Abstract: A flow rate meter for measuring the flow rate of a fluid medium, especially that of the air aspirated by an internal combustion engine. A hot wire or film is placed in the air stream and is made part of an electrical circuit powered by the output of a differential amplifier. The voltage drop across the resistor is monitored at the input of the differential amplifier where it is compared with fixed or compensated values. In order to reduce the effect that airborne particles, which are deposited on the hot wire or film, have on the measuring characteristics of the apparatus, the wire or film are shaped so that their leading edge constitutes an area much smaller than the surfaces which are substantially parallel to the stream lines.

Abstract: A method and apparatus for determining the proportions of the air-fuel mixture constituents supplied to an internal combustion engine from a mixture preparing device such as a carburator, a fuel injection device or other suitable mixture preparing device. The method according to the invention serves to simplify the processing of output signals that are supplied to a mixture preparing device having at least two .lambda. sensors. The invention is especially suitable for use with large engines with several exhaust conduit systems, such as so-called V-engines, in which generally there is an unequal mixture distribution between the two rows of cylinders. By employing at least two .lambda. sensors in the exhaust gas conduit system for monitoring the exhaust gas composition, one succeeds in determining the mixture composition of the air-fuel mixture applied to all cylinders, and in influencing the air-fuel mixture in a suitable supplementary manner by a feed back of the actual value signals generated by the .lambda.

Abstract: A flow rate meter for measuring the flow rate of a fluid medium, especially that of the air aspirated by an internal combustion engine. A hot wire or film is placed in the air stream and is made part of an electrical circuit powered by the output of a differential amplifier. The voltage drop across the resistor is monitored at the input of the differential amplifier where it is compared with fixed or compensated values. In order to reduce the effect that airborne particles, which are deposited on the hot wire or film, have on the measuring characteristics of the apparatus, the wire or film are shaped so that their leading edge constitutes an area much smaller than the surfaces which are substantially parallel to the stream lines.

Abstract: A flow rate measuring device, especially for measuring the flow rate of incoming fresh air in the induction tube of an internal combustion engine in which a temperature-dependent sensor, e.g. a resistor, is exposed to the air flow while the current through the sensor is controlled and monitored to obtain a signal related to the air flow rate. In order to prevent damage to the sensor from high-temperature flame fronts due to backfiring and also from inadvertent mechanical contact with tools, etc., there is provided at least one protective element downstream of the sensor and possibly another element upstream. The protective element is a plate-like barrier permitting essentially unimpeded air flow. The pattern of the element may be a grid or sieve, a honeycomb pattern or a plurality of parallel tubes.

Abstract: A method and apparatus for detecting when the internal resistance of an oxygen sensor is too high for useful signal processing. A reference voltage is applied to the sensor signal to generate a test voltage which is compared with two different threshold voltages. The three possible magnitude states of the test voltage with respect to the thresholds cause the comparator output signals to define logical conditions which are processed by logical gating circuitry to inhibit a timing circuit which otherwise would switch fuel mixture preparation from sensor-controlled operation to open-loop, direct control after a period of time.

Abstract: Undesired deposits accummulating on the surface of a temperature-varying airflow sensing resistor are burned off periodically by increasing the current through it. To eliminate errors caused by a reversal in the direction of airflow, a temperature independent resistor is placed downstream of the temperature-varying resistor and is maintained at the same operating temperature as the latter.

Abstract: A circuit arrangement for linearizing the output signal of a probe such as a hot-wire probe used for quantitative air measurement in the intake manifold of an internal combustion engine which includes a log stage, a multiplier stage and an antilog stage connected in series, the probe signal being applied to the input of the log stage and the linearized output signal taken from the output of the antilog stage.