GB2334588A - Monitoring correct operation of a sensor module comprising a Wheatstone bridge circuit - Google Patents

Monitoring correct operation of a sensor module comprising a Wheatstone bridge circuit Download PDF

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Publication number
GB2334588A
GB2334588A GB9901498A GB9901498A GB2334588A GB 2334588 A GB2334588 A GB 2334588A GB 9901498 A GB9901498 A GB 9901498A GB 9901498 A GB9901498 A GB 9901498A GB 2334588 A GB2334588 A GB 2334588A
Authority
GB
United Kingdom
Prior art keywords
bridge
sensor module
sensor element
integrated circuit
sensor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9901498A
Other versions
GB9901498D0 (en
Inventor
Gerald Brinks
Thomas Ohgke
Gunther Schuster
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Conti Temic Microelectronic GmbH
Original Assignee
Temic Telefunken Microelectronic GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Temic Telefunken Microelectronic GmbH filed Critical Temic Telefunken Microelectronic GmbH
Publication of GB9901498D0 publication Critical patent/GB9901498D0/en
Publication of GB2334588A publication Critical patent/GB2334588A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R17/00—Measuring arrangements involving comparison with a reference value, e.g. bridge
    • G01R17/10—AC or DC measuring bridges
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
    • G01L27/007—Malfunction diagnosis, i.e. diagnosing a sensor defect
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
    • G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P21/00—Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

A sensor module consists of a sensor element 12 for detecting a physical quantity, in particular, pressure and acceleration, and at least one integrated circuit 10, wherein at least one Wheatstone bridge 13 producing at least two output signals is arranged on the sensor element. Window comparators 15, 15 are formed in the integrated circuit for producing a fault indication if the output signals exceed or fall below predefined limiting values. Ageing of the wire bond connections, disruptions in the electrical contacts between the sensor element and the signal processing unit or even short circuits due to moisture for example can thereby be recognised and diagnosed as sources of trouble. Furthermore, by using two window comparators simultaneously, each output signal from the Wheatstone bridge is checked and displacements of the bridge level are detected.

Description

SENSOR MODULE The invention relates to a sensor module consisting of a sensor element for detecting a physical quantity and at least one integrated circuit, wherein at least one test bridge is arranged on the sensor element, said bridge being, in particular, a Wheatstone bridge producing at least two output signals.
Various sensor modules of this type are known. The sensor modules consist of a sensor element and a signal evaluating circuit located on an integrated circuit. The sensor element is, in particular, a piezoelectric, piezoresistive or capacitive acceleration sensor. Such types of sensors for measuring physical quantities such as pressure or acceleration for example consist in turn of a moving part, the so-called seismic mass, and a fixed part. The moving and stationary parts are connected together by means of one or more web members. The deflection of the moving part relative to the stationary part represents a measure for the level of acceleration or the amount of pressure. The mechanical signal - the deflection of the moving part - is thereby converted into an electrical signal. A Wheatstone bridge is arranged on the sensor element for accurately measuring the electrical signal. In this case, the piezoelectric resistances form the resistance elements of the Wheatstone bridge. The output signals of the Wheatstone bridge are passed on to a signal evaluating unit. The signal is evaluated in this signal evaluating unit and processed ready for further use.
Several disadvantages arise here: - Changes in the bridge level or threshold of the Wheat stone bridge are not taken into account in the case of the piezoresistive sensor elements. The reason for these changes lies in the ageing of the wire bond connections whereby their resistance increases and the voltage drop across these otherwise low resistance connections adopts inadmissible values.
- In addition, disruptions in the electrical contacts due to bonds lifting or - a low resistance parasitic connection caused by moisture or dirt, especially a short circuit to the supply voltage, are not detected by these sensor modules.
The present invention seeks to overcome or reduce one or more of the disadvantages arising in the case of a sensor module of the type mentioned hereinabove.
According to the present invention there is provided a sensor module consisting of a sensor element for detecting a physical quantity and at least one integrated circuit for evaluating the signals from the sensor, wherein at least one test bridge is arranged on the sensor element to produce at least two output signals (Voutpos, Voutneg), wherein the integrated circuit comprises at least one window comparator which compares at least one output signal (Voutpos, Voutneg) from the test bridge with a defined maximum or minimum value to detect at least one inadmissible bridge level (VPP, VPN) on the test bridge.
Thus, in embodiments of the present invention, at least one integrated circuit comprises at least one window comparator which compares at least one output signal from the test bridge with a defined, permissible maximum or minimum value whereby inadmissible changes in the bridge levels of the test bridge will be detected. Space can thereby be saved, costs reduced and the functioning of the sensor elements be monitored. Ageing of the wire bond connections, disruptions in the electrical contacts between the sensor element and the signal processing unit or even short circuits due to moisture for example can thereby be recognised in a simple manner.
Advantageous developments arise from an arrangement of at least two window comparators which simultaneously detect and evaluate the two output signals of a Wheatstone bridge. The source of error can thereby be localised even more precisely.
A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawing which shows a circuit for monitoring the bridge levels.
Four resistors 5 forming a Wheat stone bridge 13 are located on the sensor element 12 in the case of piezoresistive accelerometers or pressure sensors. The main feature of the Wheatstone bridge is that it is very sensitive to even the smallest changes of resistance i.e. small changes in the resistance of the piezoelectric resistances 5 can be measured very precisely. In this embodiment, the four individual resistors are four, theoretically equally large piezoelectric resistances 5 the values of which alter and thereby unbalance the bridge due to the effect of a physical quantity such as e.g. pressure or acceleration. The bridge voltage VB is proportional to the effective physical quantity such as pressure or acceleration for example. An inadmissible displacement of the bridge level may thereby occur. Here, the bridge levels VPP and VPN are the voltage drops between the respective output signals Voutpos and Voutneg and earth. These inadmissible displacements may occur, due to ageing of the wire bond connections, relative to earth or relative to the voltage supply for the sensor element Vdds. Here, the voltage Vdds is dependent on the operating conditions such as the operating temperature for example. The total resistance increases and the voltage drop in the otherwise low resistance wire bond connections attains inadmissible values.
In addition, the electrical contact to earth, Vdds, Voutpos and Voutneg between the sensor 12 and the integrated circuit 10 may be disrupted, in particular, due to lifting of the bonds. A short circuit caused by moisture is another source of trouble resulting in displacement of the bridge level. The bridge level is permanently monitored by this circuit in order to exclude faults of this type. The output signals Voutpos and Voutneg of the Wheatstone bridge are supplied to the window comparators 14, 15 and monitored thereby. The switching thresholds are defined as follows: Vdds Vdds V1 = ---- - T and V2 = ---- + T 2 2 The variable T represents the voltage value about which the bridge level may deviate by Vdds/2 when the arrangement is functioning properly. The voltage values V1 and V2 are constantly checked in a second monitoring unit 16. The signal ONE is present at the output AF when the bridge level lies within the specified limits V1 and V2. In the case of a fault i.e. either Voutpos or Voutneg or Voutpos and Voutneg exceed(s) the threshold(s) V1 or V2, then the signal ZERO is produced at the output AF.
Sensor modules of this type may also be equipped with capacitive or other types of test bridge which produce a plurality of output signals.

Claims (4)

  1. Claims 1. A sensor module consisting of a sensor element for detecting a physical quantity and at least one integrated circuit for evaluating the signals from the sensor, wherein at least one test bridge is arranged on the sensor element to produce at least two output signals (Voutpos, Voutneg), wherein the integrated circuit comprises at least one window comparator which compares at least one output signal (Voutpos, Voutneg) from the test bridge with a defined maximum or minimum value to detect at least one inadmissible bridge level (VPP, VPN) on the test bridge.
  2. 2. A sensor module according to claim 1, wherein the test bridge is a Wheatstone bridge.
  3. 3. A sensor module according to claim 1 or 2, wherein at least one integrated circuit comprises at least two window comparators which simultaneously detect and evaluate the two output signals (voutpos, Voutneg) of a test bridge (13) and thus the bridge level(s) (VPP, VPN) thereof.
  4. 4. A sensor module substantially as herein described with reference to the accompanying drawing.
GB9901498A 1998-02-18 1999-01-22 Monitoring correct operation of a sensor module comprising a Wheatstone bridge circuit Withdrawn GB2334588A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE1998106753 DE19806753A1 (en) 1998-02-18 1998-02-18 Error indicator for sensor comprising Wheatstonebridge

Publications (2)

Publication Number Publication Date
GB9901498D0 GB9901498D0 (en) 1999-03-17
GB2334588A true GB2334588A (en) 1999-08-25

Family

ID=7858154

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9901498A Withdrawn GB2334588A (en) 1998-02-18 1999-01-22 Monitoring correct operation of a sensor module comprising a Wheatstone bridge circuit

Country Status (3)

Country Link
DE (1) DE19806753A1 (en)
FR (1) FR2775081A1 (en)
GB (1) GB2334588A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6433554B1 (en) 1999-12-20 2002-08-13 Texas Instruments Incorporated Method and apparatus for in-range fault detection of condition responsive sensor
WO2008113883A1 (en) * 2007-03-16 2008-09-25 Risto Hedman Diagnosing an electronic sensor
CN111238724A (en) * 2020-01-18 2020-06-05 天水逢泰科技有限责任公司 High-precision pressure transmitter aging test system test device

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6422088B1 (en) * 1999-09-24 2002-07-23 Denso Corporation Sensor failure or abnormality detecting system incorporated in a physical or dynamic quantity detecting apparatus
DE10133525B4 (en) * 2001-07-11 2010-08-05 Robert Bosch Gmbh Sensor with self-test function
DE10304024B4 (en) * 2002-02-15 2015-08-20 Continental Teves Ag & Co. Ohg Method and circuit arrangement for checking a pressure sensor arrangement
US9084550B1 (en) * 2007-10-18 2015-07-21 Innovative Surgical Solutions, Llc Minimally invasive nerve monitoring device and method

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0592205A1 (en) * 1992-10-07 1994-04-13 Nec Corporation Semiconductor sensor with fault detecting circuit

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5418453A (en) * 1993-11-09 1995-05-23 Delco Electronics Corporation Method of measuring wheel speed sensor impedance
JPH09178512A (en) * 1995-12-28 1997-07-11 Mitsubishi Electric Corp Sensor system and sensor

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0592205A1 (en) * 1992-10-07 1994-04-13 Nec Corporation Semiconductor sensor with fault detecting circuit

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6433554B1 (en) 1999-12-20 2002-08-13 Texas Instruments Incorporated Method and apparatus for in-range fault detection of condition responsive sensor
WO2008113883A1 (en) * 2007-03-16 2008-09-25 Risto Hedman Diagnosing an electronic sensor
US8305100B2 (en) 2007-03-16 2012-11-06 Risto Hedman Diagnosing an electronic sensor
CN111238724A (en) * 2020-01-18 2020-06-05 天水逢泰科技有限责任公司 High-precision pressure transmitter aging test system test device

Also Published As

Publication number Publication date
DE19806753A1 (en) 1999-09-02
FR2775081A1 (en) 1999-08-20
GB9901498D0 (en) 1999-03-17

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)