Abstract: A method for checking heat exchanger tubes of metallic material includes drying inner surfaces of the heat exchanger tubes. A compressed air-abrasive mixture is then led through the heat exchanger tubes. An eddy-current integrity test of the heat exchanger tubes is then performed.

Abstract: An air flow rate meter in an internal combustion engine which functions on the principle of a constant-temperature anemometer is proposed. The device includes a resistance measurement bridge with a regulatable total bridge current, and the relative orientation between the bridge diagonal voltage and the input voltage of a subsequent amplifier is variable. By means of this variation, an adjustment can be made of the set-point and actual curves of the air flow rate meter. In accordance with a first exemplary embodiment, a supplementary current is supplied to one of the connecting lines of the bridge diagonal and the amplifier; in accordance with a second exemplary embodiment, a voltage divider is located between the bridge diagonal points, and one of the voltage divider resistors is connected parallel to an amplifier having a specific offset voltage.

Abstract: To permit evaluation of only slowly changing low amplitude undulating signals, derived for example from a wheel-speed transducer of a brake anti-block system, and to obtain essentially square-wave output voltage signals having a 1:1 pulse to pulse gap ratio for further signal processing, a temperature stable threshold switch is provided by connecting transistors forming a difference amplifier and purposely mismatched to the input, the mismatch of the transistors defining the threshold level, and being obtained by mismatch in the output circuit thereof, preferably and for example by using pnp lateral transistors having multiple collectors in which the ratio of length of the partial collectors is other than 1:1, and connected, preferably, to a current mirror which has its output connected to the partial collector of the other of the pnp lateral transistors.

Abstract: The current flowing through a reference resistor constitutes the temperature independent output voltage. This current consists of the sum of a first and second current. The first current is a current which is proportional to absolute temperature and has an amplitude which depends on the value of the first resistor. The second current is proportional to the base-emitter voltage of a transistor and its amplitude depends on the value of the second resistor. The values of the first and second resistor are fixed so that the temperature coefficient of the current flowing through the reference resistor is zero. Specifically, one end of the reference resistor is connected to one side of the operating voltage source while the other side is connected through a series circuit including the emitter-collector circuit of the first transistor and the first resistor to ground potential. A second circuit is connected in parallel with the first circuit.

Abstract: An installation for the operation of electromagnetic loads, especially solenoid valves, in fuel supply systems in internal combustion engines, wherein a measuring resistor as well as a switch are connected in series with the load and the entire arrangement is connected to the two supply voltage terminals. The installation comprises two comparators connected in parallel with the measuring resistor, at least one resistor being connected in front of these comparators, and controllable current source arranged between the junction of the threshold switch and the resistor in the proximity of the load, as well as a supply voltage terminal. The supply voltage of one of the comparators is made dependent on the voltage in the freewheel circuit, to maintain at least one of the comparators in the operating position even during freewheeling operation.

Abstract: A method is proposed for operating an electromagnetic load device with a movable armature, especially an injection valve of an internal combustion engine. The load device is supplied, at the beginning of trigger pulse, with a high amperage current and, at least toward the end of the pulse, with a reduced current. This method is characterized in that, starting with a certain amperage, at which preferably the armature is set into motion but has not as yet reached its final position, the current rise is at least reduced. The apparatus aspect comprises a measuring element and switching element connected in series with the load device. A threshold switch is associated with the measuring element to control the switching element. The switching thresholds of the threshold switch can be controlled in dependence on current and/or on time. The first current threshold is at a value at which the armature of the load is preferably being moved, but has not yet reached its final position.

Abstract: A fuel mixture control apparatus for an electronic fuel injection system for internal combustion engines. In a warm-up controller, the fuel injection control pulses are lengthened for enrichment of the fuel-air mixture during engine warm-up on the basis of signals supplied by a temperature transducer. In order to make the warm-up enrichment dependent on prevailing engine states, for example on the conditions of idling and partial or full load, circuitry is provided to sense these conditions and to suitably alter the enrichment factor. A further circuit suppresses the dependence or enrichment on engine status during engine starting. Various embodiments are presented.

Abstract: A frequency divider circuit and variants thereof, intended for use with the fuel injection system of an internal combustion engine. The primary trigger signal is one derived from a rotating engine member and this signal is used to generate two input pulse trains of opposite relative phase. A basic dividing block includes two bistable multivibrators formed by gates with crossed feedback. The inputs to these multivibrators are provided by two-input gates and the input pulse trains are applied, respectively, to the input gates ahead of the first and second multivibrators. The second inputs of the input gates receive the direct or crossed-over outputs of the multivibrators. Additional circuitry is disclosed for providing odd dividing ratios, e.g. 1:3.

Abstract: A controlled main switch, typically a semiconductor switch, is connected in parallel to the load. In accordance with the invention, an auxiliary switch, typically also a semiconductor switch such as a switching transistor is directly connected across the terminals of the load, and with an impedance, for example a resistance, diode, or Zener diode to the main switch, and controlled to switch in synchronism with the main switch, so that the residual voltage across the load due to inherent voltage drop across the terminals of the switch becomes a minimum. Integrated technology may be used, combining preamplifiers and distribution networks in one monolithic chip.

Abstract: A main semiconductor element is placed on a circuit chip; additionally, a compensating semiconductor element is placed thereon, the compensating semiconductor element being a diode, a substrate diode, a Schottky diode, a transistor with shortcircuited base emitter junction, open base transistor, or a resistor, the additional semiconductor element having one terminal connected to the main semiconductor and the other terminal either to the substrate or to a source of potential at least as large as the potential of the main element. The leakage current to be bypassed may affect the main element directly, particularly when the main element is operated in digital on-off mode, or indirectly by passing a compensating current which affects another element such as an operational amplifier, or provides directly for additional current compensating for leakage current of the main element.

Abstract: A controlled main switch, typically a semiconductor switch, is connected in parallel to the load. In accordance with the invention, an auxiliary switch, typically also a semiconductor switch such as a switching transistor is directly connected across the terminals of the load, and with an impedance, for example a resistance, diode, or Zener diode to the main switch, and controlled to switch in synchronism with the main switch, so that the residual voltage across the load due to inherent voltage drop across the terminals of the switch becomes a minimum. Integrated technology may be used, combining preamplifiers and distribution networks in one monolithic chip.

Abstract: A voltage regulator of the type suitable for production as a monolithic integrated circuit for use with a separate reference voltage source is composed of a differential amplifier having a so-called current mirror circuit coupling its outputs, followed by a current amplifying circuit from the output of which a feedback voltage obtained from a resistive divider is brought back to one input of the differential amplifier, the other input thereof being for connection to the reference voltage source. Stabilization of the regulator is obtained by connecting a small capacitance, of a magnitude suitable for provision as an element of a monolithic integrated circuit, between one of the poles of the supply voltage and the point of connection between the differential amplifier and the current amplifier circuit. The differential amplifier has a current source between common emitter connection and ground.