Temperature-coefficient-generating circuit and temperature-compensating circuit using the same

• US 20030006822A1
• Filed: 09/18/2001
• Published: 01/09/2003
• Est. Priority Date: 03/27/2001
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Murakami, Mitsumasa, Hara, Masaya
• Granted Patent: US 6,853,237 B2
• Time in Patent Office: Days
• US Class Current: 327/513
• CPC Class Codes: G01K 15/00 Testing or calibrating of thermometers

Abstract

The invention provides a temperature-compensating circuit which comprises first degree and second degree temperature-coefficient-generating circuits respectively comprising an operational amplifier and a plurality of resistors each having different temperature coefficient, a sign-inverting circuit, and first degree and second degree temperature-coefficient-adjusting circuits. Resistance values of the resistors of the first degree and second degree temperature-coefficient-generating circuits are decided so that voltage amplification factors are linearly or quadratically changed as a temperature changes. The sign-inverting circuit inverts signs of temperature coefficients generated by the first degree and second degree temperature-coefficient-generating circuits and the first degree and second degree temperature-coefficient-adjusting circuits adjust temperature coefficients generated by the first degree and second degree temperature-coefficient-generating circuits to predetermined values. The temperature-compensating circuit generates any temperature coefficients necessary for temperature compensation to cancel an offset drift constant in the temperature characteristic of a sensor output and fluctuation components due to span-shift first degree and second degree temperature coefficients.

Claims

1. A first degree temperature-coefficient-generating circuit comprising an amplifying circuit which includes a combination of an operational amplifier and a plurality of types of resistors, each resistor having different temperature coefficients,

wherein resistance value of each resistor is decided so that voltage amplification factor of the amplifying circuit is linearly changed with a first degree temperature coefficient as a temperature changes.

2. The first degree temperature-coefficient-generating circuit according to claim 1, wherein the plurality of types of resistors includes two types of resistors.

3. The first degree temperature-coefficient-generating circuit according to claim 1, wherein the plurality of types of resistors includes three types of resistors.

7. An offset-drift-constant temperature-compensating circuit comprising:

the first degree temperature-coefficient-generating circuit of claim 1;

a sign-inverting circuit for receiving a signal voltage from the first degree temperature-coefficient-generating circuit and generating a voltage obtained by inverting the sign of the first degree temperature coefficient in the received signal voltage;

a sign-switching circuit for selecting an output supplied from either of the first degree temperature-coefficient-generating circuit and the sign-inverting circuit; and

a first degree temperature-coefficient-adjusting circuit for receiving a signal voltage from the sign-switching circuit and generating a voltage obtained by adjusting a first degree temperature-coefficient component to a predetermined value in the roceived signal voltage,

wherein a voltage obtained by dividing a power-supply voltage is applied as an input voltage of the first degree temperature-coefficient-generating circuit, and an output voltage to be linearly changed in accordance, with an ambient-temperature change is generated at an output end of the first degree temperature-coefficient-adjusting circuit.

8. A span-shift temperature-coefficient first degree compeiisatiflg circuit comprising:

the first degree temperature-coefficient-generating circuit of claim 1 in which the voltage amplification factor is set to either of 1 and 2 at a reference temperature;

a sign-inverting circuit for receiving a signal voltage from the first degree temperature-coeLficient-generating circuit and generating a voltage obtained by inverting the sign of the first degree temperature coefficient in the received signal voltage;

a sign-switching circuit for selecting an output supplied from either of the first degree temperature-coefficient-generating circuit and the sign-inverting circuit; and

a first degree temperature-coefficient-adjusting circuit for receiving a signal voltage from the sign-switching circuit and outputting a voltage obtained by adjusting the first degree temperature coefficient to a predetermined value in the received signal voltage;

wherein a voltage including a first degree temperature coefficient component is used as an input signal of an operational amplifier of a first degree temperature-coefficient-generating circuit, and

a signal voltage is generated at an output end of the fist degree temperature-coefficient-adjusting circuit, which cancels the first degree temperature coefficient component of the input sianal and includes a second degree temperature coefficient component.

4. A second degree temperature-coefficient-generating circuit comprising an amplifying circuit which includes a combination of an operational amplifier and a plurality of types of resistors, each resistor having different temperature coefficients,

wherein resistance value of each resistor is decided so that voltage amplification factor of the amplifying circuit is quadratically changed with a second degree temperature coefficient as a temperature changes.

5. The second degree temperature-coefficient-generating circuit according to claim 4, wherein the plurality of types of resistors includes two types of resistors.

6. The second degree temperature-coefficient-generating circuit according to claim 4, wherein the plurality of types of resistors includes three types of resistors.

9. A span-shift temperature-coefficient second degree compensating circuit comprising:

the second degree temperature-coefficient-generating circuit of claim 4 in which the voltage amplification factor is set to 1 at a reference temperature; and

a second degree temperature-coefficient-adjusting circuit for receiving a signal voltage from the second degree temperature-coefficient-generating circuit and outputting a voltage obtained by adjusting the second degree temperature coefficient to a predetermined value in the received signal voltage,

wherein the operational amplifier of the second degree temperature-coefficient-generating circuit receives a signal voltage including a second degree temperature coefficient component from the span-shift temperature-coefficient first degree compensating circuit of claim 8, and

an output voltage is generated in which a second degree temperature coefficient component in a fluctuation component of the output signal to a temperature change is canceled and a quaternary temperature coefficient component at an output end of the second degree temperature-coefficient-adjusting circuit is included.