EP1869409A1

EP1869409A1 - Sensor system

Info

Publication number: EP1869409A1
Application number: EP06743246A
Authority: EP
Inventors: Holger Borst
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2005-04-08
Filing date: 2006-04-05
Publication date: 2007-12-26
Also published as: US20090295413A1; DE102005016127A1; WO2006106111A1; JP2008535112A; CN101156046A; US8154312B2; DE102005016127B4; KR20070121720A; JP4819874B2

Abstract

The invention relates to a sensor system comprising a sensor unit for detecting a measured variable and an evaluation unit. The sensor unit and the evaluation unit are interconnected at least via one or several links. The sensor unit is provided with a sensor which is connected to a supply voltage and encompasses a signal output for a test signal that depends on the measured variable. The evaluation unit is equipped with a voltmeter to detect the state of the measured variable in accordance with a potential. The sensor unit is provided with a first resistive circuit that is connected to the sensor while the evaluation unit is fitted with a second resistive circuit which is connected to the voltmeter. The first and the second resistive circuit are coupled to each other via at least the sensor link while forming a resistive network. The first and the second resistive circuit are designed such that the voltmeter detects one or several measured potentials in one or several defined measured potential ranges in accordance with the measured variable in a faultless state of the one or several links while detecting a measured potential lying within a faulty potential range in case of a fault. The first and the second resistive circuit are dimensioned in such a way that the faulty potential range lies outside the one or several defined measured potential ranges.

Description

sensor system

The invention relates to a sensor system with a sensor unit and one of them locally separated evaluation unit, which are connected to each other at least via a sensor line.

Electronic systems often have an evaluation unit for the provision of measurement signals to be processed in the system. The evaluation unit is usually part of a control or regulating system and communicates via one or more connecting lines with a sensor unit, which is arranged away from the system. The connecting line between the evaluation unit and the sensor unit can be interrupted under harsh operating conditions, such as may occur in a motor vehicle, for example, or be short-circuited to other connecting lines. This may u.U. lead to a malfunction of the system without the error being detected if the measured quantity supplied by the sensor unit is plausible.

The safety in operation of the system with the evaluation unit and the external sensor unit can be increased by performing a diagnosis of the connection line to the above-mentioned error. For this purpose, a voltage measured on the connecting line is usually made plausible. To break the cable at the sensor supply, i. H. on the corresponding connection lines, which carry the supply voltage to determine, is e.g. the voltage drop across a measuring resistor in the connecting cable

(Shunt) monitors. When properly connected, the supply current of the sensor unit causes a voltage drop that can be measured. If the voltage drop does not exist, it can be concluded that there is a broken line. Is - provided that the sensor unit is with a smaller supply voltage than the evaluation unit of the entire system - the voltage after the resistor is too large this is a short circuit behind the voltage supply of the evaluation unit. If the measured voltage is too small, there is a short circuit to a ground potential. The voltage swing of the output of the sensor unit is increased to values greater than 0 V by means of appropriate wiring with resistors

(Ground potential) and less than the supply voltage of the sensor unit limited to distinguish the regular operation of short circuits to ground and the supply voltage of the sensor unit or the evaluation.

Due to tolerances of the supply current of the sensor unit and tolerances of the resistance of the supply lines and the sensor unit over the life and the temperature results in significant voltage drop across the measuring resistor, which may lead to high power losses in the measuring resistance in the power supply, so that large designs are used need to be able to absorb a correspondingly large output. Furthermore, a measuring resistor and a corresponding measuring channel in the evaluation unit is required for each connecting line to be diagnosed.

This is usually expensive and the overall device has a lot of space.

It is an object of the present invention to provide a sensor system with an evaluation unit and with an external sensor unit which is of simple construction and is able to detect interruptions of connecting lines reliably and with a low circuit complexity.

This object is achieved by the sensor system according to claim 1.

Further advantageous embodiments of the invention are specified in the dependent claims. According to the invention, a sensor system is provided which has an evaluation unit and a sensor unit arranged externally thereof for detecting a measured variable. The sensor unit and the evaluation unit are connected to one another via one or more connecting lines. The sensor unit has a sensor which is connected to a supply voltage and comprises a signal output for a measurement signal dependent on the measured variable. The evaluation unit has a voltage detector in order to detect the state of the measured variable as a function of a potential. The sensor unit comprises a first resistance circuit, which is connected to the sensor, and the evaluation unit, a second resistance circuit, which is connected to the voltage detector. The first and second resistance circuits are coupled to each other via the one or more connection lines and form a resistance network. The first and second resistance circuits are designed so that the voltage detector detects one or more measuring potentials in one or more defined measuring potential ranges depending on the measured variable in a fault-free state of the one or more connecting lines of the sensor system and detects a measuring potential in an error case an error potential range lies. The first and second resistance circuits are dimensioned such that the fault potential range lies outside the one or more defined measuring potential ranges.

In the present sensor system, it is possible in a simple manner, by means of the resistance circuits provided both in the sensor unit and in the evaluation unit,

Define measuring potential ranges and different error potential ranges, which enable a measurement to detect the state of the measured variable, or, if an error has occurred on the one or more connecting lines, to recognize and identify this error based on the associated error potential range. This can according to the invention with only one voltage detector in the Evaluation unit can be performed so that the structure of the sensor system can be performed in a simple manner and space-saving.

According to one embodiment of the invention, the first and / or the second resistance circuit are each formed as a resistor chain.

Preferably, the first and the second resistance circuit can be designed such that, in the case of several fault cases, multiple measurement potentials can be detected in a plurality of fault potential areas in order to identify the type of the respective fault.

In particular, the first and the second resistance circuit can be designed so that the voltmeter detects a measuring potential in the event of an interruption of one of the connecting lines, which lies in a respective error potential range associated with the type of fault.

According to a preferred embodiment of the invention, the sensor unit and the evaluation unit are connected to one another via a sensor line, a first and a second supply line. In this way, the sensor unit is provided with a supply voltage via the evaluation unit and the sensor unit can provide the corresponding measured variable via the sensor line of the evaluation unit.

Furthermore, the first and the second resistance circuit can each be designed as a resistor chain, which are connected to each other at different nodes via the sensor line and the first and second supply line. The resistor network has resistance elements which are dimensioned such that, when one of the connection lines is interrupted, the measuring potential is set to the corresponding potential range of the potential. According to a preferred embodiment, the first resistance circuit comprises a first, a second and a third resistance element, which are connected in series between the first supply line and the second supply line. A first node between the first and second resistive elements is connected to the sensor line and a second node is connected between the second and third resistive elements to the signal output of the sensor.

It can further be provided that the second resistance circuit has a fourth, a fifth and a sixth resistance element, which are connected in series between the first supply line and the second supply line, wherein a third node between the fourth and the fifth resistance element with the Sensor line is connected and a fourth node between the fifth and the sixth resistive element is connected to the voltmeter.

The first to sixth resistive elements can be dimensioned such that the faults can be identified unambiguously by interrupting one of the connecting lines on the basis of the fault potential range in which the measuring potential is measured.

According to a preferred embodiment, the sensor may be a logic sensor with digital output, wherein the sensor comprises a switch which is connected in parallel to one of the first to third resistors and which is either closed or opened depending on the detected state. In particular, the sensor may comprise a Hall sensor.

Preferred embodiments of the present invention will be explained in more detail below with reference to the accompanying drawings. Show it: Figure 1 is a block diagram of a sensor system according to a first embodiment of the invention;

FIG. 2 shows a sensor system according to a further embodiment of the present invention;

FIG. 3 shows the arrangement of measuring and fault potential ranges in the embodiment of FIG. 2.

FIG. 1 shows an electronic system which has, in a control system R, an evaluation unit 1 for an externally arranged sensor unit 2 and a control unit 3. The evaluation unit 1 acquires a measured value and makes it available to the control unit 3 as a control value on an output line 4, so that the control unit 3 of the control system depends on the control value, e.g. can control another electronic device.

The evaluation unit 1 serves to establish a connection with a sensor unit 2 arranged externally of the electronic system via connecting line 5. Such a separate arrangement of control system and sensor unit 2 is particularly useful in harsh environmental conditions in which measured values must be recorded. To protect the electronics of the control system, this is therefore arranged separately from the sensor unit 2.

A power supply of the sensor unit 2 is ensured via a voltage source 6 in the evaluation unit 1. For this purpose, the evaluation unit 1 provides a first supply voltage potential on a first supply line 7 and a second supply potential on a second supply line 8 of the sensor unit 2. The sensor unit 2 supplies an output measurement signal to a sensor line 9, which is connected to a separate input of the evaluation unit 1. The evaluation unit 1 has an analog-to-digital converter 10, which generates the control value for output on the output line 4. The sensor unit 2 has a sensor 11 which, depending on a measured variable, such as eg a temperature, a pressure or another variable, generates a measuring signal MS.

The sensor 11 is connected to the first and the second supply line 7, 8 in order to provide the sensor 11 with a supply voltage. The sensor unit 2 has a first resistance circuit 12, which is connected to the first and the second supply line 7, 8, the sensor line 9 and the output of the sensor 11. The evaluation unit 1 has a second resistance circuit 13 which is connected to the first and second supply lines 7, 8, the sensor line 9 and an input of the analog-to-digital converter 10. The first and second resistance circuits 12, 13 are therefore connected to one another via the first and second supply lines 7, 8 and the sensor line 9 and form a resistance network in their common connection. This resistor network comprising first and second resistance circuits 12, 13 supplies, in the error-free operating state at the input of the analog-to-digital converter, a measuring potential which depends on the measuring signal MS at the output of the sensor 11.

The resistor network is further designed so that in the event of an error, such as in the case of an interruption of one of the connecting lines 5, a measuring potential is applied to the analog-to-digital converter 10, which lies in a different potential range than the potential range in which the measuring potential is in proper operation.

Preferably, the resistor network forms a voltage divider which is formed by the connection of the first and the second resistance circuit 12, 13. If one of the connecting lines between the two resistance circuits 12, 13 is interrupted, this will change the resistance Conditions of the voltage divider, and the measuring potential at the input of the analog-to-digital converter 10 adjusts independently of the measurement signal or only to a small extent of the measurement signal depending on a potential that lies in a potential range of error potential. As a result, it can be determined that there is an error and what kind of error is. Since the sensor 11 no longer operates properly when one of the first or second supply lines 7, 8 stops and, on the other hand, when the sensor line 9 is interrupted, no measuring potential can be detected which depends on the measuring signal of the sensor 11, the fault potential ranges in the exemplary embodiment shown are essentially independent of the state of the sensor 11. Furthermore, by suitable dimensioning of the first and the second resistance circuit 12, 13 fault potential ranges for each possible fault on different potential ranges are set, so that it can be detected on the basis of the measurement potential, whether the state of the connecting lines to the sensor unit 2 is error-free or an error in the form of a Interruption of one of the connecting lines 5 is present.

Even short circuits between the connecting lines 5 can be detected and in particular a short circuit between the second supply line 8 and the sensor line 9 can be detected, so that it is advantageous to distinguish the individual types of error, the potential error areas for displaying the error of breaks in the connecting lines of 0 V in different potential areas to lay.

FIG. 2 shows a more detailed illustration of a possible embodiment of the present invention. As sensor 11, a Hall sensor in the form of a HalI ICs is provided, which identifies an open-collector output. Ie. Depending on the state of measurement of the Hall sensor, the output is connected to the applied potential on the second supply line 8 or switched to high impedance. The first resistance circuit comprises a first resistor Ri, a second resistor R2 and a third resistor R ₃ which are connected in series between the first supply line 7 and the second supply line. 8 A first node K1 between the first and second resistors Ri, R ₂ is connected to the sensor line 9. A second node K2 between the second resistor R ₂ and the third resistor R ₃ is connected to the output of the Hall sensor, which provides the measurement signal MS.

The second resistance circuit 13 of the evaluation unit 1 has a fourth resistor R4, a fifth resistor R ₅ and a sixth resistor Re, which are arranged in series between the first supply line 7 and the second supply line 8. A third knot K3 between the fourth resistor and the fifth resistor R4, _R5 is connected to the sensor line. 9 A fourth node K4, which is situated between the fifth resistor _R5 and the sixth resistor Re is, nalogue-digital converter at the input of the A to 10 to provide to the measuring potential are available.

The resistance network formed by the first resistance circuit 12 and the second resistance circuit 13 is arranged distributed in the evaluation unit 1 and the sensor unit 2, wherein the connecting lines 5 each cause a parallel connection of the resistors. For example, the first supply line 7 and the sensor line 9 cause the first resistor R 1 and the fourth resistor R ₄ to form a total resistance in a voltage divider formed by the entire resistor network. If one of the connecting lines 5 is interrupted, the resulting parallel connection of the corresponding resistors is eliminated, so that the measuring potential at the fourth node K4 jumps to a potential in a corresponding error potential range which is independent of the measuring signal MS of the Hall sensor 11 is, since this is not functional either by an interruption of the first and second supply line 7, 8 or the signal corresponding to the measuring signal can no longer be transmitted to the evaluation unit 1 in the event of an interruption of the sensor line 9.

In Figure 3, the potential ranges are exemplary Vi-V _SS for measuring potentials in a fault-free condition, and shown in possible interruptions of the three connecting lines. Furthermore, a potential range at 0 V is provided which is taken up by the measuring potential if a short circuit has occurred between the sensor line or the first supply line and the second supply line. The potential ranges correspond to a certain potential range resulting from tolerances and disturbances. If it is determined in the control unit that the measured measurement potential is within such a range, the state of the system assigned to the potential range is assumed.

While the potential range denoted by Vo indicates that the first supply line 7 or the sensor line 9 is short-circuited to the second supply line 8, the potential regions which are identified by Vi and V ₃ indicate the regions which correspond to the detection states of the Hall sensor 11 in error-free Operating condition correspond. The potential range Vi results from the following formula,

and the potential range V ₃ results

y_y. * 6. (* 2 + * 3) | | (*, + * ₆ )

^{3 vers} R _{5 +} R ₆ R ₁ WR _{4 +} (R _{2 +} R ₃ ) W (R _{5 +} R ₆ ) wherein the output of the Hall sensor 11 is switched to high impedance. The potential range V ₃ results from the state of the Hall sensor 11, in which the output terminal is connected to the potential of the second supply line 8, for example a ground potential.

The potential region V ₂ is an error potential range indicating an interruption of the first supply line 7. The potential range V ₂ is given by the following formula:

If the sensor line 9 is interrupted, then the measuring potential is within the potential range V4, which can be determined according to the following formula:

A potential in the potential region V ₅ is measured when the second supply line 8 is interrupted. The potential range V ₅ results from the formula:

The resistance values of the resistors Ri to Re are preferably selected so that none of the potential ranges overlap or overlap.

The embodiment shown here comprises a sensor which outputs only two output states. However, it is also possible to use a sensor 11 which outputs an analog measurement signal in a certain range. The resistance values of the resistors Ri to Re are preferably to provide such that there is no fault potential range within this measuring potential range predetermined by the measuring signal, so that a clear distinction can be made between proper operation and fault case on the basis of the measuring potential.

The above-mentioned calculation formulas for determining potential ranges merely indicate the arithmetical mean value of the potential ranges, ignoring collector saturation current of the Hall transistor, the range of the ranges being determined by tolerances and disturbances. When dimensioning the resistance values, it must be ensured that the fault potential ranges or the measuring potential ranges do not overlap. For this purpose, for example, the potential range determined by the mean value given by the formulas given above can be provided with a tolerance range which is determined by the specification that the individual potential ranges must have a certain distance from each other. Possible combinations of resistances are determined iteratively or by trial-and-error. For example, as in the embodiment shown here, the resistance values Ri to R ₆ can be determined with the aid of the following inequality for a given span of the respective potential range of 0.1 V.

V ₁ + I-0.05F <V ₂ + I-0.05F <V ₃ + 1-0.05F <V ₄ + 1-0.05F <V ₅ + 1-0.05F

From such an inequality it is possible to determine iteratively possible combinations of resistance values for the first to sixth resistance. For example, the values of the resistances may have the following values: Ri = 2.15kΩ, R ₂ = lkΩ, R ₃ = 3.09kΩ, R ₄ = 825Ω, R ₅ = 1.5kΩ and R ₆ = 75Ω.

The resistance circuits 12, 13 can also be constructed in a different way, but it is important that the two resistance circuits 12, 13 form a resistance network which, depending on the possible error situation, can be subject to a fault. has a different impact on a measurement potential. In particular, however, it is desirable that both the first supply line 7 and the second supply line 8 are as far as possible not subject to resistance, so that no significant drop in the supply voltage up to the sensor unit 2 occurs.

The table below will assist in setting resistors Ri to Re, with the effect of changing the corresponding resistance indicated in the rows to the potential ranges indicated as column headings represented by the size of the letters. In this case, k means a reduction and g an increase in the resistance value. To mark a particularly small influence of a change in the resistance value, the letters g and k are in brackets.

First, the resistances Ri, R ₃ to Rζ are set, wherein the resistance values of the resistors Ri and R _{4 are} selected to be identical, so that the voltage at the node K4 is smaller than a reference voltage of the A / D converter to also state a short circuit to be able to recognize the sensor line to the first supply line. Subsequently, the resistance value of the resistor R _{2 is} set to set the potential range for a first detection state, that is, to set the potential range V ₃ , and then the resistance of the resistor R _{3 is set} for a second detection state, which is determined by the potentiometer. albereich Vi is indicated. The resistance values of the resistors, which have the greatest possible influence on the potential range to be taken from the table in order to achieve a good separation of the potential ranges for the different fault states, are now preferably varied with the aid of the table given above.

Claims

claims

1. sensor system having a sensor unit (2) for detecting a measured variable and having an evaluation unit (1) which are connected to the sensor unit via one or more connecting lines (7, 8, 9),

- wherein the sensor unit (2) comprises a sensor (11) which comprises a signal output for a measurement signal dependent on the measurement variable (MS); - wherein the evaluation unit (1) has a voltage detector

(10) in order to detect the state of the measured variable as a function of a potential, characterized in that the sensor unit (2) has a first resistance circuit (12) which is connected to the sensor, and the evaluation unit (1) has a second resistance circuit ( 13) coupled to the voltage detector (10), the first and second resistor circuits (12, 13) being coupled in common across the one or more interconnect lines (7, 8, 9) and forming a resistive network, the the first and the second resistance circuit (12, 13) are designed so that the voltage detector (10) in a faultless state of the one or more connecting lines (7, 8, 9) one or more measuring potentials in one or more defined measuring potential ranges depending on Measured detected and detected in a fault, a measuring potential, which is in an error potential range, the outside of the one or more definie ranges of measurement potentials.

2. Sensor system according to claim 1, wherein the first and / or the second resistance circuit (12, 13) are each formed as a resistor chain.

3. Sensor system according to claim 1, wherein the first and the second resistance circuit (12, 13) are formed so that in the case of several error cases by a plurality of measurement potentials in corresponding multiple error potential areas are detectable to detect the nature of the respective error case.

4. Sensor system according to claim 3, wherein the first and the second resistance circuit (12, 13) are designed so that the voltage detector (10) detects a measuring potential when an interruption of one of the connecting lines, which is located in a respective fault type associated with the error type ,

5. Sensor system according to one of claims 1 to 4, wherein the sensor unit (2) and the evaluation unit (1) with each other via a sensor line (9), a first and a second supply line (7, 8) are connected.

6. A sensor system according to claim 5, wherein the first and the second resistance circuit (12, 13) are each formed as a resistor chain, which are connected together at different nodes via the sensor line (9) and the first and second supply line (7, 8), wherein resistance elements (Ri-R _ß ) of the resistor network are dimensioned so that when interrupting one of the connecting lines (7, 8, 9), the measuring potential is set to the corresponding error potential range.

A sensor system according to any one of claims 5 and 6, wherein the first resistance circuit (12) comprises first, second and third resistance elements (Ri, R2, R ₃ ) arranged in series between the first supply line (7) and the second Supply line (8) are connected, wherein a first node (Kl) between the first and the second resistance element (Ri, R2) is connected to the sensor line and a second node (K2) between the second and the third resistance element with the signal output connected to the sensor.

8. The sensor system of claim 7, wherein said second resistance circuit (13), a fourth, a fifth and a sixth resistance element having _(R4-R6), connected in series between the first supply line (7) and the second supply line (8) wherein a third node (K3) between the fourth and the fifth resistive element (R4, _R5) connected to the sensor line (9) and a fourth node (K4) between the fifth and the sixth resistance element (R ₅ -R ₆₎ is connected to the voltage detector (10).

9. Sensor system according to claim 8, wherein the first to sixth resistive element (Ri-Rβ) are dimensioned so that the error by interruption of one of the connecting lines uniquely on the basis of the fault potential range in which the measuring potential is identifiable.

10. Sensor system according to claim 8 or 9, wherein the first to sixth resistive element (Ri-Rβ) are further dimensioned so that the errors are clearly identified by shorting one of the sensor line with a fixed potential based on the measuring potential.

11. A sensor system according to any one of claims 1 to 10, wherein the sensor (11) is a logic sensor with digital output, wherein the sensor (11) comprises a switch which is connected in parallel to one of the first to third resistor and which depends on the sensor state is either closed or open.

12. Sensor system according to one of claims 1 to 11, wherein the sensor comprises a Hall sensor.