges involved, and the measurement of or f is normally performed outside the Jj -> Tf interval. This procedure saves time because there is no need to readjust the initial temperature of the calorimeter between the calibration and main experiment runs. It is therefore a common practice, even when an exothermic reaction is studied, to measure before the reaction and ef after the reaction and adjust the experimental conditions so that Jr is the midpoint between J] and Tf. In this case, the temperature of the thermostatic... 

Make certain that reactor is empty by looking through glass port on top of vessel. Call an instrument person to verify the calibration of the temperature sensors. 

This latter point begs the question Who can verify the accuracy of a reference point if its value may vary In other words, who is the ultimate source of calibration materials, such as a thermometer In the U.S., it is the National Institute of Standards and Technology (NIST). This is the same organization that we cited as the source of accurate standardization materials in Chapters 3 and 4. Experiments 16 and 17 in this chapter are exercises in the calibration of a temperature sensor and how such a calibrated sensor can be used. 

A schematic view of the microhotplate functional elements is presented in Fig. 4.4. A resistive temperature sensor is embedded in the heated area of the microhotplate. The resistance is measured in a four-point measurement The calibration procedure of the temperature sensor will be explained in the next section (Sect. 4.1.4). The heating power dissipation is determined using also a four-point configuration. The external wiring of the heater typically adds another 5% to the heater resistance, which has to be eliminated for an accurate measurement of the dissipated power. A heating current, /heat, is applied, and the voltage drop, Vheat. across the heater is measured on chip. 

Selection of the temperature sensor or sensors to be used in the test stand is influenced by many factors. The important point to remember here is that, in general, probe manufacturers will not have the extensive facilities necessary to provide sufficient performance data to facilitate an evaluation of all the characteristics you may consider important. This is especially true for liquid hydrogen measurements and adds emphasis to the fact that you must have your own calibration facilities. 

In calorimetric measurements, the location of the temperature sensor is generally fixed, while those of the calibrating heat source and the heat source of the examined process can differ. If the temperature of the other domains is measured, it is without difference in that one in which only the calibrating effect and the heat effect process are situated because there is equivalence of the heat sources and/ n = Rn- On the other hand, when the temperature is measured in the inner domain, the calibrations and examined heat effects must occur in the same domain because 21 Rii-... 

In situ calibration of the conductivity sensor starts with calibration of the temperature and pressure values in the up profile at bottle closing pressures. Next, in situ reference conductivity Cref is derived from bottle salinity 5ref, T and P. ff necessary, Ccro is compensated for pressure and temperature effects according to Eq. (3-14). The final correction Cc=Cref-Ccc depends on the sensor and the type of the CTD and on Ccxi the drift in terms of a group of cast numbers may be included and further pressure correction may be needed. As an example, the corrected conductivity C may be written as ... 

A 1.1 Principle—This section of the Annex deals with the basic calibration of the vapor temperature sensor against primary temperature standards as recommended by the National Institute for Science and Technology (NIST) in order to avoid the problems associated with the use of secondary temperature references. It can also be used for the calibration of other temperature sensors. 

The tip of the temperature sensor shall be located above the top of the packing or the topmost glass plate and in close proximity to the reflux divider but not in contact with the liquid reflux. The location must be proved by the method described in Annex A4. It shall have a cooling time of not more then 175 s as described in Annex A5. The sensor must be calibrated as described in Annex A6. The vapor temijera-ture is measured to the nearest 0.5°C and recorded either manually or automatically. 

Temperature Sensors The traceability/accuracy issue of temperature sensors is well understood. A common policy is to claim an uncertainty in the measured value (the blackbody temperature in our case) no better than 4 or 10 times the uncertainty in their instrumentation. For example, if we believe the calibration of our temperature sensor is within 0.5 K, the metrology group would not be willing to certify the blackbody temperature to better than 2 K (4 1) or 5 K (10 1). 

The development of an SCR system for vehicle applications requires precise calibration of the amount of urea injected as a function of the quantity of NO emitted by the engine, exhaust temperature and catalyst characteristics. Although model simulations can help in the control, it is necessary to use specific NO sensors which, however, still have problems of sensitivity and transient response. Installing a clean-up catalyst for ammonia would provide more latitude and obtain higher NO conversion ratios without re-emission of ammonia into the atmosphere. 

Routine calibration of an NO sensor is essential in order to ensure accurate experimental results. One of three calibration techniques is generally used, depending on the sensor type, and will be described in the following section. Each of these methods has already been the subject of several reviews [23, 72-74] and will therefore only be summarized here. NO sensors are typically sensitive to temperature. Therefore, calibration is usually best performed at the temperature at which the measurements will be made. 

Two identical polysilicon temperature sensors with a nominal resistance value of 10 kQ are located in the membrane center. One resistor is connected to the temperature controller, the other sensor is totally decoupled from the circuitry. This second temperature sensor can be directly accessed via bond pads in a four-point configuration. It enables an accurate calibration and a verification of the temperature controller... 

All required sensors (temperature, pressure, conductivity, how meter, etc.) in contact with the process waters must be the sanitary type, connected by tri-clamp, and well mounted (temperature). The length of the electrical connections must be long enough to allow the calibration of the sensors. 

The isopiestic and manometric methods (units A2j A2.4) for determination of water activity have the limitation of being dependent on fixed laboratory equipment. The electronic-type sensors have advantages of portability, speed, and simplicity of measurement. The characteristics of a sensor depend upon the manufacturer and each instrument must be calibrated separately. The anodized sensors have advantages of ruggedness, small dimensions, and fast response, as well as freedom from large temperature coefficients and less susceptibility to contamination of the lithium chloride conductivity sensors (Smith, 1971). 

In order to use the sensor on an industrial scale, an appropriate housing is needed in which the required electrodes and temperature sensor are positioned in the scientifically and technically most considered and logical way. Additional requirements imply that the system should be robust and offer good protection against blows and/or other possible causes of defects. The system should be easy to handle, electrodes and other components should be straightforward to replace, the calibration of the electrodes should be accomplishable in a quick and particularly simple way, and the system must... 

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