EP3556019A1 - Linearization circuit and method for linearizing a measurement signal - Google Patents
Linearization circuit and method for linearizing a measurement signalInfo
- Publication number
- EP3556019A1 EP3556019A1 EP17832737.5A EP17832737A EP3556019A1 EP 3556019 A1 EP3556019 A1 EP 3556019A1 EP 17832737 A EP17832737 A EP 17832737A EP 3556019 A1 EP3556019 A1 EP 3556019A1
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- European Patent Office
- Prior art keywords
- signal
- input
- charging
- comparator
- output
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000005259 measurement Methods 0.000 title claims abstract description 67
- 238000000034 method Methods 0.000 title claims abstract description 13
- 239000003990 capacitor Substances 0.000 claims abstract description 66
- 238000007599 discharging Methods 0.000 claims abstract description 36
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Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
- H03M1/50—Analogue/digital converters with intermediate conversion to time interval
- H03M1/58—Non-linear conversion
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
- G01K7/14—Arrangements for modifying the output characteristic, e.g. linearising
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/005—Circuits for altering the indicating characteristic, e.g. making it non-linear
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
- H03M1/50—Analogue/digital converters with intermediate conversion to time interval
- H03M1/504—Analogue/digital converters with intermediate conversion to time interval using pulse width modulation
Definitions
- the present invention relates to a linearization circuit for linearizing a measurement signal, wherein the linearization circuit has an input for inputting the measurement signal and an output for outputting a linearized output signal.
- the invention further relates to a corresponding method.
- a physical quantity such as a distance, a position, a temperature, a wavelength, an illumination intensity, a (magnetic or electric) field strength or a force must often be measured and converted into an electrical signal.
- This electrical signal - the measuring signal - can then be further processed with an electrical circuit. It is usually important that there is a linear relationship between the physical quantity and the measurement signal. This means that the measurement signal also changes linearly with a linear change of the physical quantity. Such a linear relationship considerably facilitates the use of the measurement signal.
- the sensors or sensor arrangements used for such measurements do not have linear characteristics, i. the measurement signal is in a nonlinear relationship to the physical quantity. In this case, the measurement signal must be linearized. In most cases, a considerable effort in hardware and / or software is required.
- look-up tables which require a corresponding storage space and must be completely recalculated for small changes in the raw signal.
- the present invention is therefore based on the object, a linearization circuit and a method of the type mentioned in such a way and further, that a linearized output signal or a signal for a linearized signal signal can be generated with the least possible effort and at the lowest possible cost ,
- the linearization circuit in question is characterized by: a reference component having a nonlinear dependence on current or voltage, the voltage applied across the reference component or a voltage derived from a current flowing through the reference component, a reference signal (U c ) or an alternating component of a reference signal (U c ) forms,
- a charging and discharging controller configured to control alternate charging and discharging of the reference member, wherein the controlling of charging and discharging is performed such that the reference signal (U c ) has a substantially periodic course
- a comparator circuit having a first input, a second input and an output, wherein the reference signal (U c ) is applied to the first input and the measurement signal (Ud) to the second input and wherein the comparator circuit is configured based on a reference time during a charge-discharge cycle and a result of a comparison of the reference signal (U c ) with the measurement signal (Ud) at its output to generate and output a square wave signal (U a ), so that the square wave signal represents a linearized output signal.
- nonlinear characteristics of sensors or sensor arrangements are very often curves which have a decreasing absolute slope.
- the slope of the characteristic curves of many non-linear sensors or sensor arrangements are greater in the lower part of the measuring range and thus offers a higher sensitivity than in the upper range.
- the characteristic curve increasingly flattens out.
- electronic devices with nonlinear dependence on voltage or current have a very similar behavior.
- Such components are, for example, a capacitor (capacitor) or an inductance (coil).
- a non-linear dependence of voltage or current means that the voltage across the device or the current through the device does not vary linearly with constant excitation.
- the example of a capacitor and a coil this is clarified more precisely.
- the voltage U c across the capacitance runs when applying a DC voltage Ub - the constant excitation - according to the equation:
- ⁇ is a time constant with which the voltage U c increases exponentially and which depends on the size of the capacitance and the resistance over which the capacitance is charged.
- RL is the ohmic resistance of the coil and ⁇ is a time constant with which the current through the coil increases exponentially.
- the current can be used to form a reference signal, for example, by converting the current flow into a corresponding voltage drop.
- a resistor can be used, which is flowed through by this current.
- the derived voltage may form the reference signal itself or the alternating component of the reference signal.
- This reference signal is compared with the measurement signal. So that the comparison can not be carried out once only, a loading and unloading process is carried out periodically. Under charging or discharging is understood in each case the feeding or removal of energy. In the case of a capacitor, this means that an electric field is built up in the capacitor (charging) or the electric field is reduced (discharging). With a coil, a magnetic field would build up (charge) or degrade (discharge).
- a linearization circuit which utilizes this effect, has a reference component, a charge and discharge control and a comparator circuit.
- the charging and discharging control is designed to control an alternating charging and discharging of the reference component. In doing so, the Controlled loading and unloading controlled so that the reference signal takes a substantially periodic course. In practice, this is achieved by starting a new charging process after a fixed period length T.
- the voltage across the reference component or a voltage derived from a current flowing through the reference component is used as a reference signal or forms an alternating component of a reference signal. In the latter case, the voltage across the reference component or the voltage derived from the flowing current would be offset by an offset.
- the comparator circuit has a first input, a second input and an output.
- the reference signal is switched to the first input and the measurement signal to the second input.
- the comparator circuit compares the reference signal with the measurement signal and generates based on the result of the comparison at its output a square wave signal.
- a reference time is used during a charge-discharge cycle. This results in a variable period, which is dependent on the reference time and the time of changing a comparison result and represents a linearized output signal. Namely, the larger the measurement signal, the later in a loading branch of a charge-discharge cycle, the comparison result between the measurement signal and the reference signal changes. As a result, the effect of the flattening characteristics of the sensor or of the sensor arrangement is compensated by the charging behavior of the reference component.
- the square-wave signal is thus a pulse-width-modulated output signal which represents a linearization of the measurement signal.
- a DC voltage which depends on the measured physical quantity is regarded as the measurement signal.
- Such a DC voltage is often directly present in non-linear sensors or sensor arrangements or can be generated in a simple manner. If, for example, the sensor or the sensor arrangement comprises an eddy-current sensor whose frequency depends on the distance of a measuring object, then this frequency can easily be converted into a corresponding DC voltage.
- the rectangular signal is considered to be an alternating signal which changes between a first level and a second level. In this case, the change between a first level and a second level in comparison to the period length T of the rectangular signal is significantly smaller. Usually the level changes are completed in less than 1% of the period length.
- a first level is a high level and a second level is a low level.
- the ratio between a charging phase and a subsequent discharging phase of the capacitor can assume relatively arbitrary values, as long as the charging phase lasts sufficiently long and thus provides a sufficiently good resolution of the linearization and as long as the reference component is completely discharged at the beginning of a new charging phase. If the reference component is formed by a capacitor, the capacitor would have to be completely discharged at the beginning of a new charging phase. In the case of a coil as an implementation of the reference component, the coil would have to have completely escaped at the beginning of a new charging phase.
- the ratio can be suitably selected depending on the measurement signal, which depends on characteristic features of the respective sensor.
- the reference component is charged for at least 40% of the period length of a charge-discharge cycle.
- the discharge phase preferably takes a maximum of 50% of the period length of a charge-discharge cycle, wherein the unloading of the reference component is preferably completed faster than the discharge phase continues. Most preferably, the loading phase and the discharge phase is the same length.
- the reference component is formed by a capacitor / capacitor. Since the voltage drop during the energization or de-energization of a coil has an analogous non-linear behavior, a person skilled in the art will be able to transfer the embodiments from a capacitor to immediately detect a coil or other reference device with a nonlinear dependence on current or voltage.
- the comparator circuit can in principle be designed in a variety of ways. It is essential that a rectangular signal can be generated, the level change of which depends on a reference time during a charge-discharge cycle and a result of a comparison between the reference signal and the measurement signal. Such circuits are known in practice. As an example, divider stages are mentioned here, which receive the clock from stable quartz-based oscillators.
- this comprises a comparator and a flip-flop.
- the comparator in turn has a first and a second input, which are each connected to the corresponding input of the comparator circuit. Accordingly, the reference signal would be input to the first input of the comparator and the measurement signal to the second input of the comparator.
- the comparator itself compares the two signals input to the first and second inputs of the comparator circuit, i. the reference signal and the measurement signal to each other and outputs the result of the comparison to the flip-flop.
- the flip-flop generates the square-wave signal using this comparison result and outputs it via the output of the comparator circuit.
- the comparator is designed as an operational amplifier, which is connected as a Schmitt trigger. Thereby, the comparator outputs either a first level or a second level. According to a preferred implementation, the comparator outputs a low level when the reference signal is smaller than the measurement signal while the comparator outputs a high level when the reference signal is greater than the measurement signal.
- a D flip-flop has a data input (D), a clock input (CLK) and a reset input (R), wherein the setting of the output (Q) by a constant high level at the data input and an edge change of Low to high level is triggered at the clock input.
- An activation event on the reset input causes the flip-flop to be reset.
- Such an activation event is in practice usually the exceeding of a predefined level - activation level - or a rising edge of the applied signal.
- the flip-flop is set edge-controlled. Resetting the flip-flop, however, is level-controlled as soon as the activation level at the reset input is exceeded.
- the clock input is connected to the charge and discharge controller.
- the flip-flop would be tuned to the charge and discharge control, that at the beginning of a charging of the capacitor, the flip-flop is set, because the data input is permanently a high level. In this way, substantially simultaneously with the charging of the capacitor via the clock input, the flip-flop would be set, so that in a very simple manner, a reference time is formed during a charge-discharge cycle, namely the beginning of a charging of the capacitor.
- the output of the comparator is preferably connected to the reset input of the D flip-flop.
- the comparator can generate a signal that is suitable as an activation event for resetting the flip-flop. That when the comparison result is changed, the comparator outputs either a level change corresponding to the flip-flop or an appropriate level to the reset input of the flip-flop.
- Such a connection of a D flip-flop produces a rectangular signal at the output of the flip-flop, which depends on a reference time and on a result of a comparison between the measuring signal and the reference signal.
- the comparison result of the comparator can also be entered in the set input.
- other types of flip-flops such as RS flip-flops can be used.
- the circuitry of the flip-flop is quite analogous to adapt so that the desired result is present at the output.
- a simple AND gate could also be used. At the first input of the AND gate, a clock signal is applied, at the second input the comparison result from the output of the comparator. In this embodiment, it is favorable if the comparator outputs a high level, if the reference signal is smaller than the measuring signal.
- the output of the AND gate is at high level.
- the comparator switches to low level at the output. This means that a low level is present at the second input of the AND gate, as a result of which the gate at the output likewise switches to low level.
- the output of the AND gate remains low even when the clock signal goes low. The duration of the concern of the high level at the output of the gate is thus dependent on a reference time and on a result of a comparison between the measurement signal and the reference signal.
- the linearization circuit additionally comprises a first resistor and a second resistor, the first resistor being used for charging the capacitor and the second resistor for discharging the capacitor.
- the first resistor is preferably formed by a temperature-stable resistor.
- the second resistor could also be made temperature-stable. However, this is not necessarily necessary, since usually carried out only during the charging phase, a comparison of the reference signal with the measurement signal and thus the discharge branch not used. Regardless of whether the second resistor is thermally stable or not, it should be ensured that the discharging process of the capacitor is sufficiently fast.
- the second resistor in comparison to the first resistor is preferably dimensioned such that the discharging of the capacitor is faster than the charging of the capacitor.
- the first and the second resistor are preferably dimensioned such that the time for charging the capacitor is at least twice as long as the time for discharging the capacitor, ie the discharge of the capacitor is twice as fast as charging the capacitor.
- the first resistor can be designed to be adaptable in a further development. This can be achieved by adjustability of the resistor itself or by parallel or series connection of an adjustable resistor to the first resistor. Such adaptability can be achieved, for example, by a digital-to-analog converter or by digital potentiometer which is connected in parallel or in series with the first resistor.
- Another way to adjust the linearization circuit is to change the capacitance of the capacitor.
- This can be achieved by means of an adjustable capacitor, in which case it does not matter in principle whether it can be adjusted mechanically (eg trim capacitor), is electrically adjustable (eg capacitance diode) or can be digitally adjusted (eg by integrated circuits with appropriate interface or by adding or removing capacitors).
- this coil could be adjusted by an adjustable core.
- the linearization circuit can be made adaptable by adapting the reference component. This can influence the charging and discharging behavior.
- potentiometers, power supplies, digital-to-analog converters, digital pots, reference voltage sources, etc. are listed here.
- the linearization circuit may have a switching device with at least one control input, a first input, a second input and an output.
- the switching device is preferably designed such that it switches either the first input or the second input to the output in response to a control signal at the at least one control input.
- the at least one control input is connected to the charge and discharge control, so that the switching device can be controlled based on control signals from the charge and discharge control.
- One terminal of the first resistor is connected to the first input of the switching device, while a terminal of the second resistor is connected to the second input of the switching device.
- the second terminal of the first resistor may be connected to a voltage source and the second terminal of the second resistor to ground potential.
- the output of the switching device would be connected to one terminal of the capacitor.
- the capacitor could either be connected (and therefore charged) via the first resistor to a voltage source or could be pulled (and thus discharged) via the second resistor to ground potential. In this way, based on control signals from the charging and discharging capacitor can be charged or discharged.
- the capacitor could also be made temperature-stable.
- the capacitor could have a temperature coefficient ⁇ whose magnitude is less than 10 -3 / K, preferably less than 1 CH / Kelvin In a very particularly preferred development, the temperature coefficient ⁇ is 0.
- a corresponding capacitor with a temperature coefficient equal to 0 is, for example a Class 1 ceramic capacitor according to IEC / EN 60384-8 / 21, also known as NPO (negative-positive-zero) capacitor According to the EIA RS-198 codes, such a capacitor is referred to as C0G.
- the rectangular signal generated by the linearization circuit according to the invention is already representative of a linearized output signal.
- the square wave signal represents a pulse width modulated signal, i. the ratio between a high level and the period length of the square wave signal is representative of the linearized output signal.
- the linearization circuit in a preferred development can have a low-pass filter to which the square-wave signal is applied. The low pass would thereby generate from the square wave signal a DC voltage derived from the square wave signal. In a particularly simple embodiment of the low-pass filter, this can be formed by a simple RC element. To avoid influencing the output signal of temperature fluctuations, the low pass could be formed by temperature-stable elements.
- linearization circuit according to the invention or its further developments can do without the use of special modules.
- this does not limit the resolution of the linearization circuit by digitizing stages, such as analog-to-digital converters. Rather, the circuit can be implemented by a few discrete components and simple integrated circuits.
- the resolution of the circuit is largely determined only by the roughness See the individual components limited, but usually well below the quantization noise of conventional analog-to-digital converter. This helps to provide a low cost and reliable linearization circuit with high accuracy and resolution.
- parts of the linearization circuit may also be implemented in a microcontroller. This can be done particularly easily during charging and discharging control. In this way, the charging and discharging of the capacitor can be configured flexibly programmable.
- a microcontroller could also be used to control a customizable first resistor, if present, or a customizable resistor connected in parallel or in series with the first resistor. Corresponding components are known from practice.
- the microcontroller could also be used to evaluate the rectangular signal output by the comparator circuit. This could be realized, for example, by counting reference oscillations, such as the clock signal of the microcontroller. In this way, a simple and cost-effective digitization of the linearized output signal can be made possible in which any resolutions can be achieved by longer counting phases.
- the microcontroller can generate the voltages that may be needed to charge or discharge the reference component.
- PWM modules of the microcontroller could be used together with an external low-pass filter.
- FIG. 2 shows a diagram with the reference signal according to FIG. 1 together with a measuring signal Ud and a rectangular signal U a
- 2a is a diagram with the reference signal U c and the measurement signal Ud together with a clock signal CLK, a signal at a reset input of a D flip-flop and a signal at the output Q of the D flip-flop,
- FIG. 3 shows a diagram with a measuring signal used by way of example
- Fig. 4 is a diagram with the linearization error of the measurement signal after
- FIG. 5 shows a diagram with the linearized output signal of the linearization circuit according to the invention, wherein the output signal is rectified by a low-pass filter, and
- FIG. 7 shows an exemplary circuit for linearizing a measurement signal using a capacitor as a reference component
- FIG. 8 shows an exemplary circuit for the linearization of a measurement signal using a coil as a reference component.
- FIG. 1 shows a diagram with a time characteristic of a reference signal that can be generated and used by a linearization circuit according to the invention.
- a voltage U c is plotted against the time t.
- the reference signal is constructed by a sequence of charging and discharging phases of a capacitor of the linearization circuit.
- a temperature-stable capacitor preferably COG or NPO
- Charging takes place via a temperature-stable first resistor and follows a typical capacitor charging curve.
- Discharging takes place via a second resistor in such a way that discharging is faster than charging, so that the stable starting state is reached again very quickly.
- At the discharge resistor - second resistor - no special requirements for accuracy or temperature stability must be made.
- a charging phase 1 of the capacitor is followed in each case by a discharging phase 2 of the capacitor or vice versa.
- a discharging phase 2 of the capacitor is started, d. H.
- the charging and discharging of the capacitor is controlled so that a periodic reference signal with a period length T is formed. In the exemplary embodiment illustrated in FIG. 1, this is approximately 0.8 ms. It can be seen that the charge and discharge phase change approximately after half a period length. Not all of the discharge phase is required to discharge the capacitor. This ensures that the capacitor is actually discharged at the beginning of a new charging phase and thus at the start of a new charge-discharge cycle.
- the linearization circuit has a comparator circuit, which comprises a comparator and a D flip-flop in the exemplary embodiment illustrated here.
- the comparator compares the reference signal U c with the measurement signal Ud.
- the measurement signal Ud is the already converted DC voltage, which depends on a measured physical quantity.
- the flip-flop is set, whereby its output voltage U a goes to logic "1", ie assumes a high level If the reference signal U c is greater than the measuring signal Ud, the comparator switches over and sets the flip-flop back to logical "0", ie to a low level.
- FIG. 2 shows in addition to the reference signal U c of FIG. 1 is a time course of a measurement signal Ud and a square wave signal U a , which is generated by the linearization circuit.
- the measurement signal Ud increases according to the characteristic of the sensor that has generated this measurement signal.
- FIG. 2 a shows the time sequence of the reference signal U c and of the measuring signal U d and the associated level states on a D flip-flop. The clock signal controls - as described above - the emergence of the curve U c by a capacitor is charged when switching to high level and discharged when switching to low level again.
- the clock signal is applied to the CLK input of the D flip-flop. If the D input of the flip-flop is always at logic 1 (high level), output Q is set with the rising edge of the clock signal.
- the comparator constantly compares Ud with U c . If Ud is greater than U c ., The output of the comparator jumps from 0 to 1. This output signal is applied to the R input of the flip-flop and causes a reset of the flip-flop. The output Q thus goes to logic 0 (low level).
- the duration of the high level at the Q output of the D flip-flop is thus dependent on a reference time and on a result of a comparison between the measurement signal and the reference signal and thus represents the linearized measurement signal.
- the characteristic curve of the sensor is shown completely in FIG.
- the sensor is an eddy current measuring system which determines the distance of a measuring object from the measuring system. Accordingly, in FIG. 3, the measurement signal Ud is plotted against the measured distance d. It can be seen that with a small measuring distance, the sensitivity of the measuring system is high and therefore the characteristic increases rapidly. With increasing distance, the sensitivity becomes smaller, which manifests itself in a flatter characteristic curve. The result is an exponential curve for the measurement signal Ud as a function of the distance d. If the characteristic line is completely traversed during a measurement (ie the distance from the beginning of the measuring range to the end of the measuring range is constantly increased), the exponential rising curve Ud shown in FIG. 2 is obtained as a time-dependent curve.
- the measurement signal Ud is compared with an exponential AC voltage U c and generates a square wave voltage U a .
- U c an exponential AC voltage
- U a a square wave voltage
- the pulse width (logic "1" of the flip-flop) thus increases with increasing distance, so that the width of the pulses is a direct measure of the measured original size, which has been linearized in a particularly simple way by the linearization circuit applied to a low-pass, for example, a simple RC element, one obtains an output voltage which is linear relative to the original physical quantity, thus linearizing by reducing the voltage contributions to the characteristic in the high sensitivity range (lower pulse width) and in the low sensitivity range be amplified (higher pulse width).
- a pulse of the rectangular signal always begins with a charging phase.
- the square-wave signal U a jumps from a low level (approximately 0 V) to a high level (approximately 5 V) at the beginning of a charging phase (recognizable by the incipient rise of the reference signal Uc).
- the beginning of a charging phase forms a reference time during a charge-discharge cycle.
- the square wave signal remains at the high level until the reference signal U c is the same size as the measurement signal Ud.
- the square wave signal U a falls to the low level and remains there until a new charge-discharge cycle is started. It can also be clearly seen that the pulse width changes with increasing measurement signal.
- FIG. 4 shows the linearization error in percent, which results for the characteristic curve according to FIG. 3. It can be seen that the measurement signal Ud deviates significantly from a linear characteristic. The characteristic differs by more than ⁇ 10% from a linear characteristic.
- FIG. 5 shows a characteristic curve linearized by means of a linearization circuit according to the invention. Already from Fig. 5 it can be seen that the output voltage U a of the linearization circuit deviates little from a straight line.
- FIG. 6 clarifies this again in the form of the linearization error of the linearized output signal. It can be seen that the linearization error has significantly reduced. Most values are in a band of approximately ⁇ 0.5%.
- Fig. 7 shows a first embodiment of a linearization circuit according to the invention, this first embodiment uses a capacitor C as a reference component.
- the capacitor C has a very small temperature coefficient and is preferably an NPO capacitor.
- One terminal of the capacitor C is connected to the output of a switching device 3, while the second terminal is at ground potential.
- the switching device 3 has a first input 4, a second input 5 and a control input 6, the switching device depending on the signal at the control input 6, the first input 4 or the second input 5 connects to the output.
- a first voltage source U1 is connected via a first resistor R1.
- the first resistor R1 is designed as a temperature-stable resistor.
- the second input 5 is connected via a second resistor R2 to a second voltage source U2.
- the voltage of the first voltage source U1 is greater than the voltage of the second voltage source U2.
- the second voltage source U2 is not present and the second input of the switching device is connected via the resistor R2 to ground. This optional embodiment is indicated by a dashed line next to the second voltage source U2.
- the control input 6 of the switching device 3 is connected to a clock 7, so that the clock 7 serves as a charge and discharge control in the context of the invention.
- the output signal of the clock 7 is additionally input to the clock input CLK of a D flip-flop 8, which forms a comparator circuit 10 together with a comparator 9.
- the data input D of the flip-flop 8 is supplied with a high level.
- the reset input R is connected to the output of the comparator 9.
- a rectangular signal Ua is output, which represents a linearized measurement signal.
- a first input 1 1 of the comparator 9 is connected to the capacitor C and the output of the switching device. In a second input 12 of the comparator 9, the measurement signal Ud is entered.
- the output of the flip-flop 9 can with a low pass 13, which is shown in dashed lines in Fig. 7 as an optional supplement and is formed by a series circuit of a resistor and a capacitor. At the junction between resistor and capacitor is then a rectified linearized output signal Ua.dc.
- the clock 7 in conjunction with the switching device 3 ensures that the capacitor C is continuously charged and discharged. Due to the periodic design of the control signal, the voltage across the capacitor C also assumes a periodic course, which essentially corresponds to the course shown in FIG.
- the period length T is defined by the period length of the output signal of the clock 7.
- the voltage across the capacitor C forms the reference signal U c in this circuit.
- FIG. 8 shows a second exemplary embodiment of a linearization circuit according to the invention, this second exemplary embodiment using a coil L as the reference component.
- the comparator circuit 10, the clock 7 and the optional low-pass filter 13 are interconnected as in the first embodiment. Only the generation of the reference signal differs significantly.
- a switching device 14, which is designed as an opener or closer, is connected between a voltage source U1 and a first terminal of the coil L.
- a control input of the switching device 14 is connected to the output of the clock 7.
- a second resistor R2 is also connected, whose second terminal is connected to ground.
- a first resistor R1 is connected, whose second terminal is connected to a second voltage source or (optionally) to ground.
- the voltage at the second terminal 16 of the coil L is input to the second input 12 of the comparator 9.
- the control signal at the control input of the switching device 14 ensures that the coil L is periodically charged and discharged.
- the first terminal 15 of the coil L is connected to the voltage source U1 and thereby on raised a higher potential. This leads to a current flow through the coil L and the resistor R1, which is invited into the coil L energy.
- the coil L is discharged via resistor R2 and resistor R1. This creates a voltage drop across resistor R1, which is dependent on the current flow through the coil. This voltage drop is used to generate a reference signal. If a second voltage source U2 is present, the voltage drop across resistor R1 forms the alternating component of the reference signal. If a connection to ground (instead of the second voltage source U2) is optionally provided, the voltage drop across resistor R1 forms the reference signal. Otherwise, the circuit has the behavior described above.
- the circuit can be realized using a microcontroller.
- the microcontroller can control the clock generation, the switching of the capacitor between charging and discharging phase and optionally the flip-flop.
- a DA converter which may already be included in the microcontroller, an adjustment of the circuit to real sensors are performed by the resistance value of the temperature-stable first resistor is adjusted by the parallel-connected DA converter.
- a controlled by the microcontroller adjustment of real sensors is fast and easy to implement.
- the resolution of the linearization circuit does not depend on digital components such as an AD converter or DA converter of the microcontroller.
- digital components such as an AD converter or DA converter of the microcontroller.
- the signals U c and U d are identical, only analog components are used (comparator), so that the resolution is limited only by the noise of these components.
- a very simple, inexpensive microcontroller can be used for the circuit, since it only performs control tasks.
- the other components of the circuit are simple, passive components, so that thus a very inexpensive, very easy to set digitally circuit with high accuracy and resolution can be realized.
- only very few temperature-stable components are necessary, which further positively influences the costs.
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- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Theoretical Computer Science (AREA)
- Indication And Recording Devices For Special Purposes And Tariff Metering Devices (AREA)
- Manipulation Of Pulses (AREA)
Abstract
Description
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Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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DE102016225044.2A DE102016225044A1 (en) | 2016-12-14 | 2016-12-14 | Linearization circuit and method for linearizing a measurement signal |
PCT/DE2017/200130 WO2018108216A1 (en) | 2016-12-14 | 2017-12-07 | Linearization circuit and method for linearizing a measurement signal |
Publications (1)
Publication Number | Publication Date |
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EP3556019A1 true EP3556019A1 (en) | 2019-10-23 |
Family
ID=61017727
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EP17832737.5A Pending EP3556019A1 (en) | 2016-12-14 | 2017-12-07 | Linearization circuit and method for linearizing a measurement signal |
Country Status (6)
Country | Link |
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US (1) | US10700698B2 (en) |
EP (1) | EP3556019A1 (en) |
JP (1) | JP6979070B2 (en) |
CN (1) | CN110291720B (en) |
DE (1) | DE102016225044A1 (en) |
WO (1) | WO2018108216A1 (en) |
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CN113358015A (en) * | 2021-04-16 | 2021-09-07 | 上海兰宝传感科技股份有限公司 | Eddy current displacement sensor and method for expanding linear range thereof |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3277395A (en) * | 1963-11-18 | 1966-10-04 | Gen Electric | Pluse width modulator |
US3460068A (en) | 1965-06-10 | 1969-08-05 | Bell Telephone Labor Inc | Instantaneous compandor utilizing the sampled pulse response of a linear time-invariant network |
US3691473A (en) | 1968-08-19 | 1972-09-12 | Northeast Electronics Corp | Voltage ratio apparatus with logarithmic output |
EP0148296B1 (en) * | 1984-01-09 | 1988-06-22 | Leybold Aktiengesellschaft | Method and circuit for converting a measuring current into an impulse rate proportional to the measuring current |
JPH05218826A (en) * | 1992-02-04 | 1993-08-27 | Fujitsu Ltd | Semiconductor device |
US6339352B1 (en) * | 2001-03-19 | 2002-01-15 | York International Corporation | Anticipatory Schmitt trigger |
CN2677895Y (en) * | 2003-09-03 | 2005-02-09 | 上海复旦微电子股份有限公司 | Temp. measuring circuit |
DE102004023145A1 (en) * | 2004-05-07 | 2005-11-24 | Endress + Hauser Wetzer Gmbh + Co. Kg | Device for analog / digital conversion of a measuring voltage |
US7288946B2 (en) * | 2005-06-03 | 2007-10-30 | Synaptics Incorporated | Methods and systems for detecting a capacitance using sigma-delta measurement techniques |
US8570053B1 (en) * | 2007-07-03 | 2013-10-29 | Cypress Semiconductor Corporation | Capacitive field sensor with sigma-delta modulator |
US7982427B2 (en) * | 2008-05-09 | 2011-07-19 | Renault S.A.S. | Voltage measurement of high voltage batteries for hybrid and electric vehicles |
EP2128579B1 (en) * | 2008-05-28 | 2012-08-01 | Sensata Technologies, Inc. | Arrangement for linearizing a non-linear sensor |
US8979362B2 (en) * | 2012-02-15 | 2015-03-17 | Infineon Technologies Ag | Circuit and method for sensing a physical quantity, an oscillator circuit, a smartcard, and a temperature-sensing circuit |
-
2016
- 2016-12-14 DE DE102016225044.2A patent/DE102016225044A1/en active Pending
-
2017
- 2017-12-07 WO PCT/DE2017/200130 patent/WO2018108216A1/en unknown
- 2017-12-07 US US16/469,326 patent/US10700698B2/en active Active
- 2017-12-07 CN CN201780086289.5A patent/CN110291720B/en active Active
- 2017-12-07 EP EP17832737.5A patent/EP3556019A1/en active Pending
- 2017-12-07 JP JP2019531807A patent/JP6979070B2/en active Active
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US20200021306A1 (en) | 2020-01-16 |
JP6979070B2 (en) | 2021-12-08 |
CN110291720A (en) | 2019-09-27 |
DE102016225044A1 (en) | 2018-06-14 |
WO2018108216A1 (en) | 2018-06-21 |
US10700698B2 (en) | 2020-06-30 |
JP2020502919A (en) | 2020-01-23 |
CN110291720B (en) | 2023-07-21 |
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