DE10141331B4 - Method for offset calibration of a sensor signal and sensor arrangement for performing the method - Google Patents

Abstract

method for the offset calibration of a sensor signal in which under the influence a measured variable to be determined on Output of a sensor applied sensor signal in one to one Sensor arrangement belonging Sensor signal processing circuit is edited by using amplification factor other than zero, with a calibration signal and as a sensor output signal is issued, characterized in that in the manufacture of the sensor (3) in the sensor signal processing circuit (4) Flag in a non-volatile Memory (14) is set to a first value that at a Commissioning of the sensor (3) the sensor (3) a defined Value of the measured variable exposed a calibration process is controlled automatically or manually triggered when the flag has the first value, with the calibration process the value of the calibration signal is changed until a corresponding value of the measured variable Sets the sensor output signal and the value of the Calibration signal or a suitable for generating this value Size as a calibration value in the sensor signal processing circuit ...

Description

The The invention relates to a method for offset calibration of a sensor signal, in the case of a measured variable to be determined, one at the output sensor signal applied to a sensor arrangement belonging Signal processing circuit is processed. It will be with amplification factor other than zero, with a calibration signal and as a sensor output signal output.

The The invention also relates to a sensor arrangement with a sensor and a sensor signal processing circuit, which is an amplifier, a non-volatile Includes calibration value memory and an adding point.

With the German patent DE 198 44 663 C2 A circuit arrangement and a method for setting switching points of a decision-maker controlled by an analog input signal are known.

at this circuit arrangement is an arrangement for evaluation of sensor signals, preferably Hall sensor signals, with which dynamic non-electrical measurands such as movement / speed or the position of rotating parts.

The analog electrical output signal of the sensor used the evaluation circuit as its analog electrical input signal, at the output of which one cleaned of disturbance variables and in its Provides adjusted electrical measurement parameters.

in this connection at the end of the measuring chain: measuring object sensor evaluation circuit a pulse train of electrical signal with its frequency as a representative measurement of this Evaluation circuit offered for further processing.

In order to is realized that the exact functioning of the output of this Evaluation circuit located decision maker a significant influence on the accuracy and interference suppression of this Has evaluation circuit.

Regarding the procedural features is this method and its embodiments as to characterize an adaptive / dynamic process in which the switching points of the decision maker by means of various steps auto search to be controlled at the entrance of the decision maker along with superimposed on the useful signal pending interference signal to compensate.

there will before execution of the various steps, the faulty one caused by the interference signal Deviation of the output signal of the decision maker together with the detected DC component and the signal position at its input and rated.

in the With regard to the calibrations required by the prior art it can be stated that with this solution by a subsequent adjustment of switching points to compensate for the DC component at the input of the decision maker improves the way this decision maker works will, but it will not be the calibration of the entire measuring chain allows.

Furthermore, the Japanese patent JP 05203459 A an arrangement is known in which the offset and gain values of a measuring device for electrical measured variables (voltage) are largely ensured independently of the disturbance variable temperature.

This is achieved in that during certain Calibration cycles over a multiplexer successively to the input of the mass measuring device and a reference voltage is applied.

The Measured values applied are calibrated with data sets of correction values that beforehand in a special measuring cycle with the mass applied and when the reference voltage is applied with different ones Temperatures are determined and stored in memory with corresponding flags marked in the evaluation circuit.

in the A temperature monitor determines normal operation of the measuring device the temperature and thus the one marked with the corresponding flag Storage space of the data record for the assigned temperature correction values from the current offset and gain value brought to processing.

Also with this solution it can be seen that a calibration of the entire measuring chain is not carried out, but it is carried out by means of temperature-dependent correction calculations with assigned comparison values only a temperature stabilization the intermediate sizes of amplifier voltages reached. About that In addition, the time drifts that are so important in calibration processes Measuring chain generally not taken into account.

Sensor arrangements of the type mentioned at the outset have to be calibrated to emit a defined sensor output signal. This calibration follows two aspects, namely one Calibration of the slope and an offset calibration. When the slope is calibrated, the gain in the sensor signal processing circuit is adapted to the slope of the sensor in such a way that changes in measured variables at the input of the sensor bring about a corresponding change in the sensor signal output variable. In the case of offset calibration, care is taken to ensure that a fixed value of the measured variable also produces one of the sensor output signal defined as zero value. The present invention relates only to offset calibration.

To the calibration, which is mostly used as a basic calibration for the Manufacturing is done, sensors supply by manufacturing fluctuations differ in their sensor signal behavior, in the frame their accuracy identical output signals with the same measured variables.

Becomes a sensor arrangement calibrated in this way is now installed in a device, So it can happen that during installation due to mechanical stress the sensor shifts the zero point. For example, the Zero value of the measured variable not more the associated Sensor output signal output. As a result, recalibration is required which eliminates the new offset.

It is known for this offset caused by the use of mechanical Means to counter. You can On the one hand, installation instructions are issued that are used must be carefully observed, for example, by a maximum torque when screwing in a sensor must not be exceeded. A different possibility consists in providing a mechanically stable housing for the sensor, which minimizes the input offset.

signal side the installation offset can be compensated for by a recalibration value as a correction factor in a to the output of the sensor signal processing circuit connected device is set and saved. However, this has the disadvantage that, especially when connecting a variety of sensor arrangements to an evaluation device, for every individual sensor arrangement a separate storage of the recalibration value must be provided and that this recalibration is manual for each individual sensor must be made which significantly increases the amount of work.

The The task of the now consists in the effort to eliminate a by using a sensor-related offset.

the method, the task is solved by that in the manufacture of the sensor arrangement in the to the sensor arrangement belonging Signal processing circuit a flag in a non-volatile Memory is set to a first value. When commissioning the sensor arrangement, the sensor is exposed to a defined value of the measured variable. A calibration process is controlled automatically or manually fires if the flag has the first value. During the calibration process the value of the calibration signal is changed until the defined one Corresponding value of the measured variable Sensor output signal. The value of the calibration signal or a quantity suitable for generating this value is stored in the sensor signal processing circuit as a non-volatile calibration value saved. Subsequently the flag becomes a second value different from the first value set.

By this procedure will make it possible for that the sensor arrangement after use, that is after the sensor was installed with regard to the offset itself calibrated. It is only necessary to read the sensor installation and before the first start-up with a defined To apply the measured variable, for the the sensor output signal to be reached is known. Then will the sensor started up, for example, by being turned on or otherwise supplied with operating voltage. Because the manufacturer Flag is still set to the first value, the automatic takes place Calibration to the defined sensor output signal value. To The flag is then saved to the corresponding calibration value set a different value, which means that the next time you start up the calibration process is not repeated again. This makes it possible to Sensor arrangement under exposure to undefined measurement variables and switch off without the calibration process being carried out again. The value set at the first start-up is retained.

Basically is it possible that this calibration process is the first calibration process of the sensor arrangement represents that means so that while no offset calibration is carried out during production, since at Use an offset calibration is required and also takes place according to the invention.

In one embodiment of the invention, provision is also made for a basic calibration process to be carried out in the manner of the calibration process when producing the sensor arrangement. The value of the calibration signal determined in the process or a size suitable for generation is stored as a basic calibration value in the sensor signal processing circuit. The basic calibration value is then overwritten by the calibration value during the calibration process ben. Such a basic calibration is particularly advantageous in the case of a digital setting of the calibration signal, in which no negative numbers of the calibration value can be used. The basic calibration value can be saved by a digital number in the middle of the possible number of numbers. Such a digital number then represents the quantity suitable for generating the calibration signal, in that this number generates, for example via a digital / analog converter, a corresponding calibration signal which is added to the sensor signal. If a negative calibration is required, that is to say the calibration value is to be reduced compared to the basic calibration value, the number corresponding to the calibration value is reduced, but still in the positive number range.

Especially is appropriate it that the defined value of the measurand to zero or one value defined as zero value is set. The zero value must be used do not necessarily correspond to the physical zero value of the measured variable. For example, if the sensor consists of a strain gauge, the is attached to an already mechanically pre-stressed component, for its voltage changes to monitor the zero value or its value defined as zero value can be the Measured variable at the beginning of the installation also describe this condition. Definitely is however, it is appropriate to First start-up of the sensor arrangement in the unloaded state of the sensor and the sensor output signal to its zero value or to its zero value to have a defined value set.

In Another embodiment of the method provides that the flag by an external intervention in the sensor signal processing circuit is adjustable to the first value.

By this configuration will make it possible Recalibration to a later one Repeat the time again if, for example, the Sensor had to be removed and reinstalled.

The arrangement-side solution The task is that in the sensor signal processing circuit a non-volatile Flag memory is arranged in which at least one flag can be stored is. This memory enables it, the calibration process according to the invention after querying the flag.

The The invention will be explained in more detail below using an exemplary embodiment. In the associated Character shows:

1 an arrangement of several sensor arrangements on one evaluation device,

2 a sensor arrangement with analog output and a digital implementation of the inventive method and

3 a sensor arrangement with a digital output.

To the in 1 shown evaluation circuit 1 are several sensor arrangements 2 consisting of one sensor each 3 and a sensor signal processing circuit 4 , connected. The sensor arrangement can be connected 2 be made directly to the evaluation circuit, as is the case in the upper part of the evaluation circuit 1 is shown. The other possibility is to connect several sensor arrangements 2 via one through the sensor signal processing circuits 4 trending bus 5 , Finally, there is the possibility of an external bus 6 lead to the outside, on which then several sensor arrangements 2 are arranged. According to the prior art, an offset calibration was required for each individual sensor arrangement 2 in the evaluation circuit 1 to store a calibration value that was previously for each individual sensor arrangement 2 had to be determined. This is avoided by the invention. For this, circuit arrangements are used, as shown in the 2 and 3 are shown.

In the 2 sensor arrangement shown 2 consists of a sensor 3 and a sensor signal processing circuit 4 , In the sensor signal processing circuit 4 is an amplifier 7 arranged, the input side with the sensor signal on the signal line 8th is applied. The output of the amplifier 7 is with an adder 9 connected. The exit 10 of the adder 9 also provides the output of the sensor signal processing circuit 4 represents the sensor output signal. With the exit 10 is an analog / digital converter, in the simplest case a comparator 11 connected. The comparator 11 is on the output side of an evaluation electronics 12 on. The evaluation electronics 12 is with a non-volatile memory 13 connected to a flag store 14 includes. The memory 13 is with a digital / analog converter 15 connected, its analog output 16 also with the adder 9 connected is.

All sensors shown in the exemplary embodiment 3 can represent pressure sensors, for example. Accordingly, these are sensor arrangements 2 offset-calibrated during manufacture such that no pressure is applied to the sensors 3 the sensor output signal at the output 10 Is zero. With the sensor arrangement 2 according to 2 is in memory for this 13 a basic calibration value stored in the form of a digital number. Through the digital / analog converter 15 it becomes an analog voltage value, which together with the output of the amplifier 7 at the adder the sensor output value at the output 10 results.

The flag register is also in production 14 a flag has been set to logic ONE, which means that on the sensor array 2 so far only the basic calibration has been carried out.

Will the sensor 3 now mechanically installed, mechanical installation forces act on it, which generate a permanent installation offset, so that another sensor output signal at the output 10 would be generated even if the sensor 3 would not be pressurized.

To avoid this, the sensor output signal is sent through the comparator 11 rated. As the sensor output signal usually shows a value different from zero and the comparator 11 is set to zero, it will show a logical ONE at its output. This is from the evaluation electronics 12 detected. Furthermore, the evaluation electronics 12 determines that the flag is in the flag store 14 is logically ONE. The evaluation circuit is provided with these two pieces of information 12 so long changed values in memory 13 write until over the digital / analog converter 15 and the adder 9 a sensor output voltage at the output 10 that corresponds to the value zero. This will be the comparator 11 assume the value of a logical ZERO at its output. This stops the evaluation electronics 12 the process of changing the memory content of the memory 13 and sets the flag in the flag memory 14 at logical ZERO. So that is in the memory 13 the numerical value stored, which is the calibration signal at the output 16 for all other applications.

From the flag store 14 is an external flag line 17 led to the outside. About this flag line 17 can the content of the flag memory 14 be changed from the outside. For example, it can be reset to logical ONE. This causes the next time the sensor arrangement is switched on 2 the process begins again, that is, a calibration is carried out again. This is particularly expedient if, for example, the sensor has been removed and reinstalled, since the pressure conditions on the sensor then change 3 will most likely have changed.

The sensor arrangement 2 according to 3 also consists of a sensor 3 and an amplifier 7 , At the output of the amplifier 7 here is an analog / digital converter 18 connected. This provides amplified digital sensor signals to an arithmetic unit at its digital output 20 , To the calculator 20 is also a non-volatile memory 13 with a flag memory 14 connected. If the flag register is now set to logic 1 in the manner shown above, the arithmetic unit stores the memory content in the memory 13 constantly changed until the result of the addition from the signal at the digital output 19 and the content of the memory 13 Results in zero. Then the change in memory content 13 stopped and the flag in the flag memory 14 set to logic ZERO. Then remains in the non-volatile memory 13 the calibration value for the further use of the sensor arrangement 2 consist.

1

evaluation

2

sensor arrangement

3

sensor

4

Sensor signal processing circuit

5

bus

6

external bus

7

amplifier

8th

Sensor signal line

9

adder

10

output

11

comparator

12

evaluation

13

Storage

14

flag memory

15

Digital / analog converter

16

analog output

17

external flag line

19

digital output

20

calculator

Claims (5)

Method for offset calibration of a sensor signal, in which, under the action of a measured variable to be determined, a sensor signal present at the output of a sensor is processed in a sensor signal processing circuit belonging to a sensor arrangement by amplifying it with a gain factor other than zero, applying a calibration signal and outputting it as a sensor output signal , characterized in that during the manufacture of the sensor ( 3 ) in the sensor signal processing circuit ( 4 ) a flag in a non-volatile memory ( 14 ) is set to a first value that when the sensor is started up ( 3 ) the sensor ( 3 ) a defined value of the measured variable is exposed and a calibration process is triggered automatically or manually controlled when the flag has the first value, the value of the calibration signal being changed during the calibration process until a sensor output signal corresponding to the defined value of the measured variable hires and the thereby occurring value of the calibration signal or a variable suitable for generating this value as a calibration value in the sensor signal processing circuit ( 4 ) is stored in a non-volatile manner and the flag is then set to a second value different from the first value. A method according to claim 1, characterized in that in the manufacture of the sensor ( 3 ) a basic calibration process is carried out in the manner of the calibration process and the value of the calibration signal determined in the process or a variable suitable for generation as the basic calibration value in the sensor signal processing circuit ( 4 ) is saved and that the basic calibration value is overwritten by the calibration value. A method according to claim 1 or 2, characterized in that that the defined value of the measured variable is at its zero value or a value defined as zero value is set. Method according to one of claims 1 to 3, characterized in that the flag by external intervention in the sensor signal processing circuit ( 4 ) can be set to the first value. Sensor arrangement with a sensor and a sensor signal processing circuit, which contains an amplifier, a non-volatile calibration value memory and an adding point, characterized in that in the sensor signal processing circuit ( 4 ) a non-volatile flag memory ( 14 ), in which at least one flag can be stored.