Circuit for detecting a physical quantity

• US 3,922,597 A
• Filed: 10/29/1973
• Issued: 11/25/1975
• Est. Priority Date: 10/31/1972
• Status: Expired due to Term

• Current Assignee: Hiroshi Nagase
• Original Assignee: Hiroshi Nagase
• Inventors: Nagase, Hiroshi
• Primary Examiner(s): Pellinen, A. D.
• Application Number:
  US05/410,499
• Time in Patent Office: 757 Days
• Field of Search: 73/88R,89,362AR 323/74,75B,75N
• US Class Current: 323/367
• CPC Class Codes: G01L 1/2281 for temperature variations

Abstract

A circuit for detecting a physical quantity which comprises a bridge circuit including four sensitive elements having a resistivity which is variable in proportion to a physical quantity to be applied thereto. A power supply is connected to two input terminals of the bridge circuit for applying a voltage thereacross, and a variable resistor comprising a resistor having a predetermined resistance and an adjustable tap is provided for nulling the bridge. The circuit is arranged such that the zero adjustment of the output voltage may be accomplished by adjusting the resistance value of the variable resistor without affecting the characteristics of the thermal zero shift of the bridge circuit to thereby accurately obtain the output voltage corresponding to the physical quantity applied.

Claims

1. A circuit for detecting a physical quantity which may be adjusted without affecting thermal zero shift characteristics, comprising:

a bridge circuit including four sensitive elements coupled in four respective arms thereof, two input and two output terminals, and sensitive elements each having a resistivity which is variable in proportion to a physical quantity to be applied thereto;

variable resistor means including a first fixed resistor having an adjustable tap connected thereto for providing a variable resistance output, whereby adjustment of said tap does not change the thermal characteristics of said first fixed resistor;

second and third resistors connected in series and coupled in parallel with a first arm of said bridge circuit, fourth and fifth resistors connected in series and coupled in parallel with a second arm of said bridge circuit, said first and second arms being adjacent arms of said bridge circuit, said first fixed resistor coupled to a connecting point between said second and third resistors and to a connecting point between said fourth and fifth resistors whereby said first fixed resistor is coupled in parallel with said third and fourth resistors.

2. A circuit as in claim 1, further comprising:

a differential amplifier having two input terminals, one of said input terminals coupled to said adjustable tap and the other input terminal coupled to an output terminal of said bridge circuit; and

, a feedback resistor having a predetermined resistance coupled to said differential amplifier.

3. A circuit for detecting a physical quantity according to claim 2, wherein resistance values of said sensitive elements, said second, third, fourth and fifth resistors, said first fixed resistor means, said resistor means and said feedback resistor are approximately 1K Omega , 9K Omega , 1K Omega , 9K Omega , 10K Omega and 10K Omega respectively.

4. A circuit for detecting a physical quantity according to claim 1, wherein the resistance values of said sensitive elements, said second, third, fourth and fifth resistors and said first fixed resistor are approximately 1K Omega , 9K Omega , 1K Omega , 1 K Omega , 9K Omega and 2K Omega , respectively.