Abstract: A differential pressure monitoring device utilizing two crystalline frequency sensors exposed to different pressures for generating two signals which are combined by a frequency mixer. Two offset based frequency crystal sensors are each exposed to different pressures and the resulting frequencies are mixed to measure the pressure differential between the two crystals. When the crystals are exposed to a common pressure, the crystals have an offset based frequency response that is consistent with pressure. When the two crystals are exposed to pressures, the offset frequencies are mixed together to create a differential frequency that is precisely related to the differential in the pressures placed on the two different crystal sensors.

Abstract: A flow conditioning plate for interposition in a flow line has a pattern of apertures which introduces a flow irregularity characteristic of a commonly encountered irregular flow in a plant, such as the disturbance introduced by one or more junctions or fittings in the upstream flow path. The apertures may introduce a specific flow distribution, asymmetry of flow profile or swirl component, and these may be tuned to simulate a plant condition that occurs downstream of one or more bends, elbows or T junctions. The disturbance persists, or evolves in a known way for a well defined distance along the flow path to simulate field flow conditions, and a flow meter is tested or calibrated in the disturbed segment, preferably at a defined position, under known flow to produce a calibration table. The meter may then be later installed to measure the irregular flow in an unconditioned flow line at a plant.

Abstract: Disclosed is an air tube for use in a spirometer. This air tube is disposable and is at least partially, preferably completely, biodegradable, so that is can be economically produced and discarded after use by a single spirometer user. Cross-patient contamination and expensive sterilization procedures are thus avoided. In addition, making this air tube biodegradable allows for the use of plentiful and inexpensive materials of construction, such as cardboard, paper, biodegradable polymers and the like, and reduces the environmental burden caused by disposing of this component.