Pressure sensor chip

Description > j K-ssries pressura ssrt ofs feature LPSi-NT Series and MPSi-NT Series pressure sensor chips mourned cn TOB-headers. 

In the following, we describe a chemical sensor combining a smart hydrogel and a micro fabricated pressure sensor chip for continuously monitoring the analyte-dependent swelling of a hydrogel in aqueous solutions. 

Figure 1 illustrates the operational principle of hydrogel-based sensors. Pressure sensor chips with a flexible thin silicon bending plate and with an integrated piezoresistive Wheatstone bridge inside this plate have been employed as... 

Fig. 2. Digital pressure sensor on a 6 x 4.8 mm chip, fabricated at the Technical University of Berlin (5). See text.

Die Fabrik auf dem Chip, Spektrum der Wissenschafi, October 2002 Miniaturization and modularization of parts of future chemical apparatus general advantages of micro flow expert opinions specialty and fine chemical applications leading position of German technology flexible manufacture large-capacity micro reactors reformers for small-capacity applications compatible and automated micro-reaction systems process-control systems temperature and pressure sensors [209]. 

Pressure sensors that give temperature-corrected, linear, analog voltage output are available from Motorola and other manufacturers. In such sensors, the on-chip electronics correct any temperature effects and nonlinearities in the output of the piezoresistors. The on-chip electronics replace a shoebox-size collection of printed circuit boards. The price of this kind of smart sensor is considerably less than 100. The integration of a large amount of circuitry on the chip allows functions like amplification, offset correction, self-testing, autocalibration, interference reduction, and compensation of cross-sensitivities (6). 

FIGURE 7.15 Schematic of a plasma emission chip consisting of the top and bottom plates. Features of the bottom plate (20 x 30 x 0.5 mm) are 1, gas inlet 2, gas outlet 3, pressure sensor connection 4, electrodes 5, electrode connection pads. Etched in the top plate (14 x 30 x 0.5 mm) are 6, plasma chamber 7, inlet channel 8, outlet channel [718). Reprinted with permission from the Royal Society of Chemistry. 

The amount of electrons extracted from the microplasma, the ionization rate of the sample gas, and the mean free path length depend on the pressure at the different locations of PIMMS-chip. Therefore, exact knowledge and control of pressure and gas flow rates will be necessary for quantitative analysis. Pressure sensors, valves for gas inlets, and vacuum pumps are the components, which have to be read out and controlled, respectively, by electronic and software to install and stabilize appropriate pressure regimes. 

Microdielectrometry was introduced as a research method in 1981 14 and became commercially available in 1983 20). The microdielectrometry instrumentation combines the pair of field-effect transistors on the sensor chip (see Sect. 2.2.3) with external electronics to measure the transfer function H(co) of Eq. (2-18). Because the transistors on the sensor chip function as the input amplifier to the meter, cable admittance and shielding problems are greatly reduced. In addition, the use of a charge measurement rather than the admittance measurement allows the measurements to be made at arbitrarily low frequencies. As a matter of practice, reaction rates in cure studies limits the lowest useful frequency to about 0.1 Hz however, pre-cure or post-cure studies can be made to as low as 0.005 Hz. Finally, the differential connection used for the two transistors provides first-order cancellation of the effects of temperature and pressure on the transistor operation. The devices can be used for cure measurements to 300 °C, and at pressures to 200 psi. 

The aim is to eliminate entrance effects as much as possible and any influence on the flow of the pressure tap holes into the channels. This was achieved by integrating on the same silicon chip the microchannel, the pressure taps and the pressure sensors. The fabrication process and the operating mode are described in [28]. The pressure sensors are constituted cf a membrane which is deformed under the fluid pressure and on which is deposited a thin film strain gauge. This strain gauge forms a Wheatstone bridge whose the membrane deformation modifies the electrical resistances. 

Fig. 5.1.16 Piezoresistive pressure sensor made by silicon fusion-bonding (SFB) to obtain small chip size and anodic bonding to form a sealed vacuum cavity...

Fig. 5.1.17 Absolute pressure sensor for good media compatibility with pressure inlet port on the bottom of the silicon diaphragm and an on-chip vacuum reference volume, made possible by triplestack anodic bonding...

Fig. 5.1.19 Silicon pressure sensor (left) and accelerometer (right) on the same chip, made possible by one of SensoNor s standardized sealed-cavity processes...

When a built-in self test is not feasible, we encounter difficulties because primary input signals cannot be easily provided within a standardized probe setup. To our knowledge, no commercial testing equipment is available that allows a set of primary stimuli like acceleration, pressure, torque, or mass flow to be applied to the transducer elements of sensor chips on the wafer level, with the required speed and precision. At the moment we are therefore left with purely electrical stimuli for testing microsensor devices. 

Fig. 6.2.14 shows the chip photo of the realized signal processing ASIC for high-pressure sensors. The signal conditioning operates in the above described manner. The parameters of the sensor are as follows ... 

To develop any sensor with the potential to replace the piezoresistive pressure sensor, it is essential to impart the ability to detect the same physical quantity from very low to high pressure, to employ micromachining technology, and to produce a simple one-chip package [11]. If these goals can be achieved, the prospect of combining reduced cost with a many-fold increase in the number of pressure sensor applications per vehicle may no longer be a dream. 

FIGURE 2.6 Silicon chip pressure sensors for biomedical applications (a) a typical clinical pressure sensor and (b) a cross sectional view of a silicon chip-based biomedical pressure sensor. 

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