Abstract: A method and apparatus in which a first absorption measurement is made over a first frequency interval or set of frequency intervals including one or more absorptions from a spectral band of interest. The first absorption measurement is ideally selected to be near the frequency of a peak in the absorption spectrum, providing high sensitivity at low gas concentrations. A second absorption measurement is made over a second frequency interval. The second absorption measurement is made to include a contribution from the broadening of the absorption spectrum at higher concentrations. The second absorption measurement provides sensitivity at higher concentrations. The two absorption measurements are then combined to deduce the target sample concentration as the absorption line spectrum changes shape with concentration.

Abstract: An obstacle avoidance system for obstacle detection in an opaque material. The system includes at least one electromagnetic signal source adapted to produce an electromagnetic source signal suitable for transmission through the opaque material, at least one electromagnetic signal detector adapted to receive reflected electromagnetic energy signals from discontinuities in the opaque material encountered by the electromagnetic source signal, and a reflected electromagnetic energy signal processor suitable for determining a presence of obstructions and/or strata variations within the opaque material. The system is preferably integral with a head element suitable for traversing the opaque material, for example a subterranean drill bit.

Abstract: A temperature time-of-flight (TOF) sensor is combined with a nozzle of known flow area to create a TOF flowmeter. The TOF measured by the flow sensor provides a measure of gas volumetric flow rate. A TOF sensor has of a pulse heated wire and a single temperature sensor downstream of the wire. This single temperature sensor arrangement allows the accurate measurement of gas velocities much lower than the previously demonstrated limit of 0.3 m/s. The TOF sensor combined with a nozzle creates a new device such that the TOF measured with this device provides a measure of the gas flow rate rather than just the gas velocity. More than one nozzle in series is combined to achieve high flow measuring ranges. Compensation for variations in the thermophysical properties of the gas being metered is provided by pulsing the heated wire and measuring sensor outputs when both are immersed in the gas at zero velocity.