Methods and devices for measuring instantaneously a mean pressure in a fluid medium

Claim 3

Apparatus for measuring a means pressure in a fluid medium in synchronism with the rotation of an internal combustion engine, comprising: means for measuring instantaneous pressures in said fluid medium and converting said measured pressures into an analog electrical signal; means for generating pulse signals at a rate which is synchronized with the rotation of said engine; means for sampling said analog signal, including a gate circuit having one input coupled to the analog signal output of said measuring means and a second input coupled to the output of said synchronized pulse rate generator; integrating means, including an integrating capacitor, coupled to the output of said sampling means for integrating said sampled signals; means coupled to the output of said integrating means for converting the amplitude of said sampled signals into a time value, including a clock pulse generator and counter means for counting clock pulses generated by said clock pulse generator during a predetermined constant-current discharge time period of said integrating capacitor; means coupled to said counter means for totalizing the clock pulses counted for a sampled signal during a predetermined portion of the rotational period of said engine; and means for resetting said integrating means, including a comparator circuit coupled to said integrating means for comparing the output signal from said integrating means with a reference voltage and for generating a comparison signal when said integrating and reference signals are equal, and switch means connected across said integrating capacitor and connected to the output of said comparator means, said switch being closed by said comparison signal to reset said integrating means.

Claim 4

Apparatus for measuring a means pressure in a fluid medium in synchronism with the rotation of an internal combustion engine, comprising: means for measuring instantaneous pressures in said fluid medium and converting said measured pressures into an analog electrical signal; means for generating pulse signals at a rate which is synchronized with the rotation of said engine; means for sampling said analog signal, including a gate circuit having one input coupled to the analog signal output of said measuring means and a second input coupled to the output of said synchronized pulse rate generator; integrating means, including an integrating capacitor, coupled to the output of said sampling means for integrating said sampled signals; means coupled to the output of said integrating means for converting the amplitude of said sampled signals into a time value, including a clock pulse generator and counter means for counting clock pulses generated by said clock pulse generator during a predetermined constant-current discharge time period of said integrating capacitor; means coupled to said counter means for totalizing the clock pulses counted for a sampled signal during a predetermined portion of the rotational period of said engine; and means for resetting said integrating means, including a comparator circuit coupled to said integrating means for comparing the output signal from said integrating means with a reference voltage and for generating a comparison signal when said integrating and reference signals are equal, and switch means connected across said integrating capacitor and connected to the output of said comparator means, said switch being closed by said comparison signal to reset said integrating means.

Claim 5

The apparatus according to claim 2, wherein said pressure measuring means comprises a pressure pick-up and a high-input low-output impedance amplifier circuit having its input coupled to the output of said pick-up and its output coupled to the input of said sampling means.

Claim 6

The apparatus according to claim 2, wherein said sampling means comprises an impedance matching amplifier having an input coupled to an output of said pressure measuring means and an electronic switch member having input and output electrodes coupled to said impedance matching amplifier and to said integrating means, respectively, and a control electrode coupled to said synchronized pulse signal generator.

Claim 7

The apparatus according to claim 2, wherein said integrating means comprises an impedance matching amplifier coupled to the ouput of said impedance matching amplifier, a constant-current generator coupled to the output of said electronic switch member, and an integrating amplifier, to which said integrating capacitor is connected, having an input coupled to said constant-current generator and an output coupled to said comparator circuit.

Claim 8

The apparatus according to claim 2, wherein: said pressure measuring means comprises a pressure pickup and a high-input low-output impedance amplifier circuit having its input coupled to the output of said pickup; said sampling means comprises an impedance matching amplifier having an input coupled to an output of said high-input low-output impedance amplifier of said pressure measUring means, and an electronic switch member having an input electrode coupled to said impedance matching amplifier and a control coupled to said synchronized pulse signal generator; and said integrating means comprises a second impedance matching amplifier coupled to an output electrode of said electronic switch member, a second electronic switch member coupled to the output of said second impedance matching amplifier, a constant-current generator coupled to the output of said second electronic switch member, and an integrating amplifier, to which said integrating capacitor is connected, having an input coupled to said constantcurrent generator and an output coupled to said comparator circuit.