WO2008052377A2 - Method and measuring system for measuring a physical quantity - Google Patents

Method and measuring system for measuring a physical quantity Download PDF

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Publication number
WO2008052377A2
WO2008052377A2 PCT/CH2007/000534 CH2007000534W WO2008052377A2 WO 2008052377 A2 WO2008052377 A2 WO 2008052377A2 CH 2007000534 W CH2007000534 W CH 2007000534W WO 2008052377 A2 WO2008052377 A2 WO 2008052377A2
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WO
WIPO (PCT)
Prior art keywords
signal
measuring
reference
reference signal
signal input
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Application number
PCT/CH2007/000534
Other languages
German (de)
French (fr)
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WO2008052377A3 (en
Inventor
Lars Kamm
Werner Hinn
Roman Baumann
Original Assignee
Hsr Hochschule Für Technik Rapperswil
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Priority to CH17402006A priority Critical patent/CH698811B1/en
Priority to CH1740/06 priority
Application filed by Hsr Hochschule Für Technik Rapperswil filed Critical Hsr Hochschule Für Technik Rapperswil
Publication of WO2008052377A2 publication Critical patent/WO2008052377A2/en
Publication of WO2008052377A3 publication Critical patent/WO2008052377A3/en

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01DMEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D18/00Testing or calibrating of apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
    • G01D18/008Testing or calibrating of apparatus or arrangements provided for in groups G01D1/00 - G01D15/00 with calibration coefficients stored in memory
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01DMEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D3/00Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
    • G01D3/028Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure
    • G01D3/036Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure on measuring arrangements themselves
    • G01D3/0365Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure on measuring arrangements themselves the undesired influence being measured using a separate sensor, which produces an influence related signal

Abstract

The invention relates to a method for measuring a physical quantity by means of a measuring system comprising a measuring sensor, a signal source and a computation unit, wherein the computation unit has a reference signal input, a measurement signal input and a signal output and generates an amplified difference between a measurement signal and a reference signal as output signal. In the method, a reference signal is applied both to the reference signal input and to the measurement signal input of the computation unit, an offset error of the measuring system is determined from the resultant output signal of the computation unit, an attenuated reference signal is applied to the reference signal input and the reference signal is applied to the measurement signal input and an actual gain quantity is determined by the difference between the then resultant output signal of the computation unit and the previously calculated offset error, then the reference signal is applied to the reference signal input and a measurement signal is applied to the measurement signal input and a corrected output signal is determined by forming the difference between the resultant output signal of the computation unit and the offset error and the actual gain quantity is compared with a predetermined desired gain quantity and a total gain of the measuring system is reduced if the actual gain quantity is greater than the desired gain quantity, or increased if the desired gain quantity is greater than the actual gain quantity. The invention furthermore relates to a measuring system for carrying out such a method.

Description

The method and measuring system for measuring a physical quantity

REFERENCE TO RELATED APPLICATIONS

This application claims priority of the Swiss patent application no. 1740/06, which was filed on November 2, 2006, the entire disclosure of which is hereby incorporated by reference.

technical field

The invention relates to a method for

Measuring a physical value according to the preamble of claim 1 and a measurement system for carrying out such a method according to the preamble of claim 7.

State of the art

Known measuring systems with which even small changes in amplitude physical variables can be captured, typically have high gains in the order of 10 '000 or more. Such measurement systems are typically used when the absolute change in the amplitude of a measurement signal, which is an alternating signal against a known amplitude of the same frequency reference signal to be determined. With such large gain factors smallest component tolerances contained in the measuring systems components often produce significant offset and gain error, the offset and gain errors are temperature-dependent in general. The measurement systems comprise resistive, inductive or capacitive sensors, which are operated with alternating current, typically two identical sensors are used, one of which serves as a measuring sensor and a reference sensor.

Such a measurement system is shown in FIG. 1 The measuring system 1 comprises a measuring sensor 2, a reference sensor 3, and a computation unit 4. The computation unit 4 comprises a signal source 5, which supplies the measuring sensor 2 and the reference sensor 3 with an alternating voltage V 3 of the frequency f s. The reference sensor 3 is subjected to a constant reference physical size, for example a constant pressure, a constant way or a material having a dielectric constant, and outputs a

Reference signal V ref from a reference signal input of the calculation unit 6. 4 The measuring sensor 2 is exposed to the physical value to be measured and outputs a measurement signal V be measured to a measuring signal input 7 of the calculating unit 4 from. The amplitude V i of the measured amp

Measuring signal V me ss, which is supplied by the measuring sensor 2, depends on the physical quantity to be measured. The amplitude of a V ref of the reference signal V m pi rβf which is output from the reference sensor 3 is constant. In an error-free measuring system 1, the calculating unit 4 forms an amplified difference of the amplitude values ​​of the measurement signal and the reference signal in accordance with

V ou t = G (V me ss_ainpl ~ Vref_ampl) ■

where G is the gain of the error-free operating calculating unit 4, V measured _ amp i is the amplitude of the measurement signal V re f_ a πipi the amplitude of the reference signal and V out which is applied to a signal output 8 of the computation unit 4 output signal. Environmental influences such as temperature and humidity, which act equally on the measuring sensor 2 and the reference sensor 3 are typically eliminated by difference formation in the measuring system 1 or in the calculation unit. 4 The above equation for calculating the output signal V out of the measuring system 1 is for an ideal, error-free working measuring system 1. In a real measurement system, however, typically occurs an offset error, which is in particular (for an alternating-current offset error and AC offset error or AC OS error called) is on. This manifests itself typically in that either the measuring signal or reference signal an error signal in the form of an error AC voltage having an amplitude V i acos _ar aP is added. The error signal typically has the same

Frequency as the measuring signal and the reference signal. The offset error can for example be due to the partial gains in the reference signal and the measurement signal associated with passages of the measuring system 1 or the calculating unit 4 are different or that a crosstalk from the effected a channel in the other channel. Further, the offset error may also be due to the temperature dependence of components or components of parameters of the measuring system 1 or the calculating unit. 4

Typically, in real measuring systems, the gain and the gain G is not an absolute constant, but also of parameter variations of the components used in the measuring system 1 and of the temperature dependencies of these parameters dependent. The diseases caused by these dependencies variations in gain are referred to as the gain error.

For a real measurement system 1, that is, for a measuring system 1, which is subject to an offset error and a gain error, the output signal of the measurement system 1 or the calculating unit 4 results in accordance with the following equation:

V 0 Ut - gG (V measured _ a mpi - V ref + V f_ampl aC os_ampl) t

where g represents the gain error factor that is typically between 0.95 and 1.05 and specifies V aC OS_a m pi the offset error, which is formed by the amplitude of the error caused by the offset AC voltage.

Summary of the Invention

It is an object of the present invention

to provide methods for measuring a physical and a measuring system for performing a method for measuring a physical value, with which the influence of offset errors and gain errors on the measurement result can be reduced.

This object is achieved by a method for measuring a physical quantity comprising the features of claim 1 and by a measuring system having the features of claim 7. The inventive method for measuring a physical means of a measuring system comprising a measuring sensor, a signal source and a calculation unit, wherein the calculation unit comprises a reference signal input, a measuring signal input and a signal output and producing as an output an amplified difference of a measurement signal and a reference signal flags, by the steps that a reference signal is applied to both the reference signal input and at the measuring signal input of the computing unit, that from the resulting output signal of the computing unit, an offset error of the measuring system it is determined that the reference signal input terminal an attenuated reference signal, and at the measuring signal input, the reference signal is applied, and determines a Istverstärkungsgrösse by the difference from the now resulting output signal of the calculation unit and the previously calculated offset error that now the REFERENCED zsignal applied to the reference signal input and a measuring signal at the measuring signal input, and a corrected output signal by forming the difference is determined from the resulting output signal of the calculation unit and the offset error is that now after the Istverstärkungsgrösse specified, this is compared with a predetermined desired gain size and an overall gain reducing the measurement system when the Istverstärkungsgrösse greater than the

is required gain size, or is increased when the required gain size is greater than the Istverstärkungsgrösse.

The predetermined desired gain size can be stored by the manufacturer or by the user, for example, in the measurement system, in particular in the calculation unit. The aforementioned steps are repeated, which advantageously leads to a minimization or elimination of a gain error of the measurement system. Is the gain error is eliminated, so the total gain can be kept constant, that is "frozen". Preferably, the aforementioned steps will still pass through all, so that time-variable in setting the overall gain

can be taken into account temperature influences and continuously corrected out. The comparison of the Istverstärkungsgrösse with the predetermined desired gain size can already take place before the application of the measuring signal at the measuring signal input in the inventive method. The overall gain can be reduced or increased by varying the amplitude of the signal source, by changing the gains of a measuring sensor and a reference sensor with the same factor and / or by changing a gain calculating unit. This list is not exhaustive.

The inventive measuring system comprises a measuring sensor, a signal source for supplying power to the measuring sensor, a calculation unit, which is provided with a reference signal input, a measuring signal input, a signal output and an amplifier and is configured such that it during operation of the appended at the reference signal input and at the measuring signal input signals an amplified difference determined. Further, a reference multiplexer that the

Reference signal input is connected upstream, and a measurement multiplexer, which is connected upstream of the measuring signal input, provided, of the reference multiplexer, a reference signal and an attenuated reference signal and of the measurement multiplexer, a reference signal and a

Measuring signal can be output. The reference multiplexer is preferably a signal attenuator upstream of which can provide an attenuated reference signal to the reference multiplexer which in turn can be output by this and bears at its output.

For controlling the calculating unit, the signal source, the reference multiplexer and / or a microcontroller Messmultiplexers is preferably provided. The inventive method and the inventive measuring system when measuring a physical offset error and gain error of a measuring system can be taken into account and corrected out. This makes an accurate measuring a physical is possible. Brief Description of Drawings

Further advantageous embodiments of the invention emerge from the subclaims and the embodiments described below with reference to the drawings. Show it:

Figure 1 is a schematic representation of a measurement system without error correction,

2 shows a block diagram of a measurement system without error correction,

Figure 3 is a graphical representation of time characteristics of in the measurement system of Figure 2 occurring signals,

Figure 4 is a graph of measured in a typical implementation of offset error as a function of temperature,

Figure 5 is a graph of measured in a typical implementation gain error as a function of temperature, Figure 6 is a schematic representation of an inventive measuring system,

Figure 7 is a flowchart for illustrating the inventive method,

Figure 8 is a block diagram of the regulation of the overall gain and

Figure 9 is a graphical representation of the temporal behavior occurring in the block diagram of Figure 8 Great.

In the figures, like reference numerals denote structurally or functionally equivalent components. WAY (S) OF EMBODYING THE INVENTION

Figure 1 is already in the

Introductory described, is being referred here.

Figure 2 shows a block diagram of a measuring system 1 with a measuring sensor 2, a reference sensor 3 and a computation unit 4. The computation unit 4 comprises a signal source 5, which emits an alternating signal V 3 at a frequency f s. The signal source 5 is supplied via corresponding unspecified lines the signal sensor 2 and the reference sensor 3 with the alternating signal V. 3 The reference sensor 3 is subjected to a constant reference physical size, and outputs at its output a reference signal V ref to the frequency f s to the reference signal input 6, the calculating unit 4 from. The measuring sensor 2 is exposed to the physical value to be measured and provides a measurement signal V measured with the frequency f s at the measuring signal input of the calculation unit 7. 4

The calculation unit 4 further comprises a first multiplexer 19 and a second multiplexer 20th The multiplexers 19, 20 each have three inputs, of two abut the reference signal and the measurement signal of the inputs, while at the third input a switching signal V t with a switching frequency f t, which is also referred to as a toggle frequency is applied. The switching signal is generated by a signal generator 18th The multiplexers 19, 20 turn with the switching frequency ft from the reference signal to the measuring signal or of the measurement signal to the reference signal, so that on the one output each of the multiplexers 19, 20, the reference signal or the measuring signal is present either. The multiplexers 19, 20 are designed such or are driven in such switching on the V t that when the output of the first multiplexer 19, the reference signal present at the output of the second multiplexer 20 is applied, the measuring signal and vice versa. The switching frequency f t is preferably chosen much lower than the signal frequency f s. For example, the signal frequency fs is 300 kHz, while the ümschaltfrequenz f t is 1 kHz.

The calculation unit 4 further comprises a subtracter 9, which forms the difference from the output signals of the multiplexers 19, 20th That is, the output signal of the subtraction element 9 corresponds to the difference between the reference signal and the measuring signal and the measuring signal and the reference signal.

The output of the subtractor 9 is multiplied in a multiplier 10 (so-called multiplier) with a square-wave signal having the frequency f s. The rectangular signal is preferably formed by a clipper circuit 11 (a so-called limiter) either from the generated from the reference sensor 3 reference signal or from the signal supplied by the signal source 5 signal. There are provided corresponding unspecified lines connecting the clipper circuit 11 to the signal source 5, the output of the reference sensor 3 and the multiplier 10th In the unspecified lines to the signal source 5 and to the output of the reference sensor 3 switches 12, 13 are provided, one of which is closed and the other is opened so that at the input of clipper circuit 11 is either the reference signal or the signal of the signal source .5 applied. Is the square wave signal from the signal of the signal source 5 generates, it is preferably ensured by a phase shifter 14, that the square-wave signal having the same phase position as the reference signal. For this purpose, in the non-descript line from the signal source 5 to the clipper 11, a phase shifter 14 (so-called phase shifter) is preferably provided.

The calculation unit 4 further comprises a low-pass filter 15, a high pass filter 16 and an amplifier 17th The output signal of the multiplier MPY V 10 is filtered in the low pass filter 15 so that high-frequency signal components and signal components with frequency 2 f s can be suppressed. The low pass filter 15 is preferably designed such that its output value V L p contains only signal components whose frequency is less than or equal to five times the switching frequency f t, so that a square-wave signal of the frequency ft can be reproduced undistorted substantially. The output signal V LP of the low pass filter 15 is then filtered in the high pass filter 16 in order to suppress DC components and DC offset problems (DC offset problems) in which the high-pass filter 16 nachgestalteten amplifier 17 to be avoided. To the amplifier 17, the output of the high pass filter 16 is amplified. The output signal V out of the amplifier 17 constitutes the output signal of the measurement system 1 or the output at the signal output 8 of the computation unit 4 signal. The amplifier 17 may also between the

Subtractor be disposed 9 and the multiplier 10 degrees. However, this would cause the amplifier 17 may have to be designed with broader, than when it is downstream of the low-pass filter 15, since the output signal of the subtractor 9 is still

Contains signal components at the frequency f s, which can be suppressed only by the action of the multiplier 10 and the low pass filter 15 °.

The multiplier 10 has the effect of a synchronous rectifier, so that a good linearity of the rectification process is ensured. The measuring system 1 shown in the figure 2 illustrates a so-called lock-in amplifier, which is characterized in that its filter characteristics being such that interference signals having a different frequency than the signal frequency f s and odd multiples thereof, well-suppressed , Also the noise frequency f s and odd multiples thereof can be suppressed advantageously if their phase differs from the phase of the square wave signal generated by the amplitude limiter. 11 Even very noisy, from the

Measuring sensor 2 measuring signals delivered can thus be implemented in substantially noise-free output signals V out.

Figure 3 shows exemplary waveforms of signals in the example shown in Figure 2 the measuring system. The measuring sensor 2 and the reference sensor 3 preferably provide voltages as an output signal so that it preferably is in the illustrated in the Figure 3 waveforms to voltage curves. On the abscissa of the coordinate systems a) shown in FIG 3 to f) the time is indicated.

In the coordinate system a) the switching signal V t. The switching signal is a square wave with the

Switching frequency f t. In the coordinate systems b) and c), the multiplexer outputs V mux i, V MUX2, the multiplexer 19, shown 20th The multiplexer outputs V mux i, V MUX2 each switch V t of the reference signal to the measuring signal or of the measurement signal to the reference signal, after a half-period of the switching signal with the simplicity of illustration, the frequency f s of the measuring signal and the reference signal equal to four times the switching frequency f t is selected, while, in practice, preferably equal to 300 times the switching frequency f t is selected. In the coordinate system d) the output of the subtractor 9 is shown, which by the difference V mux i - V is formed mU χ. 2 In the coordinate system e) the output signal V M pγ of the multiplier 10 and the output signal V 1 of P are

Low-pass filter 15 shown. The output signal V L p of the low pass filter 15 is the filtered by the low pass filter 15 output signal V MPY of the multiplier 10. The parameters of the lowpass filter 15 are selected such that the output signal V LP of the low pass filter 15 is a substantially rectangular signal having the frequency is ft. In the coordinate system f) which is connected to the amplifier 17 amplified output signal V LP of the low pass filter 15, which was preferably additionally filtered by the high pass filter 16, is shown. When the output signal V out of the amplifier 17 also is a substantially rectangular signal having the frequency f t with respect to the low-pass filter output signal V LP larger size amplitude. The peak-peak amplitude V p of the outp

Output signal V out of the amplifier 17 is defined as twice the amplitude of the output signal V out and is proportional to the difference between the measured amplitude V _ampi of the measuring signal and the amplitude V ref _ on the pi of the reference signal that is

Voutpp = 2 G (V me ~ V ss_ampl re f_ampl) r

wherein G represents the gain of amplifier 17th The peak-peak amplitude V p P out is preferably digitized via an analog / digital converter and a microcontroller with determined numerically. The analog / digital converter can be integrated in the microcontroller.

In a real measurement system typically temperature dependent AC-Off setfehler and arise

Gain error which may fall at a high overall gain of the measurement system more significant and lead to a distortion of the output signal V ou t. In an ideal measurement system, the peak-peak amplitude V should outpp have the value 0 when the amplitude Vm is e ss_ainpi the measurement signal equal to the amplitude V of the reference signal re f_ampi. In a real measurement system, however, typically occur temperature-dependent offset error V AC acos (also called V offs e t), so that

V O = utpp vacos

is. Figure 4 shows the typical curve of a

Offset error V Acos in function of the temperature T, the temperature T are shown on the abscissa and the offset error Acos V on the ordinate.

In an ideal measurement system is further at a constant difference between the amplitude V of the MES s ampi

Measurement signal and the amplitude V re f on the pi of the reference signal, the output signal V out is also a certain constant value.

In a real measurement system, however, result in gain errors that cause the

Output signal V out at a constant difference between the amplitude V mes s_ampi and the amplitude V ref _ amp i is not constant, but varies with the particular temperature. Figure 5 shows a typical curve of the gain error as a function of temperature, wherein the temperature T on the abscissa and the percentage gain error factor G r e Fe hi are given on the ordinate. In the figure 5, two curves are shown, where the curve with the lower-frequency signal component corresponding to the mean value of the waveform with the higher-frequency signal component.

Figure 6 shows a block diagram of an inventive measuring system 21, which comprises a measuring sensor 3, a reference sensor 2 and a calculation unit 22nd The calculation unit 22 is preferably according to the calculation unit 4 (see Figure 2) configured.

The calculation unit 22 has a

Signal source 5 for outputting a signal V s with a frequency f s, a reference signal input 6, a

Measuring signal input 7 and a signal output 8. The signal source 5 can also be provided outside the calculation unit 22nd The reference signal input 6 is a reference multiplexer 23, and is connected upstream of the measuring signal input 7, a

upstream measuring multiplexer 24th The multiplexers 23, 24 each have three signal inputs and a signal output, which are unspecified. Two signal inputs of the reference multiplexer 23 are connected to the output of the reference sensor 2, wherein between the reference sensor 2 and one of the signal inputs of the reference multiplexer 23, a signal attenuator is connected in 25, so 23 abuts the connected to the signal attenuator 25 signal input of the reference multiplexer an attenuated reference signal.

One of the inputs of the Messmultiplexers 24 is connected to the output of the measurement sensor 3, while another input of the Messmultiplexers 24 is connected to the output of the reference sensor. 2 The multiplexers 23, 24 and / or the signal attenuator 25 may also be arranged within the calculation unit 22nd

It is a microcontroller 26 is provided, which via control signals S 0 and S x, the multiplexers 23, 24 activates. With the control signal Si is the

Microcontroller 26 to the reference multiplexer 23 before, whether present at the output of the reference signal or the attenuated reference signal. With the control signal the microcontroller 26 indicates to the measurement multiplexer 24, whether the reference signal or the measuring signal should be present at its output. Further, the gain of the calculating unit 22 can be specified by the microcontroller 26th

The calculating unit 22 preferably corresponds to the position shown in Figure 2 calculating unit 4, are provided in the two multiplexers 19, 20 (see Figure 2). The microcontroller 26 preferably generates a control signal s t, t which the switching signal V with the frequency configured in the calculation unit 22 and 4 provided multiplexer 19 ft for driving according to FIG 2, 20 is used.

There is preferably provided an analog / digital converter 27, the output signal V out of the calculation unit 22 and digitized the measuring system 21st The numerical value of the peak-to-peak amplitude of the output signal Voutpp V ou t can be calculated in the microcontroller 26 and stored in a register of the microcontroller 26th The analog / digital converter 27 is preferably integrated into the microcontroller 26th

The microcontroller 26 preferably performs the inventive method described below in reference to Figure 7 by, corrects the output signal V out of offset and gain errors, and provides the corrected output signal then preferably digital, for example via a serial port is available.

Figure 7 shows a flow chart of the inventive method. After the start of the inventive method, the reference multiplexer 23 and the measurement multiplexer 24 (see Figure 6) such as and Si driven by the control signals from the microcontroller 26 in a first method step 30 which is used to determine the offset error, that both at the output of

Reference multiplexer 23 is applied as the reference signal also at the output of Messmultiplexers 24th The control signals Si and so the microcontroller 26 in this case have the value 1. The output of the reference multiplexer

23 is connected to the reference signal input 6 and the output of Messmultiplexers 24 is connected to the measuring signal input of the calculation unit 7 22nd both at

Reference signal input 6 and at the measuring signal input 7 of the calculating unit 22 is therefore the reference signal and the signal output 8 of the calculating unit 22 gives the output signal to

V 0 = Ut gGVacos = gG (v ref v + acos - v rβf)

wherein V rβf the reference signal V acos the offset error, the gain error factor g and G correspond to the gain calculating unit 22nd The resulting

Output signal V out is proportional to the offset error acos V and is referred to as the offset signal. In an ideal measurement system 21, the offset signal would have a value of 0. The value obtained for the offset signal is preferably stored in a register D 0 of the microcontroller 26th

In a second method step 31 which is used to determine a Istverstärkung of the measuring system, the microcontroller 26 controls the reference multiplexer 23 in such a manner that the attenuated reference signal ref aV is present at its output. For this purpose, the control signal Si has the value 0. The multiplexer measurement

24, the microcontroller 26 controls to continue such that the reference signal V rβf present at its output. The control signal So has for this purpose the value 1. At the signal output 8 of the calculation unit 22 and the measuring system 21 results in the following output signal

V 0 = Ut gG (V ref - aV ref) + = gGVacos CDR ref (l - a) + gGVacos,

where a corresponds to the attenuation factor of the Signalabschwächers 25 and is preferably less than 1. The value obtained for the output signal V out is preferably stored in a register of the microcontroller Di 26th

In a third method step 32, which is used for offset correction of the output signal obtained in the second step 31 and the determination of the Istverstärkung of the measuring system, the difference is formed from the data stored in the registers Di and D 0 values, ie of the formed in the process step 31, the output signal V out = CDR rβf (l - a) + CDR aco s is the

Offset signal GGv acos deducted. As Istverstärkungsgrösse the value results

CDR r ef (1 - a),

the vorgzugsweise in a register D is the microcontroller is stored 26th In this way, a correction of the output value determined in step 32 to the off or setfehler to the offset signal has occurred.

Finally, in a fourth

Step 33, the measuring sensor measurement in which the microcontroller 26 erenzmultiplexer 23 drives the ref, such that the reference signal V Ee at its output: abuts E, and the measurement multiplexer 24 so controls that the measuring signal V meas is present at its output. Thus, the reference signal V re f and at the measuring signal input 7 lie on the measuring signal V measured at the reference signal input. 6 At the signal output 8 results in the output signal

Vout = gG (VMeas ~ V re f + acos V)

whose value is preferably stored in the register of the microcontroller Di 26th This value is now in a fifth

Step 34 corrected by an offset error by the D 0 in the register stored value of the offset signal is subtracted from it. The thus-corrected output signal V r outkor results to be

V o ut corr = gG (V mess - V re f + V acos) - CDR ac0Ξ = gG (V mes s ~ V re f) •

The value out corr determined for the corrected output signal V is preferably stored in a register D measurement of the microcontroller 26 and is accessible from there, for example, via a serial interface.

The corrected output signal V out corr initially a gain error (in the equations taken into account by the gain error factor g) afflicted. This is eliminated iteratively below. To this end, in a sixth method step 35 deposited Istverstärkungsgrösse which is compared with a predetermined desired gain size in the register D, which is for example stored in a register D n of the microcontroller 26th If there is no gain error exists, ie

Gain error factor g has the value 1, corresponding to the Istverstärkungsgrösse the required gain size. If it is determined in the step 35, however, that the Istverstärkungsgrösse is larger than the required gain size, it is in a

Step 36 reduces the overall gain of the measurement system 21st If it is determined in the step 35 that the Istverstärkungsgrösse is less than the required gain size, then in a step 37, the overall gain of the is

Measurement system 21 increases. By increasing or by reducing the overall gain of the measurement system 21, the method steps 30 to 35 and 36 and 37 repeated. Repeated carrying out the procedural steps can take place until the Istverstärkungsgrösse the required gain size corresponds. Then, the overall gain of the Messsysteins 21 can be kept constant. However, gain errors that may occur due to time-varying temperature conditions, continuously to auskorrigieren, the process steps 30 to 35 and 36 or 37 is preferably repeatedly performed.

The overall gain of the measurement system 21 can preferably changed, ie, reduced or increased, that, in particular by means of the microcontroller 26, the gain G of the

Calculation unit is reduced or increased 22nd Alternatively or additionally, the amplitude of the signal supplied from the signal source 5 signal V s, for example, be varied by means of the microcontroller 26 also. Further alternatively or additionally, a

Gain of the multiplier 10, the calculating unit 22 and 4, respectively (see FIGS. 6 and 2) are increased or reduced. Again, this can be done by the microcontroller 26th Further, adjustable amplifiers or attenuators in corresponding positions in the measuring system 21 can additionally be provided, for example within a the measuring sensor 3 associated electronics. Also, the overall gain of the measurement system 21 can be controlled 27 by changing a reference voltage of the analog / digital converter.

Figure 8 shows a schematic diagram of a scheme for correcting the gain error. The controlled system is formed by the measurement system 21 (see Figure 6). acts on the controlled system 21 is a disturbance variable, for example, a sudden

Temperature change, a. The output of the measuring system 21 is formed by the Istverstärkungsgrösse and to a node 40, a target value-actual value comparison takes place, wherein the target value are formed by the required gain size and the actual value by the Istverstärkungsgrösse. The difference determined at the linking point 40 of target value and actual value is fed to a quantizer 41, is determined by means of which the output value of the value of the gain controlled variable at the transition from step 35 to step 30 via step 36 or 37 (see FIG. 7). The output value of the quantizer 41 is applied to an integrator 42 whose output variable represents the gain control variable for adjusting the overall gain of the control system or the measuring system 21st By the provision of the integrator 42 stationary deviations can

Setpoint and actual value, that can be avoided by Istverstärkungsgrösse and should gain size.

Figure 9 illustrates the waveforms of occurring in the block diagram of Figure 8 signals or large scale. The coordinate system g) shows the time course of the disturbance variable, wherein at the time ti a disturbance step, for example, a jump in temperature takes place. Coordinate system h) shows the course of Istverstärkungsgrösse, which (on a required gain size target value) is adjusted. After the abrupt change of the disturbance variable at the time ti, a regulation of the Istverstärkungsgrösse takes place after a brief drop in Istverstärkungsgrösse turn on the required gain size, that is, the disturbance variable is compensated. in the

Coordinate system i) the variation of the gain control variable is illustrated. During the initial adjustment of Istverstärkungsgrösse to the desired value or the desired gain size, the gain control variable changes until the desired degree of amplification is reached. After that, she oscillates around a constant mean, if the control process is not stopped and the gain size is frozen. At time t the Störgrössensprungs the gain control variable starts to move again until the

Gain control variable has again reached its target value. While in the present application, preferred versions and embodiments of the invention are described, it is distinctly understood that the invention is not limited in this way and may be practiced in other ways within the scope of the following claims.

Claims

claims
1. A method for measuring a physical means of a measuring system (21) comprising a measuring sensor (3), a signal source (5) and a calculation unit (22) having a reference signal input (6), a measurement signal input (7) and a signal output (8) has, wherein the calculation unit (22) as an output signal (V ou t) is an amplified difference of a measurement signal (V meas) and a reference signal (V ref) produced, characterized by the following steps: a) applying a reference signal (V ref f) both (at the reference signal input 6) and to the
Measurement signal input (7) of the calculation unit (22), b) determining a signal offset of the measurement system (21) by the output signal (V out) of the calculation unit (22), c) applying an attenuated
Reference signal (AV REF) to the reference signal input (6) and the reference signal (V Eef) to the measurement signal input (7), d) determining a Istverstärkungsgrösse by the difference from the output signal (V ou t) of
Calculation unit (22) and the offset signal, e) applying the reference signal (V re f) at the reference signal input (6) and a measurement signal (V meas) to the measurement signal input (7), f) determining a corrected
Output signal (V ou t k orr) by forming the difference from the output signal (V ou t) of the calculation unit (22) and the offset signal, g) comparing the Istverstärkungsgrösse with a predetermined desired gain size, h) reducing a total gain of the measuring system (21), when the Istverstärkungsgrösse is larger than the required gain size and increasing the total gain when the required gain size is greater than the Istverstärkungsgrösse. i) repeating steps a) to h).
2. The method according to claim 1, characterized in that the overall gain of a by changing the amplitude of the signal source (5), by changing the gains of the measuring sensor (3) and a reference sensor (2) with the same factor and a and / or by changing is reduced gain calculation unit (22) or raised.
3. The method of claim 1 or 2, further characterized in that the difference applied from a at the measuring signal input (7) signal and applied to a the reference signal input (6) signal is multiplied by a square wave signal whose frequency is the frequency of the reference signal input (6) or on the measuring signal output (7) applied signal corresponds.
4. The method of claim 3 further characterized in that the multiplied by the square-wave signal by means of a differential low-pass filter (15) is filtered.
5. The method of claim 4 further characterized in that the means of low-pass filter (15) filtered, multiplied by the square wave signal
Difference is filtered by a high-pass filter (16).
6. The method of claim 4 or 5, further characterized in that the filtered, multiplied by a square-wave signal difference is amplified.
7. Measuring system for performing a
Method according to one of claims 1 to 6, with a measuring sensor (3), a signal source (5) for energy supply of the measuring sensor (3), a calculation unit (22) having a reference signal input (6), a measurement signal input (7) and a signal output (8) has, wherein the calculation unit (22) comprises an amplifier (17) and is designed such that it from the reference signal input (6) and at the measuring signal input in operation adjacent (7) signals determines an amplified difference, characterized by a reference multiplexer (23) which is upstream of the reference signal input (6), and a measuring multiplexer (24) which is connected upstream of the measurement signal input (7), wherein from the reference multiplexer (23) a reference signal (r V f) or an attenuated reference signal (aV ref ) and (measuring from the multiplexer 24) a reference signal (V ref) or a measurement signal (V m8S3) can be output.
8. A measuring system according to claim 7, characterized in that the reference multiplexer (23), a signal attenuator (25) is connected upstream.
9. The measuring system according to claim 8, characterized in that a microcontroller (26) is provided by means of which the reference multiplexer (23), the measuring multiplexer (24), the calculation unit (22) and / or the signal source (5) can be controlled.
10. Measuring system according to one of claims 7 to
9, characterized in that the calculation unit (22) comprises a multiplier (10), which is designed such that it in operation, the difference from the reference signal input (6) applied signal and applied to the measurement signal input (7) signal with a square wave signal whose frequency is the frequency of the reference signal input terminal (6) or on the measuring signal output (7) corresponds incoming signal multiplied.
11. A measurement system according to claim 10, characterized in that the multiplier (10)
Low-pass filter (15) is connected downstream.
12. The measuring system according to claim 11, characterized in that the low-pass filter (15), an amplifier (17) or a high-pass filter (16) and the high-pass filter (16) downstream amplifier (17) are connected downstream.
13. Measuring system according to one of claims 7 to 12, characterized in that a reference sensor (2) is provided which can be supplied from the signal source with energy.
PCT/CH2007/000534 2006-11-02 2007-10-29 Method and measuring system for measuring a physical quantity WO2008052377A2 (en)

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CH17402006A CH698811B1 (en) 2006-11-02 2006-11-02 The method and measurement system for detecting and processing a physical quantity.
CH1740/06 2006-11-02

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WO2008052377A3 WO2008052377A3 (en) 2008-08-21

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Cited By (2)

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CN103884372A (en) * 2012-12-20 2014-06-25 克洛纳测量技术有限公司 Measuring assembly for the determination of a measurement value and method for generating an output signal
CN104614002A (en) * 2015-01-04 2015-05-13 中国科学院光电技术研究所 Subdivided signal error compensation method of photoelectric encoder of tracking control platform

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US4364028A (en) * 1978-06-30 1982-12-14 Tokyo Shibaura Denki Kabushiki Kaisha Integrating analog to digital converter having offset error compensation
US4873655A (en) * 1987-08-21 1989-10-10 Board Of Regents, The University Of Texas System Sensor conditioning method and apparatus
JPH0972757A (en) * 1995-09-01 1997-03-18 Murata Mfg Co Ltd Microcapacitance detection circuit
EP1037017A1 (en) * 1999-03-15 2000-09-20 Atsutoshi Goto Inductive position detector

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Publication number Priority date Publication date Assignee Title
US4364028A (en) * 1978-06-30 1982-12-14 Tokyo Shibaura Denki Kabushiki Kaisha Integrating analog to digital converter having offset error compensation
GB2072349A (en) * 1980-03-18 1981-09-30 Gaeltec Ltd Conditioning pressure transducer outputs
US4873655A (en) * 1987-08-21 1989-10-10 Board Of Regents, The University Of Texas System Sensor conditioning method and apparatus
JPH0972757A (en) * 1995-09-01 1997-03-18 Murata Mfg Co Ltd Microcapacitance detection circuit
EP1037017A1 (en) * 1999-03-15 2000-09-20 Atsutoshi Goto Inductive position detector

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103884372A (en) * 2012-12-20 2014-06-25 克洛纳测量技术有限公司 Measuring assembly for the determination of a measurement value and method for generating an output signal
CN104614002A (en) * 2015-01-04 2015-05-13 中国科学院光电技术研究所 Subdivided signal error compensation method of photoelectric encoder of tracking control platform

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CH698811B1 (en) 2009-10-30

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