An inlet or primary particle size fractionator for a direct-reading PM.sub.2.5 mass sensor described herein may remove atmospheric particles of a given size, such as particles greater than the inlet cut point (e.g., having a 10 μm AD cut point) and may transport particles less than the cut point to a mass sensing element or a secondary particle size fractionator (e.g., having a 2.5 μm AD cut point). The inlet may have a flow rate range of between 1 mL/min and 50 mL/min (or higher flow rates depending on the application). The inlet may include a virtual impactor (VI), real impactor, cyclone, or virtual cyclone (VC). A sensing element may measure particle mass below the primary particle size fractionator (e.g., 2.5 μm AD particles with a 10 μm AD cut point inlet) and/or between the size range of the primary and secondary particle size fractionators (e.g., between 2.5 μm and 10 μm AD, or coarse particles).

An infant sleep device may include a platform for supporting an infant, a base upon which the platform is supported, and one or more weight sensors positioned to measure weight of an infant positioned on the platform.

An infant sleep device may include a platform for supporting an infant, a base upon which the platform is supported, and one or more weight sensors positioned to measure weight of an infant positioned on the platform.

Weigh-in-motion sensors comprise a beam including a plate with a load-bearing surface, and a tube portion including a base wall and a cover and defining a cavity therebetween. A sensing package is disposed within the cavity and is under pre-load with the cover and the base wall. The sensing package comprises a piezoelectric element. The base wall includes an aperture extending from a mounting surface to the cavity. The aperture includes a fastener therein to secure the sensing package within the cavity. The fastener is sized having a cross-section dimension taken through a center axis of the fastener that is greater than that of a cross-section dimension of the piezoelectric element taken along the fastener center axis. In an example, the fastener has a cross-section dimension sized about 10 percent or greater in dimension than that of the respective cross-section dimension of the piezoelectric element.

Weigh-in-motion sensors comprise a beam including a plate with a load-bearing surface, and a tube portion including a base wall and a cover and defining a cavity therebetween. A sensing package is disposed within the cavity and is under pre-load with the cover and the base wall. The sensing package comprises a piezoelectric element. The base wall includes an aperture extending from a mounting surface to the cavity. The aperture includes a fastener therein to secure the sensing package within the cavity. The fastener is sized having a cross-section dimension taken through a center axis of the fastener that is greater than that of a cross-section dimension of the piezoelectric element taken along the fastener center axis. In an example, the fastener has a cross-section dimension sized about 10 percent or greater in dimension than that of the respective cross-section dimension of the piezoelectric element.

An apparatus includes a platform or other accessory that is supported by one or more piezoelectric transducers. As items are placed on or removed from the accessory, the piezoelectric transducer generates an electric charge that is representative of a change in weight. An amplifier receives the charge and provides output voltage that can be sampled to determine a weight value. In one implementation the platform may be supported by a transducer assembly comprising a frame and a pair of piezoelectric transducers on opposite sides of the frame. Signals from the pair may be used to compensate for environmental effects on the assembly, such as changes in temperature. The piezoelectric transducers and associated circuitry are extremely energy efficient, consuming little electrical power during operation.

An apparatus includes a platform or other accessory that is supported by one or more piezoelectric transducers. As items are placed on or removed from the accessory, the piezoelectric transducer generates an electric charge that is representative of a change in weight. An amplifier receives the charge and provides output voltage that can be sampled to determine a weight value. In one implementation the platform may be supported by a transducer assembly comprising a frame and a pair of piezoelectric transducers on opposite sides of the frame. Signals from the pair may be used to compensate for environmental effects on the assembly, such as changes in temperature. The piezoelectric transducers and associated circuitry are extremely energy efficient, consuming little electrical power during operation.

Apparatus and related methods are provided in a surface acoustic wave (SAW) scale for measuring weight of a load. A processor reads a first frequency of a SAW delay line operating in a first mode. A push oscillator injects a frequency similar to but different than the first frequency in order to cause the SAW delay line to operate in a second mode, and the processor reads a second frequency of the SAW delay line operating in the second mode. A difference between the frequencies is calculated and compared to values in a stored table to determine the first mode at which the SAW delay line was operating. Based on a determination of the first mode and the first frequency, the weight of the load is determined. This determined weight can be used to recalibrate an auxiliary weight sensor.

Apparatus and related methods are provided in a surface acoustic wave (SAW) scale for measuring weight of a load. A processor reads a first frequency of a SAW delay line operating in a first mode. A push oscillator injects a frequency similar to but different than the first frequency in order to cause the SAW delay line to operate in a second mode, and the processor reads a second frequency of the SAW delay line operating in the second mode. A difference between the frequencies is calculated and compared to values in a stored table to determine the first mode at which the SAW delay line was operating. Based on a determination of the first mode and the first frequency, the weight of the load is determined. This determined weight can be used to recalibrate an auxiliary weight sensor.

Surface acoustic wave (SAW) weighing apparatus and related methods are provided for measuring weight of a load employing a displaceable elastic member that is displaced by the load. A piezoelectric SAW transducer is coupled to the elastic member. The piezoelectric transducer along with an amplifier electrically coupled thereto form a delay line oscillator circuit that is configured to generate an oscillating signal in response to displacement of the elastic member by the weight of the load. A magnet is spaced from a Hall effect sensor. The magnet produces a magnetic field, and the Hall effect sensor is configured to measure strength of the magnetic field which is related to displacement of the elastic member and the weight of the load. Circuitry generates frequency data that characterizes frequency of the oscillating signal. The frequency data is related to displacement of the elastic member and the weight of the load.