Abstract: The temperature range for stable operation of a flueric partial pressure sensor (300) is improved by temperature-responsive means (80, 60) which vary with temperature change the suction applied by a flueric aspirator (27) in drawing gas through sensor bridge legs (12, 13) and a power line (37) of a flueric amplifier (11). The temperature-responsive means may comprise temperature-sensitive adjustment means (107, FIG. 2) embodied in a pressure reducing valve (80) to vary the pressure of working gas supplied by way of delivery line (28) for driving the flueric aspirator. Alternatively or additionally the temperature-responsive means may comprise a temperature-sensitive bleed valve (60) incorporated in a common outlet (14) from the bridge legs and the flueric amplifier power line.

Abstract: Signal output means (11) responsive to gas flow and particularly suited for use in gas flow indicator apparatus (10), has first and second pressure-datum valves (24, 25) arranged in downstream order in a gas conduit (16), the second pressure-datum valve (25) being arranged to open at a lower pressure difference than the first pressure-datum valve (24). A flueric amplifier (15) has a power jet port (28) connected to the gas conduit (16) on the upstream side of the first pressure-datum valve (24), opposed control pressure ports (26, 27) connected respectively to a chamber (22) formed between the first and second pressure-datum valves (24, 25) and to the gas conduit (16) downstream of the second pressure-datum valve (25), and a vent port (30) also connected to the gas conduit (16) downstream of the second pressure-datum valve (25). A pressure signal output by the flueric amplifier (15) in response to gas flow through the conduit (16) may be used to trigger a visual or audio warning device (14).

Abstract: A flueric partial pressure sensor includes a flueric bridge having two bridge legs adapted for sensing a reference-gas and sample-gas mixture. A linear resistor and an orifice resistor are incorporated in each of the bridge legs which are conjoined to discharge from a single outlet. The resistors are arranged to provide an asymmetric balance of the flow rates through the bridge legs. The asymmetric balance is selected so that in operation a constant pressure output signal is generated for a chosen partial pressure of a constituent gas of the sample-gas mixture in varying absolute pressure conditions such as changes in altitude. Respective pressure signal outlets connected one with each bridge leg at a position between the linear resistor and the orifice resistor are used to effect control of a flueric laminar flow proportional amplifier. Outputs from the flueric amplifier may be used to regulate a fluid mixing valve shown in FIG. 3, or to effect switching of an indicator device shown in FIG. 4.

Abstract: The invention provides a breathable gas regulator of the demand type for use with a low supply pressure (10 p.s.i or less) gas source.The regulator requires no greater demand effort on the part of a user than is required with present-day regulators of the same type which operate with much higher pressure (70 p.s.i. and above) gas sources, and it requires ducts, diaphragms and valves of no greater size than are required by present-day regulators. This is achieved by inclusion of a servo valve that is actuated by a fluidic amplifier arrangement responsive to the user's breathing pressure.In an embodiment of the invention particularly suited for use by an aviator, the regulator includes a pneumatically operated mixing valve arrangement for automatically varying, according to altitude, the proportions of, say, oxygen and air supplied to the demand valve of the regulator, and the mixing valve arrangement includes a fluidic gas concentration sensor.