WO2006051057A1

WO2006051057A1 - Device and method for compensating transducers

Info

Publication number: WO2006051057A1
Application number: PCT/EP2005/055696
Authority: WO
Inventors: Dietfried Burczyk; Wolfgang Dannhauer; Fred Haker; Andrej Kalendarev; Hans-Jürgen Piersig
Original assignee: Endress+Hauser Gmbh+Co. Kg
Priority date: 2004-11-11
Filing date: 2005-11-02
Publication date: 2006-05-18
Also published as: DE102004054644A1

Abstract

The invention relates to a compensation device for a plurality of transducers for detecting a measured variable. Said transducers generate a measured variable-dependent primary signal that has interference cross-sensitivities and comprise, when used according to the invention, an interference sensor and a correction circuit for processing the primary signal to give a corrected output signal using compensation parameters. The compensation device comprises a plurality of sensor receptacles; a measured variable adjuster for adjusting reference values of the measured variable; an interference adjuster for adjusting various values of the interference value; a data acquisition device for reading out measured data sets of the individual transducers; and a data processing unit for determining the compensation parameters using the read-out measured data sets. The compensation device has a trigger signal output. Every sensor is associated with a data storage having control electronics that are operatively linked with the trigger signal output. After emission of a trigger signal to the trigger signal output, the actual measured data set of the sensor associated therewith is stored in every data memory.

Description

description

Device and method for compensating Meßwert¬ sensors

The present invention relates to a device and a method for compensating transducers.

[0002] Transducers in the sense of the invention can be, for example, transducers of process measuring technology, in particular pressure transducers, flow transducers, fill level transducers, potentio metric transducers, amperometric transducers, photometric transducers, spectrometric transducers and moisture measuring transducers.

Transducers convert a measured variable into a sensor signal, wherein the

Transducer often have a cross-sensitivity to a disturbance. The disturbance may be, for example, a temperature. It is therefore customary to compensate transducers over the range of application of the measured variable and the disturbance variable in order to obtain a sensor signal which is in a defined, preferably proportional, relationship with the measured variable.

The problem underlying the invention will now be explained using the example of pressure transducer, without, however, being restricted thereto. Pressure transducers in the sense of the invention comprise transducers for absolute pressure, relative pressure or differential pressure.

Druckmesswertaufnehmer lead to detect the measured variable pressure a Trans¬ formation of this size in an electrical signal by which is processed by means of a customized for the respective measurement signal processing.

For example, in the case of pressure transducers with a capacitive pressure measuring cell, a pressure-dependent change in capacitance is converted into a pressure-dependent primary electrical signal, which, however, is dependent on interference variables such as temperature.

In Druckmesswertaufnehmer with a piezoresistive pressure measuring cell with a bridge circuit, a pressure-dependent bridge signal is correspondingly converted into a primary signal, which likewise has a pronounced temperature response.

In order to determine the correction terms required to compensate for these disturbances, the primary signal is compared with the actual reference values with respect to zero point and span as well as the characteristic curve at different temperatures and pressure values.

[0009] In the compensation of pressure transducers with analog signal Zero point, gain and linearity of the sensor are compensated by a resistance / thermistor network in the entire operating temperature range of the pressure transducer.

In digital compensation, the coefficients for minimizing the characteristic curves and temperature errors are determined on the basis of the comparison of the measured values with the reference values via a mathematical model with an equation system of the nth order. The coefficients are finally stored in a memory of the sensor electronics. Alternatively, a grid of interpolation points can also be stored, an interpolation calculation taking place between these interpolation points. The coefficients are finally stored in a memory of the sensor electronics. Alternatively, a grid of interpolation points can also be stored, an interpolation calculation taking place between these interpolation points.

Prerequisite for the compensation is a characteristic measurement in the entire temperature range of the sensor, for example -40 ° C to 85 ° C with interpolation points at room temperature and intermediate temperatures such. -10 ° C and 50 ° C.

For this purpose, in the context of series production, batches with a large number of transducers, for example of the order of 100 units each and more, are compensated in a compensation arrangement. For this purpose, the compensation arrangement comprises, for example, a temperature control device for controlling the temperature of the measured value sensors as well as pressure supply lines and electrical connections for each individual sensor.

After reaching the predetermined temperature values, a pressure characteristic is recorded in each case. In the case of transducers with analog signal output, the interrogation of the output signal is carried out by means of a scanner or measuring point selector switch. For transducers with digital signal output via a bus system, each measuring cell being addressed individually. Alternatively, it is also possible for transducers with a digital signal output to address the individual transducers successively with a scanner.

In the sense of a meaningful statistic, one averaged per pressure sensor

Data record recorded the reference pressure, the operating voltage and the Sen¬ sensor signals to pressure and temperature and was averaged over 30 measurements.

The measured value recording takes, for example, in a batch with 120 Meßwert¬ and 30 measurements per record and measuring point about 3 minutes per measurement point for the entire batch. On the one hand, this is disadvantageous with regard to the total duration of the compensation and, on the other hand, it is worth improving for the accuracy of the compensation since it is difficult to keep the predetermined pressure and temperature exactly constant over a period of 3 minutes. The present invention is therefore based on the object, an apparatus and a method for improved compensation of transducers, ins¬ particular Druckmesswertaufnehmer provide.

The object is achieved according to the invention by the device according to the independent patent claim 1 and the method according to the independent patent claim 12.

The inventive compensation device for a variety of

[0019] Transducers for detecting a measured variable, wherein

[0020] the transducers

[0021] In each case, a primary signal dependent on the measured variable generates which transverse sensitivities have an interference variable; and

The compensation device

A plurality of sensor receptacles for receiving transducers;

[0024] a measured variable adjuster for setting reference values of the measured variable to which the transducers are exposed;

A disturbance divider, for setting values of the disturbance to which the transducers are exposed; and

[0026] a data acquisition device for reading out measured data sets of the individual transducers, wherein the measured data sets contain at least one value representing the measured variable;

[0027] comprises;

Characterized in that

The compensation system further comprises a trigger signal output, and

[0030] Each data recorder is assigned a data memory with control electronics, which is operatively connected to the trigger signal output, wherein the current measurement data record of the associated sensor is simultaneously stored in each of the data memory after the output of a trigger signal at the trigger signal output.

The control electronics may in particular comprise a microprocessor.

The data storage device associated with the measuring transducer can be, for example, memory modules, which are each part of the sensor and, if appropriate, are functionally connected to the correction circuit.

Similarly, the data storage associated with the transducer may be components of the compensation device operatively connected to the associated transducers.

If the transducers output analog output signals, each sensor is further associated with an analog / digital converter (ADC), via which the measurement data records are read into the data memory.

The transducers have a certain step of their production Correction circuit, which processes the primary signal on the basis of Kompensations¬ parameters and each detected value of the disturbance and generates a Aus¬ output signal which is to represent the measured variable after compensation regardless of the disturbance, the compensation parameters are determined using the compensation device. For the realization of the invention, however, it is fundamentally irrelevant whether or not the transducers already have the correction circuit in the compensation device during the compensation. In the compensation device according to the invention, only the interfaces to the transducers are to be designed according to the equipment of the transducers.

The transducers likewise each have a disturbance variable sensor for detecting the disturbance variable as of a specific step in their production, since a current value of the disturbance variable is indispensable for processing the primary signal of the measured variable. Here too it is a question of the expediency whether or not the transducers already have the disturbance variable sensor during the compensation in the compensation device. If, for example, the disturbance variable is identical for a given disturbance variable value over the entire compensation device, and the accuracy of disturbance measurement with subsequently installed disturbance sensors is unproblematic, an individual measurement of the disturbance variables at the location of the respective transducer can be dispensed with during the compensation , Accordingly, in this case the incorporation of the interference quantity sensors in the transducers prior to the compensation is not absolutely necessary. If, on the other hand, the value of the disturbance variable on the one hand spatially varies over the Kompensations¬, or if on the other hand have the measurement behavior of Störgrö¬ ßensensoren production-dependent fluctuations, it is advisable if the transducers already have a disturbance variable sensor at the time of compensation in the Kompensations¬ so that its Störgrößen- measured values of the disturbance in the respective measurement data set can be detected.

In a currently preferred embodiment of the invention, the compensation device can furthermore have a data processing unit for determining the compensation parameters on the basis of the read-out measurement data sets. Alternatively, the acquired measurement data sets can be transmitted to a data processing unit separate from the compensation device in order to have the compensation parameter determined by it.

The measured data records can contain, for example, in addition to the value representing the measured variable, a value representing the disturbance variable which was measured by the respective disturbance variable sensor. Further additional parameters, such as, for example, the respective supply voltage, can also be used with the individual ones Measurement data sets are stored in the respective data storage associated with the transducer. The storage of said additional information with the individual transducers is particularly advantageous if a variance of the corresponding variables such as interference value or value of the supply voltage is to be expected via the plurality of transducers via the compensation device.

Similarly, it may be desirable to complete complete

To process records that are sufficient to allow the determination of Kompensati¬ on parameters. In this case, it is advantageous, for example, to store the predefined reference value, if necessary, the disturbance variable value with the measured data record.

Insofar as the data to be read from the plurality of data memories is increased by the additional data, the read-out time increases. In order to avoid this, given variables such as the reference value of the measured variable and the predetermined value of the disturbance variable can also be assigned to the measured data sets at another point or at a different time, for example in the data processing unit when determining the individual compensation parameters for the plurality of Meßwert¬ sensor. The assignment is readily possible, for example, via the identification data of the measurement data record.

The advantage of the invention is twofold. First, the next reference value for the measured variable and / or the next value for the disturbance variable can already be set by the compensation device immediately after the measurement data sets of all transducers of a batch have been recorded and stored synchronously. Meanwhile, the data memories of the individual transducers can be read out without delay for the entire compensation process by means of the data acquisition device sequentially. Secondly, the reference value of the measured variable only has to be kept constant for a short time in order to achieve as uniform boundary conditions as possible for the compensation of all sensor modules.

Details of the mechanical structure of a compensating device can be found, for example, in the unpublished German patent application with the file reference 103 59 866.9.

The inventive method for compensating a batch of Meßwert¬ sensors, which comprises a plurality of transducers, wherein

The transducers each generate a dependent of the measured variable primary signal having cross-sensitivities to a disturbance variable; and

The method comprises the following steps:

Setting a value pair of a reference value of the measured variable and a Disturbance variable value of the disturbance to which the plurality of transducers is exposed;

Simultaneous writing of simultaneously recorded measurement data records from the measurement value receivers into a multiplicity of data memories, one data memory being allocated to each transducer;

Sequential reading of the measurement data sets from the plurality of data memories into a data processing device for determining compensation parameters, and

Wherein the steps are repeated until sufficient

Number of pairs of values from a reference value of the measured variable and a Stör¬ size value of the disturbance measurement data sets have been determined in order to determine the Kompensati on parameters for the plurality of transducers can.

To speed up the process, the sequential readout of the

Measurement data records from the plurality of data memories take place simultaneously with the setting of a new value pair of value pairs of a reference value of the measured variable and a disturbance variable value of the disturbance variable.

The method according to the invention relates in particular to the measuring probes discussed above and can be carried out in particular by means of the compensation device according to the invention.

The invention will now be explained with reference to an exemplary embodiment of a compensating device for pressure measuring sensors shown in the FIGURE. It shows:

FIG. 1 shows a block diagram for illustrating the mode of operation of the device according to the invention; FIG.

The compensating device shown in FIG. 1 comprises a compensating body 1 with N sensor module receptacles. A tempering device 60 serves as a disturbance size divider.

The compensating body 1 is fed by means of the tempering device 60, which comprises a circulating thermostat, with a tempered liquid temperature control medium via Temperiermedienleitungen 65, whereby the temperature of the Kompensati¬ onskörpers can be set to values between -40 ° C and 200 ° C exactly. The circulating thermostat has in the described embodiment, a heating power of 3kW and a cooling capacity of about 1 kW.

Cylindrical pressure transducers, which are inserted into the sensor receptacles of the compensation body 1, do not come into direct contact with the temperature control medium. Instead, by means of a close thermal coupling between the sensor modules and the compensation body, the comparatively low thermal mass of the sensor modules and an adequate guidance of the tempering liquid in the compensation body, a tempering of the sensor modules in a minute is achieved. scored. For example, a temperature change from 80 C to - 20 C within 15 min is possible.

The temperature control device 60 is controlled by a central control unit 50 which communicates with the temperature control device via a data bus, for example an IEEE 488 data bus. It can be approached any number of temperature levels, what u. a. a compensation of higher orders allowed.

The N sensor receptacles can be supplied to a programmable pressure regulator 70 with a pressure which is required for characteristic curve measurement at the most varied temperatures for the sensor modules. The pressure regulator 70 is also controlled by the central control unit 50. The pressure regulator serves as a reference value adjuster to this extent.

Instead of the arrangement described, any conventional temperature cabinets with suitable pressure actuators can also be used.

Furthermore, the device according to the invention comprises means 51 for the computer-aided archiving of the measurement data in a database system, so that by means of this data arbitrary report and product-specific protocols can be created. In addition, continuous process control via statistical methods is possible.

The pressure transducers comprise, in addition to a pressure measuring cell and a temperature sensor, an integrated circuit board with an ASIC, as well as a standard interface to customer-specific functional electronics, for example for voltage, current, switching functions and data exchange. The circuit board is u. a. the uniform electrical contact during the compensation process.

The transducers have on the printed circuit board a writable memory element, e.g. an EEPROM or a flash memory, wherein the writable memory element can be integrated into a microcontroller. In the memory element, after the compensation has been carried out, the determined compensation parameters, e.g. Coefficients for a polynomial compensation model filed.

The communication between the pressure transducers and the

Control unit can be done, for example via the data bus 55, and a scanner 80 with an ASIC interface, the latter reads out measurement data sets.

After setting a pressure-temperature value pair, a trigger signal is output to each sensor via the data bus, whereupon the simultaneous pressure and temperature measurement and the simultaneous recording of the measurement data records in the respective memory elements of the transducers takes place. Subsequently, the scanner 80 scans interface lines 82 to the sensor modules in succession and reads out the measurement records sequentially. The measured data records comprise the pressure measured by the pressure transducer, the temperature at the location of the pressure measurement value. sensor, which was measured with the internal temperature sensor of the pressure sensor. The reference pressure value is assigned in a currently preferred embodiment, the retrieved measurement data only later. Similarly, the measured data set can subsequently be assigned a temperature value, which was measured in the compensation body, as the reference value, in order to calibrate the internal temperature sensor of the individual pressure transducers in each case.

Claims

claims

Compensation device for a variety of transducers for

Detecting a measured variable, wherein the transducers each generate a dependent of the measured variable primary signal which has cross sensitivities to a disturbance variable; wherein the compensation device comprises: a plurality of sensor receptacles for receiving a multiplicity of measured value pickups; a measurement quantity adjuster for setting reference values of the measured variable to which the transducers are exposed; a Störgrö¬ ßensteiler, for setting different values of the disturbance to which the transducers are exposed; a data acquisition device for reading out measured data sets of the individual transducers, wherein the measured data sets contain at least one value representing the measured variable; and characterized in that the compensation system has a trigger signal output, and each sensor is assigned a data memory with control electronics which is operatively connected to the trigger signal output, wherein after the output of a trigger signal at the trigger signal output the current measurement data record of the associated sensor is stored.

Compensation device according to claim 1, wherein the transducers each having a Störgrößenensensor for detecting the disturbance.

[0003] Compensation device according to claim 1 or 2, wherein the Transducer have each a correction circuit which processes the primary signal based on compensation parameters and the detected value of the disturbance and generates an output signal that represents the measured variable after compensation regardless of the disturbance.

[0004] Compensation device according to one of claims 1 to 3, wherein the compensation device further comprises a data processing unit for determining the compensation parameters on the basis of the read-out measurement data sets.

Compensation device according to one of claims 1 to 4, wherein the

Transducer have analog output signals, and each sensor further an analog / digital converter (ADC) is assigned, via which the measurement data sets can be read into the data memory.

[0006] Compensation device according to one of claims 1 to 4, compensation device according to claim 1, wherein the data memory associated with the transducers are memory modules of the transducers integrated in the transducers. Compensation device according to claim 3 and 6, wherein the memory modules are functionally connected to the correction circuit.

Compensation device according to one of claims 1 to 5, wherein the

Data memory associated with measuring sensors are components of the compensation device which can be connected to the transducers.

Compensation device according to claim 2 or one dependent thereon

Claim, wherein the measurement data sets in addition to a value representative of the measured value, a value representing the disturbance value, which was measured by the respective disturbance variable sensor of a transducer.

[0010] Compensation device according to one of the preceding claims, wherein the measured data sets contain an externally measured disturbance variable value and / or a reference value of the measured variable and / or the respective supply voltage of the measuring transducer.

A method for compensating a batch of transducers, which comprises a plurality of transducers, in particular with a device according to one of the preceding claims, wherein each of the transducers generates a dependent on the measured variable primary signal having cross sensitivities to a disturbance, and the method The following steps include: setting a value pair of a reference value of the measured variable and a disturbance variable value of the disturbance variable to which the transducers are exposed; simultaneous writing of simultaneously acquired measurement data sets from the transducers into a multiplicity of data memories, one data memory being allocated to each transducer; sequential readout of the measurement data sets from the plurality of data memories into a data processing device for determining the compensation parameters, the steps being carried out repeatedly until measurement data sets have been determined for a sufficient number of value pairs from a reference value of the measured variable and a disturbance variable value of the disturbance variable to determine compensation parameters for the plurality of Meßwert¬ be able to determine.

The method according to claim 11, wherein the sequential readout of the measured data sets from the plurality of data memories takes place simultaneously with the setting of a new value pair of value pairs of a reference value of the measured variable and a disturbance variable value of the disturbance variable.