Abstract: Pressure sensors and their methods of use are described. In one embodiment, a pressure sensor may include: a tubular probe body; a capacitive sensor disposed at the distal end of the probe body; a lead electrically coupled to the sensor extending along an interior space of the probe body; and at least one support formed of a material having a relatively low dielectric constant disposed within the probe body to support the lead and space the lead away from an inner wall of the probe body. This may help to minimize shunt capacitance and changes in shunt capacitance due to radial movement of the lead. In other embodiments, a pressure sensor may include a channel formed in a wall of the probe body, a temperature sensor disposed at a distal end of the probe body, and a temperature sensor lead disposed in the channel and connected to the temperature sensor.

Abstract: High temperature pressure sensing devices and methods are disclosed. In some embodiments, a high temperature pressure sensor including intrinsic zero output and span correction versus temperature is disclosed. In addition, ways in which to improve high temperature performance through the use of intermediate circuits located towards the distal end of the high temperature pressure sensor as well as configurations to reduce thermally induced stresses within the pressure sensor are disclosed. The disclosed embodiments also detail ways in which to reduce signal loss due to various stray capacitances within the pressure sensor to improve signal fidelity and sensitivity.

Abstract: A tunnel diode voltage reference circuit includes a tunnel diode; bias voltage circuit for biasing the tunnel diode to operate in the region of the peak current where the tunnel diode output current variation is a fraction of the bias voltage variation; and circuits responsive to the tunnel diode output current, for isolating the tunnel diode output from load variations and converting the tunnel diode output to a reference voltage. A resistance may be placed in parallel with the tunnel diode for raising the negative resistance region to the levels of the peak region to flatten the slope of the negative resistance region between the peak and the valley regions, reducing the reference voltage variation at bias points greater than the peak voltage of the tunnel diode characteristic.

Abstract: A negative resistance device local extremum seeking circuit including a negative resistance device (NRD) and a biasing device for providing a bias signal to operate the NRD. The output of the NRD is detected by a detector that provides a signal which indicates the position of the bias signal in relation to the peak of the NRD. A bias adjust circuit responsive to the detector adjusts the bias signal toward the peak of the NRD to operate it at the peak.