Abstract: A magnetically joinable play tile comprising a tile body having an edge; and a rotatable magnet carried by tile body adjacent to the edge.

Abstract: An infrared motion sensor has a multi element IR detector with first and second separate arrays of optical elements associated with respective first and second detector elements and a partition of a material substantially opaque to IR radiation and substantially transparent to visible/NIR light arranged to separate the IR optical paths from the first and second optical elements to the respective first and second detector elements. In this way, the detector elements function individually with respect to IR radiation and individual optical elements produce separate and independently oriented fields of view on the first and second sides of the sensor, while visible/NIR light still falls on both detector elements so that detector element signals resulting from NIR radiation roughly cancel one another.

Abstract: An infrared motion sensor has a multi element IR detector with first and second separate arrays of optical elements associated with respective first and second detector elements and a partition of a material substantially opaque to IR radiation and substantially transparent to visible/NIR light arranged to separate the IR optical paths from the first and second optical elements to the respective first and second detector elements. In this way, the detector elements function individually with respect to IR radiation and individual optical elements produce separate and independently oriented fields of view on the first and second sides of the sensor, while visible/NIR light still falls on both detector elements so that detector element signals resulting from NIR radiation roughly cancel one another.

Abstract: A pyroelectric detector circuit comprises a pyroelectric sensor element connected to a load resistor and to an input of a buffer amplifier having a feedback path for multiplying the resistance of the load resistor at non-zero frequencies. This feedback enables the use of a smaller load resistor which is multiplied to produce a higher effective load resistance necessary for proper low frequency response of the detector circuit.

Abstract: A circuit is provided for generating a voltage signal corresponding to a wiper position in a linear or circular potentiometer having an open wiper position or an open wiper angle, respectively. The voltage signal circuit includes provisions for determining when a wiper is in an open wiper position or angle region. When the circuit is used with a freely rotating circular potentiometer, the voltage signal may be used to determine wind direction. The circuit includes a voltage source coupled to a conducting element and a wiper. A pulling resistor driven by an operational amplifier is coupled to the wiper and voltage source to provide an identifiable voltage signal corresponding to the open wiper state during rotation through the open wiper angle region.

Abstract: Methods and apparatus for remote calibration of combustible gas detectors in which calibration initiation signals are applied to a sealed, explosion-proof sensor assembly to effect a remote calibration sequence and storage of calibration factors.

Abstract: Methods and apparatus for measuring combustible gases in which an active sensor is maintained at controlled, temperature in respect of a reference sensor by means of a bridge-sampling system and a variable duty cycle system responsive to the bridge sampling system adapted to periodically bypass the current from the active sensor in a reference bridge network.

Abstract: A portable self-calibrating pH meter particularly adapted for use by unskilled operators in adverse environment conditions is disclosed which has a minimum of operator controls while preventing operator errors and while providing effective and accurate pH measurement.

Abstract: An apparatus for measuring electrochemical species in well drilling mud. The apparatus comprises a sulfide electrode, a pH electrode and a reference electrode. An electrical circuit is provided therefore which provides temperature compensation of the electrochemical signals. A method of using said apparatus to determine hydrogen sulfide in well drilling mud is disclosed.

Abstract: Methods and apparatus relating to systems for determination of sulfide species and hydrogen sulfide hazard potential of well drilling mud.