Linearization of a sensing bridge circuit output

• US 5,122,756 A
• Filed: 11/28/1989
• Issued: 06/16/1992
• Est. Priority Date: 11/28/1989
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Nelson, Richard W.
• Primary Examiner(s): Harvey, Jack B.
• Application Number:
  US07/442,205
• Time in Patent Office: 931 Days
• Field of Search: 324/705, 324/706, 324/720, 324/725, 73/204.15, 73/204.11, 73/204.18
• US Class Current: 324/706
• CPC Class Codes: G01F 1/698 Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
• CPC Class Codes: G01P 5/12 using variation of resistance of a heated conductor

Abstract

The output of a condition sensing bridge is linearized by providing a feedback from the output to the bridge supply which feedback is in the linear form of V_B =KV_O +V_X where V_B is the bridge supply voltage, K is a proportionality constant, V_O is the bridge output and V_X is the feedback offset voltage.

Claims

1. A linearization circuit for a mass air flow sensor, comprising:

an upstream thermally sensitive resistor;

a heat source;

a downstream thermally sensitive resistor, said heat source being disposed between said upstream and downstream thermally sensitive resistors;

a first reference resistor connected electrically in series with said upstream resistor between a first circuit point and a ground potential to form a first current path;

a second reference resistor connected electrically in series with said downstream resistor between said first circuit point and said ground potential to form a second current path, said first and second current paths being connected in electrically parallel association;

an amplifier having first and second inputs, said first input being connected in electrical communication with a first junction between said first reference resistor and said upstream thermally sensitive resistor, said second input being connected in electrical communication with a second junction between said second reference resistor and said downstream thermally sensitive resistor, said amplifier having an output;

means for adding an offset voltage to an amplification of a voltage difference between said first and second junctions to provide an amplified and offset signal at said output of said amplifier; and

means for connecting said output of said amplifier in electrical communication with said first circuit point, said output of said amplifier being generally linear.

2. The circuit of claim 1, wherein:

said connecting means comprises an operational amplifier.

3. The circuit of claim 1, wherein:

said connecting means comprises a means for modifying said output of said amplifier and providing said modified output as an input to said first circuit point.