Signal processing unit for a pressure switch or the like

• US 20030107509A1
• Filed: 11/26/2002
• Published: 06/12/2003
• Est. Priority Date: 12/11/2001
• Status: Active Grant

• Current Assignee: Parker Hannifin GmbH (Parker-Hannifin Corporation)
• Original Assignee: Parker Hannifin GmbH (Parker-Hannifin Corporation)
• Inventors: Drossel, Detlef
• Granted Patent: US 7,085,657 B2
• Time in Patent Office: Days
• US Class Current: 341/155
• 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

Disclosed is a signal processing unit for a pressure switch or the like, comprising a sensor element, such as a strain gauge bridge (26-1, 26-2, 26-3, 26-4) to supply an analog electrical signal (28-1, 28-2) that corresponds to a pressure, a signal processing unit (32-1, 32-2, 38, 40) 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 (12), which switches or balances the polarity of the analog electrical signal present at its input (34) and supplied by the sensor element (26) and the amplified analog electrical or digitized signal present at its output at the same clock rate.

Claims

1. Signal processing unit for a pressure switch or the like, comprising a sensor element (10), e.g. a pressure sensor, to supply an analog electrical signal corresponding to a pressure or the like, a signal processing unit (12) which is connected downstream of the sensor element to amplify and digitize the analog signal, and a control unit (14) for electrical switches (18) which is connected downstream of the signal processing unit (12) for switching external loads, for a display unit (16), for production interfaces (20) and the like,

characterized in that

the signal processing unit (12) comprises a chopper amplifier, which switches or balances the polarity of the analog electrical signal present at its input supplied by the sensor element (10) and the analog electrical or digitized signal present at its output at the same clock rate.

2. Signal processing unit as claimed in claim 1, wherein the sensor element (10) represents a measuring resistor or a measuring bridge (26-1, 26-2, 26-3, 26-4), characterized in 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 (30-1, 30-2) to the measuring resistor or the measuring bridge at the clock frequency.

3. Signal processing unit as claimed in claim 1 or 2, characterized in that the bridge output signal (28-1, 28-2) is supplied to a circuit which comprises two operational amplifiers (32-1, 32-2), two inputs (34-1, 34-2) and two outputs (36-1, 36-2) and which is configured in such a way that at its two outputs it supplies a voltage (38-1, 38-2) with a magnitude corresponding to the measured quantity, e.g. pressure, sensed by the sensor element (10).

4. Signal processing unit as claimed in claim 3, characterized in that the two outputs (36-1, 36-2) are connected upstream of an analog/digital converter (42), which alternately samples the two voltages (38-1, 38-2) and converts them into numerical values and enables a subtraction of the two values in a unit (40) connected downstream of its output.

5. Signal processing unit as claimed in any one of claims 1 to 4, characterized in that the switching clock is generated in a microcontroller unit (40).

6. Signal processing unit as claimed in claim 5, characterized in that subtraction is controlled and/or is performed by the microcontroller unit (40).

7. Signal processing unit as claimed in claim 4, 5 or 6, characterized in that the supply voltage for the measuring resistor or the measuring bridge is supplied by the microcontroller unit (40).