Signal processing unit for a pressure switch or the like

• US 7,085,657 B2
• Filed: 11/26/2002
• Issued: 08/01/2006
• Est. Priority Date: 12/11/2001
• Status: Expired due to Fees

• Current Assignee: Parker Hannifin GmbH (Parker-Hannifin Corporation)
• Original Assignee: Parker Hannifin GmbH (Parker-Hannifin Corporation)
• Inventors: Drossel, Detlef
• Primary Examiner(s): Tsai, Carol S. W.
• Assistant Examiner(s): Gutierrez, Anthony
• Application Number:
  US10/305,746
• Publication Number:
  US 20030107509A1
• Time in Patent Office: 1,344 Days
• Field of Search: 702/57, 702/138, 702/189, 702/50, 702 64- 66, 702/106, 702/107, 702/139, 330/9, 327/124
• US Class Current: 702/50
• CPC Class Codes: G01L 19/12 Alarms or signals
• CPC Class Codes: G01L 9/045 with electric temperature compensating means non electric temperature compensating means G01L19/04

Abstract

A signal processing unit for a pressure switch or the like, comprising a sensor element, such as a strain gauge bridge, to supply an analog electrical signal that corresponds to a pressure; a signal processing unit which is connected downstream of the sensor element to amplify and digitize the analog signal; and a control unit for electrical switches which is connected downstream of the signal processing unit to switch external loads or the like. According to the invention, the signal processing unit comprises a chopper amplifier, which switches or balances the polarity of the analog electrical signal present at its input and supplied by the sensor element, and the amplified analog electrical or digitized signal present at its output, at the same clock rate.

Claims

1. A pressure switch comprising:

i) a sensor element to supply an analog electrical signal corresponding to a pressure,

ii) a signal processing unit which is connected downstream of the sensor element to amplify the analog electrical signal, and

iii) a control unit for electrical switches which is connected downstream of the signal processing unit for switching external loads, for a display unit, for production interfaces and the like,

wherein the signal processing unit comprises a chopper amplifier, which switches or balances the polarity of the analog electrical signal present at an input to the signal processing unit supplied by the sensor element, and the analog electrical signal present at an output of the signal processing unit, at the same clock rate,

the output of the signal processing unit supplies a voltage with a magnitude corresponding to a measured quantity sensed by the sensor, and

the output of the signal processing unit is connected upstream of an analog/digital converter which samples the voltage in a first phase and a second phase and converts them into numerical values and enables subtraction of the two values in a unit connected downstream the converter output.

2. The pressure switch as in claim 1, wherein the sensor element comprises a measuring resistor or a measuring bridge, such that the switching of the polarity of the signal present at the input of the chopper amplifier is obtained by supplying a square wave AC voltage as the supply voltage to the measuring resistor or the measuring bridge at the clock rate.

3. The pressure switch as in claim 2, where the sensor element output signal is supplied to the signal processing unit which comprises two operational amplifiers, two inputs, and two outputs representing the output of the signal of the signal processing unit, and which is configured in such a way that at each of the two outputs the signal processing unit supplies a voltage with a magnitude corresponding to a measured quantity sensed by the sensor element.

4. The pressure switch as in claim 3, wherein the two outputs are connected upstream of the analog/digital converter, which alternately samples the two voltages in each of the first phase and the second phase and converts them into numerical values and enables a subtraction of the two values in the unit connected downstream of the converter output.

5. The pressure switch as in claim 4, wherein the unit connected downstream of the converter output comprises a microcontroller unit which includes a switching clock to generate the clock rate.

6. The pressure switch as in claim 5, wherein the subtraction is controlled and/or is performed by the microcontroller unit.

7. The pressure switch as in claim 6, wherein the supply voltage for the measuring resistor or the measuring bridge is supplied by the microcontroller unit.

8. An electronic switch means including:

i) a sensor element to supply an analog electrical signal corresponding to a measured quantity;

ii) signal processing means connected downstream of the sensor element to amplify the analog electrical signal, and

iii) control means connected downstream of the signal processing means to interface with external electrical components;

the signal processing means comprising a chopper amplifier, which switches or balances the polarity of the signal supplied to an input to the signal processing means by the sensor element, and the signal provided at an output of the signal processing means, at the same clock rate,

the output of the signal processing means supplies a voltage with a magnitude corresponding to a measured quantity sensed by the sensor element, and

the output of the signal processing means is connected upstream of an analog/digital converter which samples the voltage in a first chase and a second chase and converts them into numerical values and enables subtraction of the two values in a unit connected downstream the converter output.

9. The electronic switch means as in claim 8, wherein the sensor element comprises electronic measuring means, and switching of the polarity of the signal present at the input of the chopper amplifier is obtained by supplying a square wave AC voltage as the supply voltage to the measuring means at the clock rate.

10. The electronic switch means as in claim 9, where the electronic measuring means provides an output signal which is supplied to the signal processing means which comprises two operational amplifiers, two inputs, and two outputs representing the output of the signal processing means, and which is configured in such a way that at each of the two outputs, the signal processing means supplies a voltage with a magnitude corresponding to the measured quantity sensed by the sensor element.

11. The electronic switch means as in claim 10, wherein the two outputs are connected upstream of the analog/digital converter, which converter alternately samples the two voltages in each of the first phase and the second phase and converts them into numerical values and enables a subtraction of the two values in the unit connected downstream of the converter.

12. The electronic switch means as in claim 11, wherein the unit comprises a microcontroller, which includes a switching clock to generate the clock rate.

13. The electronic switch means as in claim 12, wherein the microcontroller includes means to perform the subtraction of the two values.

14. The electronic switch means as in claim 13, wherein the microcontroller includes means to supply the supply voltage to the electronic measuring means.

15. The electronic switch means as in claim 8, further including external electronic components connected downstream of the control means consisting of at least one of i) a display unit;

ii) switches;

iii) out connectors; and

iv) production interfaces.