Pressure compensated circuit for ion mass airflow sensors
AssigneeThe Bendix Corporation
InventorBinneg Y. Lao
Life of this patent
Estimating the term…
Abstract
An improved detection circuit for an ion mass air flow sensor having a feedback circuit from the differential output of the sensor to the regulatory input of the high voltage supply. The feedback signal provides a second order correction to the output voltage of the high voltage power supply. This second order correction of high voltage power supply output voltage compensates the differential output of the sensor as a function of the airflow's pressure.
Claims32
A pressure compensated detection circuit for an ion mass flow sensor having at least one corona electrode generating ions by corona discharge and at least one ion collector electrode collecting the generated ions to produce at least two collected ion currents, said circuit comprising:
- first means for generating a mass flow rate signal in response to the collected ion currents;
- second means for generating a total ion current signal indicative of the total number of ions generated in response to said collected ion currents;
- third means for generating a pressure compensation signal in response to said mass flow rate signal;
- fourth means for summing said pressure compensation signal with said total ion current signal and a reference signal to generate a control signal;
- and
- high voltage generator means for generating a high voltage signal applied to the sensor's corona electrode in response to said control signal, said high voltage signal having a value keeping the relationship of the total ion current to said pressure compensation signal and said reference signal a constant.
A pressure compensated detection circuit for an ion mass flow sensor having at least one corona electrode generating ions by corona discharge and a resistive ion collector for collecting the generated ions and producing ion currents at its opposite ends comprising:
- differential amplifier means for generating a mass flow rate signal in response to the difference in the ion currents generated at the opposite ends of the resistive ion collector;
- sum amplifier means for summing the ion currents produced at the opposite ends of the resistive ion collector to generate a total ion current signal;
- means for generating a pressure compensation signal having a value proportional to said mass flow rate signal;
- means for summing said pressure compensation signal with said total ion current signal and a reference signal to generate a control signal;
- high voltage generator means for generating a high voltage signal applied to the at least one corona electrode in response to said control signal, said high voltage signal having a value maintaining the relationship of said total ion current to said pressure compensation signal and said reference signal a constant;
- and
- signal divider means for dividing said high voltage signal to generate said reference signal.
A pressure compensated detection circuit for an ion mass flow sensor having a centrally disposed corona electrode generating ions by corona discharge, a first and second ion collector symmetrically disposed one on each side of the corona electrode along a path parallel to the mass flow, said first and second ion collectors collecting the generated ions to produce a first and second ion current respectively, characterized by:
- a differential amplifier means for generating a mass flow rate signal in response to the difference between said first and second ion currents;
- sum amplifier means for summing said first and second ion currents to generate a total ion current signal;
- means for generating a pressure compensation signal having a value proportional to said mass flow rate signal;
- means for summing said pressure compensation signal with said total ion current signal and a reference signal to generate a control signal;
- and
- high voltage generator means for generating a high voltage applied to said corona electrode in response to said control signal, said high voltage having a value keeping the relations of the total ion current to said pressure compensation signal and said reference signal a constant.
A method for pressure compensating the output of an ion mass flow rate sensor having at least one corona electrode producing ions by corona discharge and at least one ion collector collecting the generated ions to produce at least two ion currents, comprising the steps of:
- amplifying the difference between said two ion currents to generate a mass flow rate signal;
- amplifying the sum of said two ion currents to generate a total ion current signal;
- generating a reference signal;
- correcting said reference signal as a function of said mass flow rate signal to generate a pressure compensated reference signal;
- and
- summing said pressure compensated reference signal with said total ion input current signal to generate a control signal
- controlling a high voltage generator with said control signal to generate a high voltage signal applied to the corona electrode, said high voltage signal activating said corona electrode to generate a corona discharge generating ions at a rate maintaining the relationship of the total ion current to the pressure compensated reference signal a constant.
Dependencies are inferred from the claim text.