Abstract: A method and apparatus for measuring the velocity of a fluid relatively independently of the physical properties of the fluid. This is preferably accomplished by spacing two sensor elements at different distances from a heater element. The present invention also contemplates minimizing the effects of the non-zero heater time lag and/or the non-zero sensor time lag for increased accuracy. This is preferably accomplished by either measuring the time lags and subtracting the values thereof from an uncorrected transit time measurement, forcing the sensor elements to track the thermal disturbance in the fluid thereby minimizing the effects of the sensor time lags, or measuring the transit time using sensors that have substantially zero thermal mass.

Abstract: A method and apparatus for determining selected fluid properties including thermal conductivity, pressure and/or temperature using a single heater element of the sensor, and in a relatively short period of time. This is accomplished by measuring a variable phase or time lag between an input signal provided to the heater element and a subsequent transient temperature response of the heater element.

Abstract: A method and apparatus for providing a more direct approach to determine the thermal conductivity, thermal diffusivity and specific heat of a fluid of interest, independently of the amplitude of the sensor output. This is preferably accomplished by measuring one or more variable phase or time lags between selected input and output AC signals, and directly deriving the thermal conductivity, thermal diffusivity and specific heat therefrom. Such derivation is therefore less dependent than amplitude-based sensors on occasional or unpredictable drift in sensor resistive elements.

Abstract: Transducer apparatus and related method are described for substantially simultaneously determining pressure and one other property (or property combination) of a flowing gas of varying pressure and composition. The technique utilizes several empirical algorithms for correlating the frequency and series resistance of a crystal resonator exposed to the test gas with the desired properties. The apparatus and method can be readily incorporated into an on-line heating value determination process such as that set forth in the referenced co-filed application.

Abstract: A selective gas detecting apparatus for determining the concentration and type of hydrocarbon gas in a gas sample based upon absorption of infrared radiation by the gas sample, the apparatus having two infrared radiation absorption channels with the wavelengths for measurement selected so that one channel at 3.2 microns provides an output signal corresponding to approximately the sum of all hydrocarbons in the gas sample which signal is displayed as an indication of concentration of hydrocarbon gas in the gas sample, and the other channel at 3.4 microns, after essentially being ratioed to the 3.2 micron channel output provides an output signal representative of the type or average type of hydrocarbon in the gas sample, and the ratio of the signal in the two channels is displayed as an indication of the type of hydrocarbon in the gas sample.

Abstract: A method and apparatus for accurate low noise demodulation of a modulated multi-signal input waveform. The multi-signal input waveform includes a plurality of sequential signal pulses, each pulse having a first adjacent background signal immediately preceding it and a second adjacent background signal immediately following it in time. The invention provides apparatus for synchronously separating the sequential signal pulses and apparatus for synchronously demodulating each sequential signal pulse. The separating apparatus separates each sequential signal pulse together with its adjacent background signals into one of a plurality of channels according to the sequence order of the pulse. Once the sequential signal pulses are separated into separate channels together with their background signals, the demodulating apparatus in each channel averages the first and second adjacent background signals for each pulse to yield an adjacent average background signal.

Abstract: A selective gas detecting apparatus for determining the concentration and type of hydrocarbon gas in a gas sample based upon absorption of infrared radiation by the gas sample, the apparatus having at least two infrared radiation absorption channels with the wavelengths for measurement in the two channels selected as 3.2 microns and 3.4 microns, signals in the two channels being processed to formulate an indication of absorbance of hydrocarbons at the selected wavelength, the absorbance signal in one channel being displayed as an indication of concentration of approximately the total hydrocarbon gas in air and the ratio of absorbances being displayed as an indication of the type of hydrocarbon in air and independent of the concentration of the gas.

Abstract: A method and apparatus for determining both the thermal conductivity, k, and specific heat, c.sub.p, of a fluid of interest are disclosed. An embodiment uses proximately positioned resistive heater and thermal sensor coupled by the fluid of interest. A pulse of electrical energy is applied to the heater of a level and duration such that both a transient change and a substantially steady-state temperature occur in the sensor. The k of the fluid of interest is determined based upon a known relation between the sensor output and k at steady-state sensor temperature; and c.sub.p of the fluid of interest is determined based on a known relation among k, the rate of change of the sensor output during a transient temperature change in the sensor and c.sub.p.

Abstract: Changes in the output frequency of a voltage controlled oscillator circuit due to temperature changes are compensated for by shunting a resistor with two series diode resistor combinations. The variation in the diodes' voltage drip with temperature provides a resistance that varies with temperature, to correct for other resistance or capacitive changes with temperature in the circuit, thereby obtaining a more stable oscillator frequency in a varying temperature environment. Compensating for temperature effects by shunting a resistor with a means whose resistance decreases with temperature is a method applicable to circuits other that oscillators.

Abstract: A voltage controlled oscillator circuit is provided wherein the frequency of the output is increased or decreased by a .+-.DC control voltage centered at 0 VDC. The output of the oscillator has a constant on/off ratio and the ratio holds constant over the frequency control range.

Abstract: An electrical control circuit includes a first energy storage means adapted to store electrical energy in response to a potential source of a first polarity relative to a reference point in said circuit, thereby providing a first voltage of a first magnitude; a second energy storage means adapted to store electrical energy, without affecting said first energy storage means, in response to a potential source of a second polarity relative to said reference point, thereby providing a second voltage of a second magnitude; and means for electrically connecting said first and second energy storage means so as to provide an output voltage related to the sum of said first and second magnitudes. Four embodiments are presented with two embodiments arranged so that substantial voltage is supplied to a load only when said first and second energy storage means are connected by an electrical connecting means.

Abstract: A stable alignment mechanism for laser mirrors has a resilient diaphragm integrally formed between a base and a support for the laser mirror. An adjusting screw or screws rotate the support with respect to the base to align the mirror.