Platinum heaters

It is necessary to maintain close control over temperature because of its effect upon the base resistance of the semiconductor. With a platinum heater this can be effected to 0.1 °C through monitoring the resistance of the heater itself using a Wheatstone bridge. The relatively high temperature coefficient of resistivity of Ru02 complicates the control system. 

The central heater is made up of a platinum heater assembly within an alumina or mullite sheath.1 Voltage taps symmetrically placed about the center allow determination of power per unit length dissipated radially past the inner and outer ther-... 

Fig. 11 Scanning electron microscopy photos of microreactor produced by Jensen et al. for reforming of ammonia showing four freestanding SiN tubes, a suspended Si reaction zone with integrated thin-film platinum heater and temperature sensing resistor (TSR), and Si slabs wrapped around the four tubes. (From Ref.P l)...

An early example of an integrated gas sensor array is a thick-film implementation developed by Hitachi [49], with six discrete metal oxide sensor areas on an alumina substrate (figure 14.5). The chip is heated to 4(K) °C with a platinum heater printed on the bottom of the substrate. More recently, other Sn02-based arrays have been reported. A low-power, 1.5 mm foursensor array employing Sn02 has been demonstrated for detection of toxic... 

Another technique, used by Figaro Engineering Inc. and others, is to coat an alumina tube with tin oxide in an organic matrix, such as stearic acid, and sinter at 400-700 °C. A porous film results. Electrodes at either end of the tube are printed on or embedded in the sintered oxide and a platinum heater coil is positioned inside the tube. 

Fig. 4 Photographs of p-DAAD production steps, (a) Front side of a 4" silicon wafer populated with etched microreactors 16 p-DAAD are processed in parallel, each consisting of four microreactors. (b) Front-side view of a single p-DAAD (16 x 1 mm ) after bonding a cover plate and dicing. DNA arrays are printed onto the bottom of the microreactor cavities, but carmot be seen in this image because of their small size. Holes of 1 mm in diameter are drilled in the cover glass for the filling of the p-DAAD reactors with reagent, (c) Back-side view of the device with platinum heater coil and thermoresistors placed at the corresponding area of the microreactor. Reproduced from [79] with permission...

Chlorofluorocarbon can be measured with usual electrochemical halogen sensors after decomposing chlorofluorocarbon with a platinum heater. Fig. 16... 

Figure 1.8a showed a scheme of the CNTs NO2 sensor layout for NO2 detection with limits as low as 10 ppb [108], It was prepared by a radio frequency plasma enhanced chemical vapour deposition (r.f. PECVD) on Si/Si3N4 substrates. The thin film (5 nm) of Ni catalyst was deposited onto Si3N4/Si substrates provided with platinum interdigital electrodes and a back-deposited thin-film platinum heater... 

New-generation micro-resistive sensors are usually formed on a thin thermally-insulated silicon membrane so as to reduce the power loss this thin membrane-like structure is often referred to as a micro-hotplate . Researchers have studied different materials for designing micro-heaters, such as doped polysilicon, aluminium and platinum (Cavicchi et al, 1995 Houlet et al, 2006 Udrea et al, 2001). Platinum heaters are probably the most stable material at 400°C, but this material is not available in a CMOS foundry hence, post-CMOS deposition is necessary. Within the CMOS... 

Figure 5.9 Schematic cross-section of a power compensated differential scanning calorimeter (modified from Robie (1987)). R - reference S - sample. Under each sample pan is a platinum resistance thermometer and a platinum heater. The large metal block helps to keep the temperatures in the two chambers equal.

Figure 16 Power-compensation DSC schematic depicting individual platinum heaters and sensors. Power-compensation DSC is typically used for very exact calorimetry work which demands accuracy as well as precision. It is used for fast quenching experiments such as subtle determination as well as melting studies and specific heat studies. It is also used for routine analysis.

The insulation strategy for the device was vacuum packaging, which is in line with other small scale system designs described above. A micro-fixed bed steam reformer coupled to a preferential oxidation reactor was then developed by Shah and Besser with a theoretical power output of 0.65 W. The heat supply of the combustion reaction was simulated by the platinum heater, as shown in Figure 9.19. The BASF commercial steam reforming catalyst was milled to 70 pm and introduced into the device by pneumatic transport, filter structures retained the particles within the device. Fleating experiments revealed that the steam reformer could not be heated to more than 230 °C by the electric heater, which had reached a temperature of 550 °C even under these conditions. This was attributed to heat losses by various mechanisms. Insulation by fibreglass decreased the heat losses substantially. The conclusion of... 

The Nernst lamp bulb was nearly 80% more efficient than the carbon fiber bulb. But it was difficult to produce reliable contacts for the glower and the platinum heater made the lamp very expensive. Glowers also had to be protected from melting by special isolators. Turning on the lamp s glow took about half a minute. The Nernst lamp was the first commercially produced solid electrolyte gas cell (Table 1.2). 

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