Independent-excitation cross-coupled differential-pressure transducer

• US 20020134163A1
• Filed: 03/22/2001
• Published: 09/26/2002
• Est. Priority Date: 03/22/2001
• Status: Active Grant

• Current Assignee: Kavlico Corporation (Sensata Technologies Holding Plc)
• Original Assignee: Kavlico Corporation (Sensata Technologies Holding Plc)
• Inventors: Clifford, Mark J.
• Granted Patent: US 6,581,468 B2
• Time in Patent Office: Days
• US Class Current: 73/715
• CPC Class Codes: G01L 15/00 Devices or apparatus for measuring two or more fluid pressure values simultaneously
• CPC Class Codes: G01L 19/0038 being part of the housing other details about the housing G01L19/14
• CPC Class Codes: G01L 9/045 with electric temperature compensating means non electric temperature compensating means G01L19/04

Abstract

The present invention provides a differential-pressure transducer having two sensors cross-coupled and independently excited. A first Wheatstone Bridge pressure sensor has a first sensitivity and is excited by a first voltage. A second Wheatstone Bridge pressure sensor has a second sensitivity and is independently excited by a second voltage different from said first voltage. The excitation voltages are independently adjusted to increase or decrease the sensitivities of the sensors to substantially match. The outputs of the sensors are cross-coupled to each other to reduce the offset difference errors between the pressure sensors. Sensitive electronics are isolated within the sealed housing to protect them from harsh surrounding media. The transducer is configured to provide either a four pressure differential pressure measurement or a three pressure gauge differential pressure measurement.

Claims

1. A pressure transducer comprising:

a first pressure sensor having a first sensitivity and excited by a first voltage;

a second pressure sensor having a second sensitivity different from the first sensitivity and excited by a second voltage different from said first voltage, and wherein the first and second voltages are independently adjustable to increase or decrease the sensitivities of the first and second sensors to substantially match each other;

and wherein;

the outputs of the sensors are cross-coupled to each other to reduce the offset difference errors between the pressure sensors.

2. The pressure transducer of claim 1, wherein the first and second voltages are adjusted to substantially match the sensitivities of the first and second sensors over a range of pressures and temperatures.

3. The pressure transducer of claim 1, wherein the first and second voltages are independently adjustable to increase the sensitivity of the first sensor and to decrease the sensitivity of the second sensor to substantially match each other.

4. The pressure transducer of claim 1, wherein:

the first and second pressure sensors are Wheatstone Bridge pressure sensors.

5. The pressure transducer of claim 4, wherein:

the first and second pressure sensors include first and second diaphragm covered chambers;

the Wheatstone Bridges comprise resistances formed by injecting boron into the diaphragms;

the outputs of the sensors are produced by movements of the diaphragms responsive to pressure differences on each side of the first and second diaphragms.

6. The pressure transducer of claim 5 further comprising:

a voltage biased metallic layer formed over the resistances to prevent ion contaminants from combining with the resistances and changing the resistive values.

7. The pressure transducer of claim 1 wherein the first and second sensors each has a positive and negative output node and the sensors are cross-coupled by electrically connecting the positive output node of the first sensor to the negative output node of the second sensor and the negative output node of the first sensor to the positive output node of the second sensor.

8. The pressure transducer of claim 1, further comprising:

a differential amplifier; and

wherein

the first pressure sensor measures a high pressure and the second pressure measures a reference pressure, of lower pressure than the high pressure; and

one output from the sensors is electrically connected to a positive input of the differential amplifier and another output from the sensors is electrically connected to a negative input of the differential amplifier to produce a differential pressure measurement of the high and reference pressures.

9. The pressure transducer of claim 1, wherein the first and second voltages are adjusted according to the outputs of the sensors.

10. The pressure transducer of claim 1, wherein the first and second voltages are adjusted to compensate for changing temperature.

11. The pressure transducer of claim 10, further comprising a signal conditioner including temperature measuring circuitry and wherein:

ambient temperature is measured by the circuitry of the signal conditioner and, in response to the measured ambient temperature, the conditioner injects first and higher-order error-correcting signals to compensate offset and sensitivity signal errors of each of the sensors.

12. The pressure transducer of claim 1, wherein the first and second voltages are provided by first and second excitation sources controlled by a signal conditioner network, the signal conditioner network adjusting the voltages based on inputs from the sensors to substantially match the sensitivities of the first and second pressure sensors over a range of pressures and temperatures.

13. The pressure transducer of claim 1, wherein:

the first sensor includes a first diaphragm exposed on one side and having a sealed partially evacuated chamber on the other side of the firsts diaphragm, said first sensor providing an output signal proportional to the difference between a first pressure applied across the exposed side of the first diaphragm and a second pressure applied across the chamber side of the first diaphragm; and

the second sensor includes a second diaphragm exposed on one side and having a sealed partially evacuated chamber on the other side of the second diaphragm, said second sensor providing an output signal proportional to the difference between a third pressure applied across the exposed side of the first diaphragm and a fourth pressure applied across the chamber side of the first diaphragm.

14. The pressure transducer of claim 13, wherein:

all four pressures are different from each other.

15. The pressure transducer of claim 1, wherein:

the first sensor includes a first diaphragm exposed on one side and having a chamber on the other side of the first diaphragm, said first sensor providing an output signal proportional to the difference between a first pressure applied across the exposed side of the first diaphragm and an atmospheric pressure applied across the chamber side of the first diaphragm; and

the second sensor includes a second diaphragm exposed on one side and having a chamber on the other side of the second diaphragm, said second sensor providing an output signal proportional to the difference between a third pressure applied across the exposed side of the second diaphragm and the atmospheric pressure applied across the chamber side of the second diaphragm.

16. The pressure transducer of claim 15, wherein:

the first and second sensors have substantially fluid-tight attachments to the substrate sections with walls forming holes passing through each of the substrate sections and into the first and second chambers; and

said walls are disposed to form holes having a diameter large enough to prevent ice formed in the chamber from exerting significant force on the walls of the chamber.

17. The pressure transducer of claim 1, wherein:

the first sensor is fixed relative to a first substrate section and is within a first chimney having a substantially fluid-tight attachment to the first substrate section; and

the second sensor is fixed relative to a second substrate section and is within a second chimney having a substantially fluid-tight attachment to the second substrate section.

18. The pressure transducer of claim 17, further comprising:

a housing;

first and second intakes;

wherein a substantially fluid-tight path is formed between the first intake and the first chimney such that a first fluid path exists from the first intake to the first chimney, and a substantially fluid-tight path is formed between the second intake and the second chimney such that a second fluid path exists from the second intake to the second chimney; and

wherein the first and second chimneys form a substantially fluid-tight space within the housing.

20. The method of claim 19, wherein the step of adjusting the first and second excitations includes increasing the first excitation and decreasing the second excitation so that they substantially match each other.

21. The method of claim 19, wherein the step of cross-coupling the outputs includes electrically connecting a positive output node of the first sensor to a negative output node of the second sensor and electrically connecting the negative output node of the first sensor to the positive output node of the second sensor.

22. The method of claim 19, wherein the step of independently adjusting the first and second excitations includes the step of adjusting the first and second voltages to substantially match the sensitivities of the first and second sensors over a range of pressures and temperatures.

23. The method of claim 19, wherein the step of independently adjusting the first and second excitations includes the step of adjusting the first and second voltages based on inputs from the sensors provided to a signal conditioner network to substantially match the sensitivities of the first and second pressure sensors over a range of pressures and temperatures.

19. A method for matching the output characteristics of a first and a second pressure sensor comprising the steps of:

a) applying a first excitation to the first pressure sensor;

b) applying a second excitation different than said first excitation to the second pressure sensor;

c) independently adjusting the first and second excitations to increase or decrease the sensitivities of the first and second sensors to substantially match each other; and

d) cross-coupling the outputs of the sensors to reduce the offset difference errors between the pressure sensors.

24. A pressure measuring means comprising:

a first pressure sensor having a first sensitivity;

a second pressure sensor having a second sensitivity different than the first sensitivity;

a first excitement means for exciting the first pressure sensor at a first excitement level;

a second excitement means for exciting the second pressure sensor at a second excitement level different than the first excitement, the first and second excitement means independently adjustable to increase or decrease the sensitivities of the first and second sensors to substantially match each other; and

means for cross-coupling the outputs of the sensors to reduce the offset difference errors between the pressure sensors.