Abstract: Apparatus for measuring the mass flow of a fluid comprises a first ionizing electrode which, in use, is located in the path of fluid flow and, when energized, ionizes said fluid. A second substantially cylindrical, hollow collector electrode extends around said first electrode so that, in use, the ions produced by the first electrode migrate to the second electrode. The second electrode includes a plurality of conductive rings which are spaced apart in the direction of fluid flow and insulating material is interposed between adjacent rings, but is arranged so as not to be exposed to the ions migrating to the rings in use. Means is responsive to the amount of ion migration to the various conductive rings for measuring the displacement of the ions by the fluid flowing past the electrodes, the displacement being dependent upon the mass flow of the fluid.

Abstract: A corona discharge gas flow transducer includes a high tension discharge electrode, and a receiving electrode having two terminals, the difference between the current flow from these terminals representing the gas mass flow. For deriving a current difference signal there is a circuit comprising a current to voltage converter, switch means alternately connecting the two terminals to the converter, and further switch means a.c. coupled to the converter and operable in synchronism with the switch means.The transducer is used in an i.c. engine fuel system in which the transducer output is integrated over a fixed engine crankshaft angle to generate a fuel demand signal.

Abstract: An i.c. engine fuel injection control includes a corona-discharge type transducer for measuring the mass of air aspirated by the engine. Since such a transducer is humidity sensitive a compensation circuit is provided for automatically applying a humidity correction to the control circuit which is used to control the quantity of fuel injected as a function of the transducer output. This control circuit includes an integrator to which the transducer output is periodically applied and a current source which periodically discharges the integrator, the time taken to discharge determining the quantity of fuel injected. The current source is controlled by the humidity sensitive means, to obtain the required compensation.

Abstract: A pulse producing device has an E-shaped core with an input winding and an output winding, so that flow of flux between the limbs of the core produces an output in the windings. The flow of flux is controlled by parts rotating close to the limbs, and these parts are formed on a rotatable plate the periphery of which is split and deformed to provide two rows of tags, one row passing close to the central limb and one of the outer limbs and the other row passing close to the central limb and the other outer limb.

Abstract: A radiation-sensitive switching circuit has a light emitting diode which supplies light to a photo-transistor, the light being interrupted from time to time. When the photo-transistor is illuminated, current builds up and when this current reaches a predetermined value, a trigger circuit changes state. The peak output of the photo-transistor is measured and the trigger circuit is arranged to change state when the output of the device is a set proportion of the peak output, so as to allow for aging of the components.

Abstract: A radiation-sensitive switching circuit includes a light emitting diode which from time to time illuminates a photo-transistor, the photo-transistor serving when its output reaches a predetermined value to operate a trigger circuit. In order to allow for aging of the components, the current flow through the diode is increased when the output from the transistor falls below a known level. Conveniently, this is achieved by having a transistor in parallel with the diode, and turning the transistor off when the output from the photo-transistor becomes too low.