DE102021109101A1 - Method and sensor for measuring a variable over time - Google Patents

Abstract

The present invention relates firstly to a method for providing a signal (01) to be transmitted to represent a measured value of a time-varying measured variable occurring at a measuring location, measured using a measuring method. The measured value measured with the measuring method is dependent on a gradient of a temperature (02) that occurs at the measuring location and changes over time. In one step of the method, the measuring method is used in order to continuously determine the measured value of the variable variable over time, with the gradient of the temperature (02) occurring at the measuring location being continuously determined at the same time. A measured value signal is formed, the amplitude of which depends on the measured value. In addition, a temperature gradient signal is formed, which represents at least one piece of information about the gradient of the occurring temperature (02) that varies over time. The temperature gradient signal is modulated onto the measured value signal in order to obtain the signal (01) to be transmitted. Furthermore, the invention relates to a sensor for measuring a measurement variable occurring at a measurement location that changes over time.

Description

The present invention first relates to a method for providing a signal to be transmitted to represent a measured value of a time-varying measured variable occurring at a measuring location, measured using a measuring method. The measured value measured with the measuring method depends on a gradient of a temperature occurring at the measuring location. Furthermore, the invention relates to a sensor for measuring a measurement variable occurring at a measurement location that changes over time.

the DE 101 45 669 A1 shows a distance sensor with a sensor element arranged in a housing, which can be influenced by an object that can be brought up to the housing from the outside. The distance sensor includes a signal circuit for generating an analog output signal as a function of a measurement distance between the object and the sensor element, and an output connection at which the measurement distance output signal can be tapped. A temperature sensor is arranged inside the housing. An output connection is provided, at which a temperature output signal can be tapped, which depends on the temperature determined with the temperature sensor.

From the DE 10 2006 024 920 A1 an inductive proximity switch with a sensor coil, with an oscillator, with a calibration unit and with an evaluation unit is known. The oscillator applies a high-frequency alternating current to the sensor coil. The balancing unit enables the switching distance to be adjusted and has two balancing resistors. The evaluation unit supplies a detection signal when the distance between an influencing element and the sensor coil has changed significantly. The adjustment unit also has a moisture compensation element.

the DE 100 06 691 A1 shows a method for temperature compensation of an LC oscillator having a processing head for capacitive measurement of a distance between the processing head and a workpiece. An output signal of the LC oscillator is transmitted to an evaluation device arranged separately from the processing head. With the help of a temperature sensor, the temperature of the LC oscillator is measured and sent to the evaluation device. Temperature compensation of the output signal of the LC oscillator takes place in the evaluation device based on the measured temperature and a temperature coefficient assigned to the processing head, which can also be transmitted from the processing head to the evaluation device.

From the DE 38 30 457 A1 a temperature sensor with a temperature transducer circuit is known, which supplies a voltage signal proportional to the absolute temperature. The voltage signal is processed by a storage circuit with a storage capacitor and by a control circuit. These circuits are designed in such a way that, on the one hand, the charging time of the storage capacitor is proportional to the value of the temperature-proportional voltage signal and, on the other hand, the discharging time is temperature-independent. Depending on the charging state of the storage capacitor, the control circuit generates a square-wave output signal whose period is proportional to the absolute temperature.

the WO 2019/063048 A1 teaches a contactless displacement sensor with a sensor element that is suitable for high temperatures and with electronics that are electrically coupled to the sensor element and have control and/or evaluation electronics. The electronics are designed for a temperature range above 125°C and are directly connected to the sensor element or integrated into the sensor element.

The use of measuring methods that lead to a measured value that is dependent on a gradient of a temperature that changes over time or that require a thermally steady state is complex, since the gradient of the temperature has to be determined and information about the gradient has to be transmitted to an evaluation location . This requires an additional channel for information transmission in the form of an additional electrical line, such as in particular an additional wire in a cable. This degrades the properties of the measuring system, since, for example, the minimum bending radii of the cable are increased and additional components are required, which can also fail.

Based on the prior art, the object of the present invention is to reduce the effort for the application of measuring methods which lead to a measured value dependent on a gradient of a temperature that changes over time or which require a thermally steady state.

Said object is achieved by a method according to appended claim 1 and by a sensor according to appended independent claim 10.

The method according to the invention serves to provide a signal to be transmitted. The signal to be transmitted represents a measured value of a measured variable that changes over time. Therewith the measured value is also variable over time. The measurand occurs at a measurement location. The measurement location forms the starting point for the transmission of the signal to be transmitted. The measured value is measured using a measuring method. The measurement method is thus applied at the measurement location. The signal to be transmitted quantitatively represents the measured value of the measured variable that changes over time. The signal to be transmitted can represent the measured value of the variable variable over time in unprocessed form or in already corrected form. The signal to be transmitted is preferably an analog signal.

The measured value measured with the measuring method is dependent on a gradient of a temperature that occurs at the measuring location and changes over time. The measured value is preferably independent of the temperature when the gradient of the temperature occurring at the measuring point is equal to zero, i. H. if there is a thermally steady state at the measurement location. The measured value then preferably has no error dependent on the temperature change. The gradient describes the change in temperature over time. The gradient describes in particular the increase or decrease in the course of the change in temperature over time. The gradient is a measure of this increase or decrease.

In one step of the method, the measuring method is used in order to continuously determine the measured value of the time-varying measured variable occurring at the measuring location. At the same time, the gradient of the time-varying temperature occurring at the measurement location is continuously determined. For this purpose, this temperature is preferably continuously measured.

In a further step, a measured value signal is formed, the amplitude of which depends on the measured value that changes over time. The measured value signal is therefore also variable over time. The measured value signal quantitatively represents the measured value that changes over time. The amplitude of the measured value signal is preferably proportional to the measured value that changes over time. However, the amplitude of the measured value signal can also be dependent on the measured measured value, which varies over time, according to a non-linear function.

In a further step, a temperature gradient signal is formed, which represents at least information about the gradient of the time-varying temperature occurring at the measurement location. The temperature gradient signal preferably represents at least information about the presence of the gradient of the time-varying temperature occurring at the measurement location, i. H. whether the gradient is noticeably different from zero. The temperature gradient signal thus represents the gradient of the time-varying temperature occurring at the measurement location, at least qualitatively. Correspondingly, the temperature gradient signal can at least be used to conclude whether the gradient of the time-varying temperature occurring at the measurement location exists, i. H. is non-zero; or conversely, whether a thermally steady state is given. In this respect, the temperature gradient signal represents at least information about whether or not a thermally steady state is present at the measurement location. The temperature gradient signal represents the gradient of the time-varying temperature occurring at the measurement location, preferably also quantitatively. It is thus possible to use the temperature gradient signal to draw conclusions about the size of the gradient of the temperature that occurs at the measurement location, which changes over time, in order in particular to be able to correct the measured value signal.

In a further step, the temperature gradient signal is modulated onto the measured value signal in order to obtain the signal to be transmitted. Thus, the resulting signal to be transmitted is a single signal, which represents the measured, time-varying measured value and the information about the gradient of the time-varying temperature occurring at the measurement location. From this single signal, the time-varying measured value and the information about the gradient of the time-varying temperature occurring at the measurement location can be unequivocally inferred.

A particular advantage of the method described is that only a single signal has to be transmitted from the measurement location in order to take into account the gradient of the temperature that occurs at the measurement location, which varies over time, for an evaluation remote from the measurement location, in order to determine the validity of the measured value signal or to to correct the measurement signal. There is no need to transmit the temperature gradient signal via an additional channel.

In preferred embodiments of the method, the gradient of the time-varying temperature occurring at the measurement location is determined at intervals. The temperature occurring at the measurement location is measured over one of several time intervals and the gradient of the change in temperature over time during this time interval is determined for this time interval. Thus, the temporal resolution is determined by the length of the time intervals. The time intervals are preferably of equal length. In these embodiments, the gradient at the measurement location occurring temperature is determined continuously over the multiple time intervals. The temperature occurring at the measurement location is preferably measured in quantized form; for example in steps of 1°C.

The modulation of the temperature gradient signal onto the measured value signal represents a superposition of these two signals. It can also be interpreted in such a way that the measured value signal is modulated onto the temperature gradient signal. The modulation is preferably formed by an amplitude modulation.

In preferred embodiments of the method, the measured value signal is in a first frequency range, while the temperature gradient signal is in a second frequency range. The second frequency range is spectrally spaced apart from the first frequency range above the first frequency range. Thus, the temperature gradient signal basically includes frequencies that are greater than frequencies of the measured value signal. The measured value signal and the temperature gradient signal thus differ spectrally, as a result of which they can be clearly identified, which can be used to separate these two signals after the transmission. In these embodiments, the temperature gradient signal forms an AC voltage component or a harmonic component of the signal to be transmitted.

In preferred embodiments of the method, a frequency of the temperature gradient signal represents the gradient of the time-varying temperature occurring at the measurement location quantitatively, which means that the magnitude of the gradient of the time-varying temperature occurring at the measurement location can be inferred with little effort. The frequency of the temperature gradient signal preferably increases with the gradient of the time-varying temperature occurring at the measurement location. The frequency of the temperature gradient signal is preferably proportional to the gradient of the time-varying temperature occurring at the measurement location. Alternatively, for example, an amplitude or a phase of the temperature gradient signal could also quantitatively represent the gradient of the time-varying temperature occurring at the measurement location.

In preferred embodiments of the method, the temperature gradient signal is periodic, so that it can be identified with little effort.

The periodic temperature gradient signal preferably has the form of a sine signal or a sawtooth signal. In principle, the periodic temperature gradient signal can also have other signal forms.

The periodic temperature gradient signal has an equivalent value, which is preferably equal to zero, so that it does not falsify the measured value signal. The equivalent is the arithmetic mean of the amplitude of the temperature gradient signal. In the preferred embodiment described above, in which the frequency of the temperature gradient signal is proportional to the gradient of the time-varying temperature occurring at the measurement location, the frequency becomes zero when the gradient of the time-varying temperature occurring at the measurement location is equal to zero, so that at an equivalent value from zero, the amplitude of the temperature gradient signal also becomes zero. The thermally steady state can thus be recognized by the fact that the temperature gradient signal has become zero.

In preferred embodiments of the method, the temperature gradient signal has an amplitude which is at most one-fifth as large as a mean amplitude of the measured value signal, so that the temperature gradient signal can be modulated onto the measured value signal with little effort. The amplitude of the temperature gradient signal is more preferably at most one tenth as large as a mean amplitude of the measured value signal.

In preferred embodiments of the method, the measured variable is a distance, a path, a speed, an acceleration, an angle of rotation, an angular velocity, an angular acceleration, a force, a torque, a pressure, a electrical voltage or formed by an electrical current. The measured variable is particularly preferably formed by a distance. This is preferably a distance in a machine, in particular in a machine tool or in an automobile.

In preferred embodiments, the measuring method is formed by an eddy current measuring method, by an inductive measuring method, by a capacitive measuring method, by a magnetic measuring method or by an optical measuring method. The measuring method is particularly preferably formed by an eddy current measuring method.

Preferred embodiments of the method are also designed to transmit the signal to be transmitted to an evaluation location. At the evaluation site, evaluation electronics are preferably arranged, which separates the transmitted signal into the measured value signal and the temperature gradient signal in order to use the temperature gradient signal to calculate the thermal to recognize the steady state or to correct the time-varying measured value based on the continuously determined gradient of the occurring temperature. The signal to be transmitted is transmitted as a single signal from the measuring location to the evaluation location in order to make the time-varying measured value and the information about the continuously determined gradient of the occurring temperature available at the evaluation location. If the temperature gradient signal represents the gradient of the occurring temperature only qualitatively, it is at least recognizable at the evaluation location whether the thermally steady state is present at the measurement location, so that it can be decided at the evaluation location whether the measured value signal is valid. If the temperature gradient signal quantitatively represents the gradient of the occurring temperature that varies over time, the measured value that varies over time can be corrected at the evaluation site on the basis of the gradient of the occurring temperature that is determined continuously. If the method is used in a machine tool, for example, the measurement location is preferably arranged on a tool of the machine tool, while the evaluation location is in a central electronic controller of the machine tool.

The signal to be transmitted is preferably transmitted as a single electrical signal via an electrical line. The signal to be transmitted is therefore single-channel. However, the signal to be transmitted can, for example, also be transmitted wirelessly as a single-channel radio signal.

The sensor according to the invention is used to measure a measurement variable occurring at a measurement location that changes over time. The sensor is based on a measuring method for measuring the variable variable over time. The sensor is designed to measure a measured value of the measured variable. The measured value depends on a gradient of a temperature occurring at the measurement location. The sensor is configured to provide a signal to be transmitted according to the method described above. The sensor is preferably configured to provide a signal to be transmitted according to one of the preferred embodiments of the method described above. The sensor also preferably has features that are specified in connection with the method described above.

A particular advantage of the sensor is that it does not have to have an additional output channel for the temperature gradient signal, so that it can be made compact and inexpensive.

The sensor is preferably a distance sensor. The sensor is preferably based on an eddy current measurement.

In addition to a sensor element for measuring the measured variable, the sensor preferably also includes a temperature sensor element for measuring the temperature occurring at the measurement location.

Further details, advantages and developments of the invention result from the following description of a preferred embodiment of the invention, with reference to the drawing

The only figure shows a diagram of a signal 01 to be transmitted, which, according to a preferred embodiment of a method according to the invention, is based on a measured value of a measurement variable occurring at a measurement location that changes over time (not shown) and on an example of a time profile 02 of a measurement occurring at the measurement location temperature is provided. A profile of an amplitude A over a time t is shown in each case. The amplitude A of the signal 01 to be transmitted primarily represents the measured value of the measured variable, which is preferably a distance which is measured using an eddy current sensor (not shown). A temperature gradient signal formed by an AC voltage signal is then modulated, which quantitatively represents a temperature gradient which was determined based on the time course 02 of the temperature occurring at the measurement location. In this embodiment, this temperature gradient signal is sawtooth-shaped. The higher the gradient of the time curve 02 of the temperature occurring at the measurement location, the higher the frequency of the temperature gradient signal. In a first time segment 03, there is a medium-sized gradient of the time profile 02 of the temperature occurring at the measurement location, so that the temperature gradient signal has a medium-sized frequency. In a second time section 04 there is a large gradient of the time profile 02 of the temperature occurring at the measurement location, so that the temperature gradient signal has a high frequency. In a third time section 06, the gradient of the time profile 02 of the temperature occurring at the measurement location is equal to zero, so that the temperature gradient signal has a frequency of zero, which means that the amplitude of the temperature gradient signal also disappears, so that the signal 01 to be transmitted only consists of the measured value signal representing the measured value. In a fourth time section 07, there is a small gradient of the time profile 02 of the temperature occurring at the measurement location, so that the temperature gradient signal has a low frequency.

Reference List

01

signal to be transmitted

02

Time course of a temperature occurring at a measurement location

03

first period of time

04

second time period

05

-

06

third time period

07

fourth period

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 10145669 A1 [0002]
• DE 102006024920 A1 [0003]
• DE 10006691 A1 [0004]
• DE 3830457 A1 [0005]
• WO 2019063048 A1 [0006]

Claims (10)

Method for providing a signal (01) to be transmitted to represent a measured value measured using a measuring method of a variable over time occurring at a measuring location, the measured value measured using the measuring method being dependent on a gradient of a temperature (02) changing over time occurring at the measuring location, and wherein the method comprises the steps of: - Application of the measuring method in order to continuously determine the measured value of the time-varying measured variable occurring at the measuring location, the gradient of the temperature (02) occurring at the measuring location being continuously determined at the same time; - Forming a measured value signal, the amplitude of which is dependent on the measured value that changes over time; - Forming a temperature gradient signal, which represents at least one piece of information about the gradient of the time-varying temperature (02) that occurs; and - Modulating the temperature gradient signal onto the measured value signal in order to obtain the signal to be transmitted (01). procedure after claim 1 , characterized in that the measured value signal is in a first frequency range and that the temperature gradient signal is in a second frequency range, wherein the second frequency range is spectrally spaced from the first frequency range above the first frequency range. procedure after claim 1 or 2 , characterized in that the temperature gradient signal represents the gradient of the time-varying temperature (02) occurring quantitatively. procedure after claim 3 , characterized in that a frequency of the temperature gradient signal represents the gradient of the occurring temperature (02) quantitatively. Procedure according to one of Claims 1 until 4 , characterized in that the temperature gradient signal is periodic and has the form of a sine wave or a sawtooth signal. procedure after claim 5 , characterized in that the periodic temperature gradient signal has an equivalent value which is equal to zero. Procedure according to one of Claims 1 until 6 , characterized in that the measured variable by a distance, by a path, by a speed, by an acceleration, by an angle of rotation, by an angular velocity, by an angular acceleration, by a force, by a torque, by a pressure, by an electric Voltage or is formed by an electric current. Procedure according to one of Claims 1 until 7 , characterized in that the measuring method is formed by an eddy current measuring method, by an inductive measuring method, by a capacitive measuring method, by a magnetic measuring method or by an optical measuring method. Procedure according to one of Claims 1 until 8th , characterized in that it is also designed to transmit the signal (01) to be transmitted to an evaluation location, for which purpose the signal (01) to be transmitted is transmitted as a single signal (01) from the measurement location to the evaluation location in order to measure the temporally variable at the evaluation location To provide the measured value and the information about the continuously determined gradient of the occurring temperature (02). Sensor for measuring a measurement variable occurring at a measurement location that changes over time, the sensor being based on a measurement method and being designed to measure a measured value which is dependent on a gradient of a temperature (02) occurring at the measurement location, and the sensor providing a transmitted signal (01) according to a method according to one of Claims 1 until 9 is configured.

Images