Abstract:
A circuit produces an output that is proportional to the molar density of gas in a chamber. The circuit employs an operational amplifier which measures the temperature using a RTD or other element that changes resistance with temperature. The RTD is placed such that it produces a decreasing current draw at the inverting input of the operational amplifier as the temperature increases. This decreasing current draw in turn produces a decreasing voltage at the output of the operational amplifier. By changing the ratio of resistors connected to the non-inverting terminal of the operational amplifier one changes the offset of the output voltage. By changing the feedback resistor connected from the output of the operational amplifier to the inverting terminal and connecting the output of the inverting terminal to a voltage divider including the RTD device, one can change the gain with temperature. Thus the output voltage of the operational amplifier is carefully controlled to be proportional to 1/T for many different temperature scales and ranges. The output of the amplifier serves as the biasing voltage for a pressure transducer.
Abstract:
A personal identification system employs a matrix of pressure sensors mounted to a plate having a template of a human hand. When a person's hand is placed on the plate and overlying the template a pressure profile of the person's hand is provided. This profile is compared with a stored pressure profile of the same person's hand. If the pressure points or profiles correlate a positive identification of the person is made.
Abstract:
A high temperature pressure sensing system (transducer) including: a pressure sensing piezoresistive sensor formed by a silicon-on-insulator (SOI) process; a SOI amplifier circuit operatively coupled to the piezoresistive sensor; a SOI gain controller circuit including a plurality of resistances that when selectively coupled to the amplifier adjust a gain of the amplifier; a plurality of off-chip contacts corresponding to the resistances, respectively, for electrically activating the corresponding resistances and using a metallization layer for the SOI sensor and SOI ASIC suitable for high temperature interconnections (bonding); wherein the piezoresistive sensor, amplifier circuit and gain control circuit are suitable for use in environments having a temperature greater than 175 degrees C. and reaching between 250° C. and 300° C., and wherein the entire transducer has a high immunity to nuclear radiation.
Abstract:
A silicon wafer is fabricated utilizing two or more semiconductor wafers. The wafers are processed using conventional wafer processing techniques and the wafer contains a plurality of output terminals which essentially are platinum titanium metallization or high temperature contacts. A glass cover member is provided which has a plurality of through holes. Each through hole is associated with a contact on the semiconductor wafer. A high temperature lead is directed through the through hole or aperture in the glass cover and is bonded directly to the appropriate contact. The lead is of a sufficient length to extend into a second non through aperture in the contact glass. The non through aperture is located on the side of the contact glass not in contact with the silicon sensor. The non through aperture is then filled with a high temperature conductive glass frit. A plurality of slots are provided. Each slot is associated with a through and a non through aperture to accommodate the wire as directed from the through aperture through the slot and into the non through aperture. The slots provide means of retaining or securing the wire as it passes from the through aperture to the non through aperture. The non through apertures as indicated are filled with a high temperature conductive glass frit which glass frit accommodates suitable pins.
Abstract:
There is disclosed an electronic single pole double throw switch which completely replaces a prior art mechanical switch. The mechanical switch normally exists in a suitable vehicle, such as an aircraft or any device, but basically has three output terminals. Two terminals are associated with a first and a second lamp, which lamps have one terminal coupled to an operating voltage. Essentially, in order to replace the mechanical switch, an electronic switch also is wired to the three terminals exactly as a mechanical switch would be so wired. The electronic switch has two states. In each state, one of the lamps is on and the corresponding switch is closed. In this state, the other lamp is off, with its corresponding switch open. This operation is the same operation as that of the mechanical switch. In the electronic switch, the voltage, which is at the output terminal of the lamp that is off, is utilized to drive a low voltage regulator which operates electronic circuitry associated with the electronic switch. The electronic switch contains a timing oscillator which produces a pulse of a narrow interval. This narrow pulse is utilized to supply operating potential to a piezoresistive bridge circuit. The activation of the bridge circuit causes the bridge circuit to produce an output during the pulse interval, which output is directed to a differential amplifier and then to a comparator. The comparator receives an operating voltage during the pulse interval and compares the pressure of the bridge circuit against a threshold pressure. If this threshold pressure is exceeded, the comparator causes a flip-flop to change state. The flip-flop has first and second outputs, each coupled to an associated switching circuit. Each switching circuit will activate an associated lamp to cause the lamp to illuminate when the flip-flop is in a given state. The state of the flip-flop can be changed during the next pulse interval if the pressure applied to the bridge circuit changes.
Abstract:
There is disclosed a transducer with an integral switch for wireless electronics. Essentially, the transducer contains a housing which includes a sensor device. The sensor device may be a piezoresistive Wheatstone bridge arranged in a conventional manner. The output of the bridge is coupled to a typical amplifying circuit or an analog-to-digital converter whose signal is coupled to a suitable transmitting means. The signal provided by the Wheatstone bridge is transmitted through RF, infrared or some other wireless transmission scheme to a remote location. Such transmissions schemes are well known. Associated with the sensor and secured to the sensor housing, is a push button switch which is wired in series with a battery. The battery operates to energize the sensor, including all the electronics when the sensor is in placed in a pressure sensing position. When the pressure is placed in a pressure sensing position, the push button switch, is actuated to apply operating bias to the transducer device.
Abstract:
A solid state fuel cell is fabricated from three substructures. There is a nanostructure porous semiconductor anode which is surrounded by a non-porous ring. The pore size of the anode material is sufficiently large to allow hydrogen gas to flow through and is of a sufficiently high conductivity to easily permit current flow of electrons. One side of the anode has a layer of titanium and platinum catalyst sputtered or otherwise deposited on the surface with the pores to produce a coated surface with the catalyst entering and coating the walls of the pores. A cathode is made in a similar manner and is fabricated as is the anode. There is a center electrolytic section made from a low conductivity semiconductor material. The center electrolytic section has the coated side of the anode secured to one side and has the coated side of the cathode secured to the other side. The other or un-coated face of both the anode and the cathode has an electrical contact secured thereto to permit electrons to leave the anode and to reenter the cathode. The electrolytic center structure is filled with an ionic conductor. In this manner, hydrogen is broken into ions and electrons. The electrons cause a current flow, while the ions react with oxygen and produce water which is discharged from the fuel cell as steam or vapor.
Abstract:
A displacement transducer includes a load cell structure having a thick outer peripheral area, a thick inner central area and two symmetrical thin beams. The two beams are disposed along a common diameter of the structure and joins the outer peripheral area and the inner central area. At least one strain gauge is placed on a surface of one beam and at least one strain gauge is placed on a surface of the second beam. A top diaphragm cover member is secured to a top surface of the outer peripheral area and covers the two beams.
Abstract:
A high temperature pressure capacitor is fabricated utilizing two high temperature substrate wafers. The substrates may be silicon carbide (SiC) or aluminum nitride (AIN). The first substrate has a metal conductive plate positioned on a top surface thereof. The top surface and plate are covered with a dielectric layer. The second substrate has a plate accommodating recess on the top surface thereof. Deposited in the recess is a second conductive plate. The first and second wafers are bonded together via the dielectric layer where the first and second plates face each other. Upon application of a force to the first wafer the diaphragm portion of the first wafer deflects causing the first plate to move and thereby varying capacitance. An inductor may be fabricated on a bottom surface of the second wafer to provide an LC circuit whose resonant frequency varies as a function of capacitance and therefore as a function of pressure.
Abstract:
A method and apparatus for measuring knocking in internal combustion engines employs a high temperature transducer, which transducer is mounted within a cylinder. The output of the transducer is solely related to pressure. The output signal from the transducer is directed to the input of a high frequency amplifier associated with a band pass filter. In this manner the combustion signal can be filtered out and one provides a signal which is only indicative of the knocking signal and of the knocking frequencies. This signal can be analyzed simply and effectively by the use of a processor such as a multimeter or a microprocessor. In a similar manner the processor can compare the combustion and knocking signal without the band pass filtering with the knocking signal with the combustion signal filtered out.