Apparatus and method for isolating noise from a signal

• US 20060284667A1
• Filed: 06/20/2005
• Published: 12/21/2006
• Est. Priority Date: 06/20/2005
• Status: Active Grant

• Current Assignee: SPX Corporation
• Original Assignee: SPX Corporation
• Inventors: Lu, Qixiang
• Granted Patent: US 7,498,806 B2
• Time in Patent Office: Days
• US Class Current: 327/379
• CPC Class Codes: H03K 5/249 using clock signals
• CPC Class Codes: H03M 1/08 of noise H03M1/0617 takes precedence
• CPC Class Codes: H03M 1/12 Analogue/digital converters H03M1/001 – H03M1/10 take precedence

Abstract

A circuit is provided for isolating noise from an input signal to an Analog/Digital (A/D) converter. The circuit includes a plurality of multiplexers and a capacitor connected between the poles of two Single-Pole Multi-Throw (SPMT) multiplexers. A method is also provided for isolating noise from an input signal to the A/D converter using the circuit. The method includes storing a charge in the capacitor and discharging the charge to an A/D converter used to control a system or device.

Claims

1. A circuit, comprising:

a first multiplexer and a second multiplexer;

a capacitor operably connected to a pole of the first multiplexer and a pole of the second multiplexer;

a sensor having a first sensor lead and a second sensor lead, wherein the first sensor lead is operably connected to a first channel of the first multiplexer and the second sensor lead is operably connected to a first channel of the second multiplexer; and

an Analog/Digital (A/D) converter having a first converter lead and a second converter lead, wherein the first converter lead is operably connected to a second channel of the first multiplexer and the second converter lead is operably connected to a second channel of the second multiplexer.

2. The circuit of claim 1, wherein the first multiplexer comprises a Single-Pole Multi-Throw (SPMT) multiplexer and wherein the SPMT comprises at least 2 throws.

3. The circuit of claim 1, wherein the circuit is configured to be incorporated in an automotive air conditioner refrigerant recovery and recharge system.

4. The circuit of claim 1, wherein the first multiplexer and the second multiplexer are substantially identical.

5. The circuit of claim 1, wherein the sensor comprises at least one of a strain gauge or a thermocouple.

6. The circuit of claim 1, wherein the sensor comprises a low voltage transducer.

7. The circuit of claim 1, wherein the first multiplexer comprises at least 4 channels.

8. A method of isolating noise from an input signal to an Analog/Digital (A/D) converter, the method comprising:

generating a first electrical signal in a first sensor lead and a second sensor lead of a first sensor by sensing a condition;

transmitting the first electrical signal from the first sensor lead to a first channel of a first multiplexer and from the second sensor lead to a first channel of a second multiplexer;

using the first electrical signal to store a charge in a capacitor that is operably connected to a pole of the first multiplexer and a pole of the second multiplexer; and

discharging the charge in the capacitor to an A/D converter through a first converter lead that is operably connected to a second channel of the first multiplexer and a second converter lead that is operably connected to a second channel of the second multiplexer.

9. The method of claim 8, wherein the generating step comprises utilizing a strain gauge as the first sensor.

10. The method of claim 8, wherein the generating step comprises utilizing a low voltage transducer as the first sensor.

11. The method of claim 8, further comprising:

converting the charge to a control signal in the A/D converter; and

using the control signal to control an automotive air conditioner refrigerant recovery and recharge system.

12. The method of claim 8, further comprising:

generating a second electrical signal in a third sensor lead and a fourth sensor lead of a second sensor by sensing a condition; and

transmitting the second electrical signal from the third sensor lead to a third channel of the first multiplexer and from the fourth sensor lead to a third channel of the second multiplexer

13. The method of claim 8, wherein the generating step comprises providing an excitation force of at least 5 volts to the first sensor.

14. A circuit, comprising:

first generating means for generating a first electrical signal by sensing a first condition;

first transmitting means for transmitting the first electrical signal from the first generating means to a first channel of a first multiplexer and to a first channel of a second multiplexer;

storing means for storing a charge using the first electrical signal, wherein the storing means is operably connected to a pole of the first multiplexer and a pole of the second multiplexer; and

discharging means for discharging the charge in the storing means to an A/D converter through a first converter lead that is operably connected to a second channel of the first multiplexer and a second converter lead that is operably connected to a second channel of the second multiplexer.

15. The circuit of claim 14, wherein the first generating means comprises a strain gauge.

16. The circuit of claim 14, wherein the first generating means comprises a low voltage transducer.

17. The circuit of claim 14, further comprising:

converting means for converting the charge to a control signal in the A/D converter; and

controlling means for using the control signal to control an automotive air conditioner refrigerant recovery and recharge system.

18. The circuit of claim 14, further comprising:

second generating means for generating a second electrical signal by sensing a condition; and

second transmitting means for transmitting the second electrical signal to a third channel of the first multiplexer and to a third channel of the second multiplexer.

19. A circuit, comprising:

a first Single-Pole Multi-Throw (SPMT) multiplexer including a first throw and a second throw;

a second SPMT multiplexer including a third throw and a fourth throw;

a capacitor operably connected to a pole of the first multiplexer and a pole of the second multiplexer;

a sensor having a first sensor lead and a second sensor lead, wherein the first sensor lead is operably connected to a first channel of the first multiplexer and the second sensor lead is operably connected to a first channel of the second multiplexer; and

an Analog/Digital (A/D) converter having a first converter lead and a second converter lead, wherein the first converter lead is operably connected to a second channel of the first multiplexer and the second converter lead is operably connected to a second channel of the second multiplexer.

20. The circuit of claim 19, wherein the sensor comprises at least one of a strain gauge, a thermocouple or a low voltage transducer.