Abstract: A fuel gauge is so designed that a fuel level signal having a signal value responsive to the fuel amount in a fuel tank is averaged over time intervals which vary according to whether the liquid level of the fuel in the tank is stable or unstable and a fuel quantity is calculated and displayed according to the averaged value. The stable or unstable condition of the fuel level is discriminated in accordance with vehicle speed, the "on" or "off" position of an ignition switch or the like. Accordingly, when the fuel level is unstable, the signal value is averaged over a time interval which is longer than that used when the fuel level is stable so that the response of display to variation of the fuel level is improved.

Abstract: A vortex shedding device for use in measuring air flow rate into an internal combustion engine includes a duct provided therein with an element for forming vortices in air flowing through the duct. A pair of hot wires is located in the duct which are alternately exposed to vortices generated by the vortex forming element. The hot wires are associated with an electric circuit which detects variations in the resistances of the hot wires and determines the frequency at which vortices are generated in air flowing past the vortex forming element. The electric circuit contains a vortex detector for each of the hot wires so that even if one of the hot wires is broken, a pulse signal is still provided during steady operation of the engine.

Abstract: A Karman vortex detecting type fluid flow rate measuring apparatus which comprises a vortex generator in a conduit, two spaced terminal rod members fixed to the conduit and having respective straight sections which extend along the conduit; a vortex detector supported by the terminal rod members by having both ends thereof soldered or welded to the straight sections of the terminal rod members, respectively, two connecting wires connecting the detector with the corresponding terminal rod members, and means for resiliently holding the straight sections of the terminal rod members, the ends of the detector and the connecting wires relative to the conduit.

Abstract: A Karman vortex type flow measuring apparatus comprises a duct (1) for a fluid whose flow rate or flow velocity is to be measured, and a columnar vortex shedding member (2) extending within the duct transversely of the fluid flow direction. The fluid flow near the vortex shedding member has a width (X) of which the ratio (X/D) to the width (D) of the vortex shedding member lies within the range between 3 and 4. A highly accurate measurement can be achieved independently of the cross-sectional configuration of the duct and for a wide range of the fluid flow rate or flow velocity.

Abstract: A vibration sensor for an automotive vehicle having a multi-peak vibration characteristic of wider responsiveness and of a higher S/N ratio. The vibration sensor comprises a plurality of piezoelectric vibrators so arranged that the piezoelectric voltage signals from the vibrators are synthesized in reverse polarity between two elements having two adjacent resonant frequencies, when the element are deformed in the same direction. Therefore, the voltages are synthesized in the same polarity, when engine knocking frequency lies between two adjacent sensor resonant frequencies, because a vibrator is 180 degrees out of phase with another adjacent vibrator.

Abstract: A Karman vortex type flow measuring apparatus comprises a conduit (2) for a fluid whose flow rate or flow velocity is to be measured, and a columnar vortex shedding member (3) extending within the conduit transversely of the fluid flow direction. Frequency of the vortex shedding is detected by a detector (6) whose output electrical signal is compared by a comparator (20) with a slice level signal, to generate a pulse train which is synchronous with the vortex shedding frequency. The slide level is variable in response to fluctuation in the output electrical signal of the detector (6). A highly accurate measurement can be achieved even when the vortex shedding is unstable.

Abstract: The flow rate is determined from the heat transferred from an electrically heated wire stretched in a fluid flow to the fluid. The wire is placed not on a plane normal to the flow but within a section of the fluid passage bounded by two spaced planes normal to the flow. Preferably the wire is composed of series of line segments which are distributed evenly not only around the central axis of the passage but also in the direction of the flow so that the heat release from the wire in its entirety corresponds to the mean value of fluid velocities at various points.

Abstract: Two metal rods about which a hot wire is wound are projected into a slot of a vortex generating body in which slot alternating fluid flow caused by shedding of vortexes occurs. One end of the hot wire is connected to one of the metal rods and the other end of the hot wire is connected to the other metal rod to enable the metal rods to act as terminal elements.

Abstract: Apparatus for measuring the velocity of the rate of flow of a flowing fluid, comprising a vortex-generating element disposed in a flow tube to create a Karman vortex street in the fluid flow, a hot wire element disposed in the flow tube, transducer means for producing first flow rate signal based on the frequency of shedding of Karman vortices from the vortex-generating element and second flow rate signal based on the cooling effect of the flowing fluid on the hot wire element and signal selection means for selectively putting out the first signal under steady flow conditions and the second signal under pulsating flow conditions. Preferably the hot wire element is made to serve also as the probe element for detection of the vortex generation frequency, and the first signal under steady flow conditions is utilized also to calibrate the second signal.

Abstract: A gas density detecting device for use in an internal combustion engine is disclosed. The device comprises a bellows having a selected gas sealed therein, a guide mechanism provided in the bellows for guiding an expansion motion thereof, a detecting portion provided in the bellows for converting the expansion motion of the bellows into a corresponding electrical output signal, and a correcting resistor provided externally outside of the bellows for correcting the converting factor of the detecting portion.

Abstract: A mass flow sensor comprising a Karman flow detector in a fluid passage including a vortex generator and a vortex detector for detecting periods of generated vortices, and an air density detector including a reference pressure chamber enclosing a standard gas and a comparison pressure chamber into which a fluid in the passage is introduced and detecting means whose output varies proportionally to pressures and temperatures of the fluid introduced in the comparison pressure chamber, thereby compensating a volume flow obtained from the flow detector to obtain a mass flow dependent upon a density of the fluid with high accuracy.

Abstract: An intake air flow rate detector of an internal engine using a Karman vortex sensor, wherein the mass flow rate is obtained by detecting a volumetric flow rate by the Karman vortex sensor and a dynamic pressure or differential pressure at upstream and downstream of the sensor by a strain gage mounted on a partition in a closed chamber. Density compensation of the flow of air is effected only taking said measurement values at a standard range in which the Karman vortex is stable and the differential pressure has a large value.

Abstract: A fluid measuring device comprises flow meter for measuring quantities of flow or flow rates of fluid and flow rectifiers arranged upstream and downstream of the flow meter, whose rectifier elements or cells are sized and positioned such that a ratio W.sub.1 /D of a smaller width W.sub.1 of the cells to an inner diameter D of a passage for the fluid is less than 0.2 and a ratio L/W.sub.1 of a distance L between the flow meter and the upstream flow rectifier to the smaller width W.sub.1 of the cell is within 5.ltoreq.L/W.sub.1 .ltoreq.25, thereby improving an accuracy of measurement without increasing losses of pressure.

Abstract: A rotatable disk having a plurality of calibration segments and at least one marker along the peripheral portion thereof is provided while a stationary pick-up provided adjacent the disk for generating a first signal indicative of calibration segments and a second signal indicative of a reference position of the rotation of the disk. The frequency of the first signal is increased in order to accurately measure the rotational angle from the reference position.

Abstract: A slot of a vortex generating body in which alternating fluid flow occurs in response to shedding of vortexes from the body is narrowed at the middle section thereof where a fluid flow sensing element such as a hot wire is located.

Abstract: A cylindrical vortex generator of a Karman shedding flow meter is set in an inlet tube of an air cleaner of a combustion engine. An air flow uniforming device such as a wire netting is disposed in the inlet tube at a position upstream of the vortex generator for producing in the inlet tube a turbulent but considerably uniformed air flow directed toward the vortex generator. A bypass means is arranged in the inlet tube to make a bypass flow of air directed toward the vortex generator when the combustion engine is under high speed operation.

Abstract: A sensor comprises a layer of an oxygen ion conductive solid electrolyte such as stabilized zirconia, two electrode layers of a catalytic metal such as platinum formed porously on both sides of the electrolyte, only one of them formed on first side of the electrolyte layer being directly exposable to an exhaust gas stream, and a gas passage arranged to allow the exhaust gas to contact the other side of the electrolyte layer with a time lag behind the contact of the gas stream with the first side. A fluctuation in the air/fuel ratio of an air-fuel mixture fed to the engine across the stoichiometric ratio can be detected by this sensor since the fluctuation and the aforementioned time lag cause a difference between oxygen partial pressure on one side of the electrolyte layer and that on the other side, resulting in development of an output voltage of the sensor.

Abstract: A semi-cylindrical body member with a flat section is disposed in a fluid flow conduit in an arrangement to allow the surface of the flat portion to face upstream. Means for counting the number of Karman vortexes created by the body member under flowing of the fluid is disposed in the body member.

Abstract: A solid electrolyte tube closed at one end and two porous electrode layers respectively coated on the outer and inner surfaces of the electrolyte tube constitute a known oxygen concentration cell. A tubular metal shell encloses the electrolyte tube partly such that a closed end portion of the tube protrudes from the shell and that the outer electrode coating is locally in contact with the inside of the shell. To protect the open end of the electrolyte tube against splashing of water during use without interrupting the admission of atmospheric air as a reference gas into the inside of the electrolyte tube, a tubular cap member of a metal is coaxially fixed to and electrically connected at its one end to the shell at one end portion surrounding the open end of the electrolyte tube, and a cross-sectionally circular plug of an insulating material is coaxially and tightly received in and fixed to the cap member to occupy an end portion, contiguous to the free end, of the interior of the cap member.

Abstract: A sensor comprising a plate of an oxygen ion conductive solid electrolyte such as stabilized zirconia, two porous electrode layers of a catalytic metal such as platinum formed on both sides of the electrolyte plate, and two porous ceramic coatings formed respectively on the two electrode layers, wherein both sides of the electrolyte plate are exposable to a gas subject to measurement through the electrode layer and the coating formed on each of them, but the total resistance offered by one of the electrode layers and the coating thereon to the permeation of the gas therethrough is different from that offered by the other electrode layer and coating, so that the gas contacts one side of the electrolyte plate with a time lag behind the contact of the gas with the other side of the plate.