Pt temperature sensor

The third microhotplate introduced in Sect. 4.3 was designed to extend the operation temperature limit imposed by the CMOS-metallization contacts in the heated area. A new heater design was devised, and a microfabrication sequence that enables the realization of Pt temperature sensors and Pt-electrodes was developed. This microhotplate was also monolithically integrated with circuitry as presented in Sect. 5.2, and operating temperatures of up to 500 °C have been achieved. 

Fig. 4.12. Micrograph of the microhotplate with Pt temperature sensor Table 4.4. Design parameters of the high-temperature microhotplate... 

Fig. 4.14. Schematic ofthe microfabrication process for the high-temperature microhotplate with Pt temperature sensor...

This chapter includes two different sensor system architectures for monolithic gas sensing systems. Section 5.1 describes a mixed-signal architecture. This is an improved version of the first analog implementation [81,91], which was used to develop a first sensor array (see Sect. 6.1). Based on the experience with these analog devices, a complete sensor system with advanced control, readout and interface circuit was devised. This system includes the circular microhotplate that has been described and characterized in Sect. 4.1. Additionally to the fabrication process, a prototype packaging concept was developed that will be presented in Sect. 5.1.6. A microhotplate with a Pt-temperature sensor requires a different system architecture as will be described in Sect. 5.2. A fully differential analog architecture will be presented, which enables operating temperatures up to 500 °C. 

Fig. 5.16. Micrograph of the sensor microsystem with integrated Pt temperature sensor for operating temperatures up to 500 °C...

Fig. 5.21. Sensor response of a sensor system featming a Pt-temperature sensor upon exposme to CO. The microhotpiate temperature was 290 °C, and the measurements were conducted at 40% r.h.

The main goal of another microhotplate design was the replacement of all CMOS-metal elements within the heated area by materials featuring a better temperature stability. This was accomplished by introducing a novel polysilicon heater layout and a Pt temperature sensor (Sect. 4.3). The Pt-elements had to be passivated for protection and electrical insulation, so that a local deposition of a silicon-nitride passivation through a mask was performed. This silicon-nitride layer also can be varied in its thickness and with regard to its stress characteristics (compressive or tensile). This hotplate allowed for reaching operation temperatures up to 500 °C and it showed a thermal resistance of 7.6 °C/mW. 

To overcome the temperature limits of CMOS integrated systems that are imposed by, e.g., the degradation of the CMOS metallization, a microhotplate with Pt-temperature sensor was also monolithically integrated with circuitry so that the hotplate operating temperature range could be extended to 500 °C (Sect. 5.2). The read-out of the comparatively low Pt temperature sensor resistance required the integration of a fully differential amplifier architecture. 

Err" signal errors are automatically shown on the LED display in the case of a defective pH electrode or faulty temperature sensor (Pt 100) and for incorrect buffer two set points can be set over any part of the pH, mV or 0° C scale, which when exceeded starts an alarm and/or allows readjustment of dosing valves or pumps via an interface circuit. 

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. ... 

A novel microhotplate design was proposed to overcome the CMOS operating temperature limit and to avoid polysilicon-induced drift problems. A cross-sectional schematic of the device is shovm in Fig. 4.11. Instead of using a polysilicon resistor as temperature sensor, a platinum temperature sensor is patterned on the microhotplate. The Pt-metallization process step was used to simultaneously fabricate the electrodes and the temperature sensor. The CMOS-Al/Pt contacts are located off the membrane... 

The limit for the operating temperature of CMOS-microhotplates can be extended by using the microhotplate that was presented in Sect. 4.3. We now detail high-temperature microhotplates with Pt-resistors that have been realized as a single-chip device with integrated circuitry. While the aluminum-based devices presented in Sect. 4.1 were limited to 350 °C, these improved microhotplates can be heated to temperatures up to 500 °C. As the typical resistance value of the Pt-resistor is between 50 and 100 Q, a chip architecture adapted to the low temperature sensor resistance was developed. The system performance was assessed, and chemical measurements have been performed that demonstrate the full functionality of the chip. 

For the characterization of the sensor system, the voltage drop across the Pt-resistor and the chip-temperature sensor have been read out with multimeters. The input con-... 

Figure 2.38 Schematic of the suspended-tube reactor (left and middle) and SEM (right) showing four suspended SiNx tubes connected to the Si reaction zone, Si slabs thermally linking the four tubes and a meandering Ti/Pt resistive heater/temperature sensor [72] (by courtesy of L. R. Arana).

Rotor critical motors with temperature sensors in the rotor require expensive data transmission techniques, e.g. Pt 100 resistances, data convertor with frequency modulator, and brushless data transmission to a stator-fixed... 

In many applications, temperatures of stator windings and bearings of motors are continuously monitored during operation by Pt-100 resistance thermometers or PTC (positive temperature coefficient) temperature sensors. 

E.D. (2006) Temperature-programmed reaction and desorption of the sensor elements of a WOa/YSZ/Pt potentiometric sensors. J. Electrochem. Soc., 153 (6), H115-21. 

Fig. 15. Schematic presentation of the sensor (a) measuring electrode design coated with zeolite film (top) and heater electrodes (bottom), (b) cross section. The resistance of the Pt heater is also used as temperature sensor. [ 1271...

In power compensated DSC the small size of the individual sample and reference holders makes for rapid response. The temperature sensors are platinum (Pt) resistive elements. The individual furnaces are made of Pt/Rh alloy. It is important that the thermal characteristics of the sample and reference assemblies be matched precisely. The maximum operating temperature is limited to about 750 °C. High temperature DSC measurements (750-1600°C) are made by heat flux instruments using thermocouples of Pt and Pt/Rh alloys. The thermocouples often incorporate a plate to support the crucible. The use of precious metal thermocouples is at the expense of a small signal strength. Both chromel/alumel and chromel/constantan are used in heat flux DSC equipment for measurements at temperatures to about 750 °C. Multiple thermocouple assemblies offer the possibility of an increased sensitivity - recently a 20-junction Au/Au-Pd thermocouple assembly has been developed. Thermocouples of W and W/Re are used in DTA equipment for measurements above 1600°C. The operating temperature is the predominant feature which determines the design and the materials used in the con-... 

PT 100 temperature sensor and miniaturized high-pressure transducer... 

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