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    • 专利摘要:
    Device for measuring electrical magnitudes of analog sensors where a controller (3) connected to a network of capacitances (1), and an interface circuit (2) connected to an analog sensor (21), and wherein said network of capacitances (1) ): it is connected to said interface circuit (2) connected to the analog sensor (21); it comprises at least two electric capacitors (11) of known value, wherein the ratio of the capacitance between at least two of said electric capacitors (11) is at least 10: 1. This device is applicable to the measurement of electrical voltages of analog sensors based on a change in capacitance, electrical resistance or inductance, or that directly generate an electric current or a voltage. The invention also comprises the associated measurement method. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2540154A1
    申请号:ES201431631
    申请日:2014-11-07
    公开日:2015-07-08
    发明作者:Jorge Eliécer GAITÁN PITRE；Ramón Pallàs Areny
    申请人:SEAT SA；
    IPC主号:
    专利说明:

    DESCRIPTION

    Device and method for measuring electrical quantities of analog sensors

     5
    OBJECT OF THE INVENTION

    The purpose of the present patent application is a device and method for measuring electrical quantities of analog sensors according to claims 1 and 11, which incorporates notable innovations and advantages. 10

    The present invention relates, in general, to analog sensor measurement systems, including those that directly generate an electric current or voltage.
     fifteen

    BACKGROUND OF THE INVENTION

    The output signal of the analog sensors is usually a low amplitude electrical voltage generated by the sensor, or by an interface circuit that incorporates one or more 20 sensors and, if necessary, one or more voltage or electric current sources . The methods proposed in the state of the art for measuring said output voltage or current of the analog sensors, or their interface circuits, are numerous and currently all of them are pursuing a digital output, which can be achieved directly or hint. 25

    The direct obtaining of a digital output from the voltage generated by the sensor, or by the interface circuit to which the sensor is connected to obtain an analog output voltage, is achieved by means of an analog to digital voltage converter (converter A / D or CAD), which may be a specific integrated circuit, or a circuit embedded in another multifunctional circuit 30, such as a digital controller. The output of said analog-digital converter is digitally processed to extract the desired information, or to make a decision. To adapt the output signal of the sensor, or its interface circuit to the range of input amplitudes of the A / D converter, a signal conditioning circuit is added that includes at least one component capable of amplifying voltages or currents. 35

    Interface circuits for resistive sensors are usually based on voltage dividers, for example when the change in resistance relative to their initial value is large, or in circuits derived from the voltage divider, for example when the change in resistance relative to their value Initial is small. Wheatstone bridges and pseudo-continuous bridges, such as those described, for example, in US3130578 and in EP1397654 and US20130249574, can be considered as interface circuits derived from the voltage divider.

    The interface circuits for capacitive or inductive sensors may also be based on voltage dividers, or consist of bridges powered by an alternating voltage or resonant circuits, such as those described for example in US2932970, and in the application for US20130271158. Resistive sensors can also be incorporated into resonant circuits.
     fifteen
    Analog sensors based on a variation of resistance, capacity or inductance can be simple or differential. In the first case they are modeled as a single electronic component that changes with the measured variable, while the second ones are modeled as two electronic components that have a common node, and in which the measured variable causes a change of the same magnitude but of opposite way. twenty

    In general, voltage dividers can include a single sensor or a differential sensor, while bridges (continuous or alternating) can include one, two, three or four variable impedance sensors, or several sensors connected in series combinations and in parallel, which are arranged in one, two, three or four arms of the bridge. The voltage dividers 25 have at least three connection terminals with the signal conditioning circuit required by the A / D converter: an excitation voltage is applied between two terminals and the voltage between the third terminal and one of the two is measured. previous terminals. The sensor jumpers, on the other hand, have at least four terminals, which are usually connected in pairs: bridge 30 is excited through a pair by means of an electrical voltage or current, and with the other pair the voltage or current of the exit.

    Thus, the conventional method for measuring electrical quantities of analog sensors directly is to arrange them in a circuit that obtains a related electrical voltage 35
    with the magnitude detected by the sensor, and digitize said voltage with an analog-digital converter (CAD).

    Alternatively, sensors based on a resistance or capacity variation can be placed in a circuit that generates a signal whose duration depends on the value of the magnitude detected by the sensor. To have a digital output, it is enough to measure the duration of that signal, for which a clock signal is needed, being then a cheaper process than an analog-digital converter (CAD).

    Automotive component manufacturers offer integrated solutions to measure 10 physical and chemical parameters that include a sensor element and the electronic circuits needed to provide a standardized electrical output (e.g. for a CAN bus). If the electrical output is not normalized, the sensor is connected to its own control unit (ECUs, control units) that usually accept several sensors. An example would be the electronic circuits that are connected to a sensor element to measure the steering wheel angle. However, there are currently many other sensors in the car that could benefit from the development of the invention. Some of these could be:

    1. Position sensors and rotation angle. They are based on the change of electrical resistance of an angular or linear potentiometer, or on the change of electrical resistance of a magnetoresistance. They are used to measure, for example: the position of the accelerator pedal, the travel and position of the suspension, the position of the butterfly valves, and the position of the probe plate in the injection system.

    In the following patents it can be seen that many manufacturers continue to propose 25 solutions based on the conventional signal conditioning and digitization structure obtained by the sensor element: "US844125282. Measuring device for angle of rotation. ”,“ DE102006032266A1. Sensor component. ”,“ DE60218016D1. Electric power steering. ”, And“ DE102009032664A1. Accelerator pedal for motor vehicles: ”.
     30
    2. Absolute and differential pressure sensors. They are based on changes in electrical resistance due to mechanical deformation. They are used to measure the pressure of: fuel, brake fluid, oil, and coolant.

    Also for these sensors, solutions based on the conventional measurement structure described above are still proposed in the patents of several manufacturers.

    In addition, and according to the desired accuracy and resolution, the signal conditioning circuits prior to the A / D converter, and which are connected to the sensor interface circuit, 5 may need: voltage transformers; active components, such as operational or instrumentation amplifiers, and voltage comparators; complex manual or automatic adjustments.
    These components and procedures increase the cost of the final product to a value that may be excessive for certain applications or fields of application. 10

    In summary, the analysis of existing information to date shows that current methods for measuring electrical quantities of analog sensors suffer from one of these limitations: (a) the need for an analog-digital converter and the (active) conditioning circuit to adapt the output voltage of the interface circuit or sensor to the range of input amplitudes of the analog-digital converter; (b) the need for a digital counter and a clock signal whose frequency determines the resolution that will be taken in the measurement; and (c) the limited applicability to a type of sensors, for example of the transfer of charge to capacitive sensors.
     twenty
    Thus, there is still a need to have a device, and an associated method, for measuring electrical quantities of analog sensors based on a change in capacitance, electrical resistance or inductance, or that directly generate an electrical current or a voltage of the millivolt order This includes numerous sensors of temperature, lighting, position, proximity, displacement, force, pressure and other 25 usual quantities in automotive, and in other fields of the industry.

    DESCRIPTION OF THE INVENTION

    In accordance with the present invention, this task is solved by means of a device and method for measuring electrical quantities of analog sensors according to claims 1 and 11. Additional advantages of the invention are presented accompanying the features 5 included in the dependent claims mentioned in the Description outlined below.

    The object of the present patent application is a new method for measuring electrical quantities of analog sensors that are based on a change in electrical resistance 10 (resistive), capacitance (capacitive), or inductance (inductive), or that directly generate a current or an electrical voltage (generators). A second object is a device, based on said measurement method, employing: a network of capacitances of known value and switchable connections; a circuit that includes: at least one analog sensor and a passive interface circuit; and a digital controller. fifteen
    The proposed innovative solution is that the object of the present invention can be implemented using at least two electric capacitors and a controller, without the need for any other active electronic component apart from said controller.

    Thus, and more specifically, the device for measuring electrical quantities of analog sensors 20 comprises a controller, preferably digital, connected to a capacitance network, and an interface circuit connected to an analog sensor, wherein said capacitance network: is connected to said interface circuit connected to the analog sensor, comprises at least two electric capacitors of known value (or any other element with capacitive properties), wherein the capacitance ratio between at least two of said electric capacitors is at least 10: 1 .
    In this way, the connection of the interface circuit to the digital controller avoids the need for an external power supply, and makes it possible to obtain the current necessary to charge at least a first capacitor in the capacitance network. On the other hand, the proposed interface circuit uses fewer electronic components than currently available sensors 30, when connecting the sensor element directly to the microcontroller, without the need for intermediate integrated circuits for processing and digitizing the signal offered by the sensor element . You only need some passive component (resistors, electrical capacitors ...). This absence of active components and the
    Lower number of passive components required lead to lower cost and greater reliability.

    According to another aspect of the invention, the interface circuit and the capacitance network and the controller comprise at least one connection pin, wherein the interface circuit 5 comprises at least one passive analog circuit between the pin connecting said interface circuit with the network capacitance, and at least one of the pins that connect said interface circuit to the controller. Analog passive circuit means a purely resistive circuit, as a voltage divider, but it can also be an RC, RL or R circuit in parallel with a photodiode. The sensor, and the calibration elements, are in parallel with a resistor.

    As a consequence, the at least one analog passive circuit is composed of a plurality of passive electronic components, these being able to be resistive, capacitive, inductive elements; or combined among them, RC or RL, optionally including 15 photodiodes. In this way, various circuit implementation alternatives are offered, as well as the possibility of measuring sensors with a differentiated main electrical property, either resistive, well capacitive, or inductive. It also allows the measurement of graduations and light intensities with a photodiode.
     twenty
    In an alternative embodiment of the invention, the interface circuit comprises a Wheatstone bridge in which at least one of the components of each of the arms is the analog sensor, said Wheatstone bridge being connected to a plurality of passive electronic components. With this modality an alternative configuration to the series-parallel arrangement of the electrical components is established, and the advantages of the Wheatstone bridge layout are taken advantage of.

    According to the principle of operation of the device, the interface circuit is powered from at least one of the input / output pins of said controller. In this way, an additional and independent power supply is not necessary, but the outputs of the controller itself are used.

    According to another aspect of the invention, the preferably digital controller comprises a memory with a plurality of codes corresponding to the different ranges of values of the measured magnitude. In this way some measuring ranges are established, and by 35
    comparison, it is determined in which of them the measurement is made, determining the corresponding output information of the controller in a predetermined format and / or values.

    On the other hand, the capacitance network comprises at least one switchable connection between at least two electrical capacitors of known values. Thus, it is possible to optionally remove specific components from the circuit, either by bridging them or by disconnecting them from the circuit by leaving at least one of their terminals in the air.

    It should be mentioned that, in a preferred embodiment of the invention, the ratio of the capacitance between at least two of said electric capacitors is at least 100: 1. In this way it is possible to establish a greater precision in the measurement when a greater number of redistribution cycles of load for the same measure is necessary.

    In another preferred embodiment of the invention, the capacitance ratio between at least two of said electric capacitors is at least 1,000: 1. In this way it is possible to establish an even greater precision in the measurement as a greater number of redistribution cycles of load for the same measure is necessary.

    In yet another preferred embodiment of the invention, the capacitance ratio between at least two of said electric capacitors is at least 10,000: 1. In this way it is possible to establish an even greater precision in the measurement as a greater number of redistribution cycles of load for the same measure is necessary.

    The method for measuring electrical quantities of analog sensors, comprising the following steps, is also the subject of the present patent application:
    a) generate a voltage on the analog sensor and / or on the interface circuit to which it is connected.
    b) charging with said voltage at least a first electric capacitor of said capacitance network, based on switching the connections between the controller, the 30 capacitance network, and the analog sensor and / or the interface circuit.
    c) redistributing the charge accumulated in said first electric capacitor in at least a second electric capacitor of said capacitance network, by switching the connections between the controller and the capacitance network.
    d) repeat steps a), b) and c) until the terminal voltage of said second capacitor of the capacitance network reaches a preset voltage threshold.

    This method does not need an analog-digital converter (CAD), or any time meter, but a simple event counter. It is based on using a capacitance network 5 comprising at least two electric capacitors of known value, one of which is much larger than the other. To measure the voltage generated by the circuit that incorporates the sensor, at least one of the two capacitors is charged with said voltage, and then the load on them is redistributed. The process is repeated until the terminal voltage of at least one of the capacitors reaches a preset voltage threshold VT. 10 The number N of repetitions of the charge redistribution process then depends on the relationship between the capacities of the two capacitors, the preset threshold and the voltage of the circuit that incorporates the sensor. To increase the value of N, and thus improve the resolution of the method, the charging time of the small capacitor can be limited so that it is not fully charged. fifteen

    All switching functions of the connections between capacitors, compared with a voltage threshold, control of the charging time and counting events, can be performed with a simple low-cost microcontroller, which offers a standard digital output. twenty

    Indirectly obtaining a digital output from the changes experienced by the sensor in terms of the magnitude it detects is to deduce the value of this magnitude from a model (eg a formula) that relates its value to that of another magnitude of a different nature, but that is not a voltage or electric current, and that is related to that magnitude of interest. This method is therefore capable of obtaining a digital output without the need for voltage digitizing devices, that is, without an A / D converter.

    The transfer of charge from an unknown capacitor (sensor) to another capacitor of known value is a common procedure for measuring electrical quantities of capacitive sensors that are charged to a known voltage. The method described in this patent is different because: (a) a capacitance network is needed comprising at least two capacitors of known value (or any other element with capacitive properties) such that the relationship between their capabilities is known, while the known procedures of charge transfer the capacity of a capacitor 35 is determined
    unknown; (b) the voltage Vx necessary to load the elements of the capacitance network is not a known voltage (as in the known procedures of load transfer) but is generated by the sensor or by a circuit where the sensor is connected to components liabilities; and (c) the voltage that when it reaches the VT value determines the completion of the process is not the voltage at terminals of a specific capacitor 5, but is that obtained at terminals of at least two capacitors of the capacitance network that depends on the structure of this network. These differences make it possible to obtain at least four advantages that the known methods of charge transfer used so far to measure electrical quantities of capacitive sensors lack: (1) the method can be applied to both capacitive, resistive, inductive sensors, or 10 voltage or current generators; (2) the resolution can be improved by controlling the time during which the voltage Vx is applied to one or more elements of the capacitance network; (3) the resolution can also be improved by detecting a voltage drop instead of a voltage surge, for example at terminals of a capacitor; and (4) voltage detection at terminals of at least two capacitors in the capacitance network can be performed on a low ground impedance node, and thus reduce the effects of capacitive interference.

    Advantageously, the controller limits the charging time of the first electric capacitor of said capacitance network, so that said first electric capacitor is not fully charged. In this way, (limiting for example the charging time of the small capacitor) increases the value of N, and thus improves the resolution of the method.

    The principle of operation of the method is that the controller counts the number of cycles necessary to achieve a certain voltage in terminals of said second electric capacitor, based on successively redistributing a specific amount of charge of the first electric capacitor in said second capacitor electric. In this way it is possible to perform a measurement as easily as counting a number of loading and unloading cycles.
     30
    According to another aspect of the invention, the controller determines the measurement of the electrical magnitude of the analog sensor by comparing the number of times the load redistribution is repeated, with a series of codes previously stored in a memory of said controller, corresponding to different intervals. of measured magnitude values. In this way, measuring ranges are established, and by comparison 35
    determine in which of them the measurement is carried out, determining the corresponding output information of the controller in a predetermined format and / or values.

    According to yet another aspect of the invention, the controller determines the measure of the electrical magnitude by comparing the number of times the load redistribution is repeated, with a series of codes previously stored in a memory of said controller, corresponding to coefficients of a calibration curve of at least one passive electronic reference component. In this way, and by means of a simple calculation, the measured quantity is reached during the measurement processing.
     10
    The attached drawings show, by way of non-limiting example, a device for measuring electrical quantities of analog sensors, constituted according to the invention. Other features and advantages of said device, and of the associated method, for measuring electrical quantities of analog sensors, object of the present invention, will be apparent from the description of a preferred but not exclusive embodiment, which is illustrated by way of non-limiting example in the accompanying drawings, in which:


    BRIEF DESCRIPTION OF THE DRAWINGS 20

    Figure 1.- Shows a block diagram of the proposed device, in accordance with the present invention;
    Figure 2a.- Shows a first possible embodiment of the capacitance network, in accordance with the present invention; 25
    Figure 2b.- Shows a second possible embodiment of the capacitance network, in accordance with the present invention;
    Figure 2c.- Shows a third possible embodiment of the capacitance network, in accordance with the present invention;
    Figure 3.- Shows a preferred embodiment of the apparatus proposed in Figure 1, wherein the interface circuit comprises a simple resistive sensor Rx connected to other passive components, in accordance with the present invention;
    Figure 4.- Shows a table that summarizes the logical state of the controller pins during the sequence of operations to measure Rx in the preferred embodiment in Figure 3, in accordance with the present invention; 35
    Figure 5.- Shows a preferred embodiment of the device proposed in Figure 1, where the interface circuit comprises a simple capacitive sensor Cx connected to other passive components, in accordance with the present invention;
    Figure 6.- Shows a table that summarizes the logical state of the controller pins during the sequence of operations to measure Cx in the preferred embodiment in Figure 5 5, in accordance with the present invention;
    Figure 7.- Shows a preferred embodiment of the apparatus proposed in Figure 1, wherein the interface circuit comprises a simple inductive sensor Lx connected to other passive components, in accordance with the present invention;
    Figure 8 shows a preferred embodiment of the apparatus proposed in Figure 1, wherein the interface circuit comprises four simple resistive sensors (R3, R4, R5, and R6) connected to form a Wheatstone bridge 23, in accordance with the present invention;
    Figure 9.- Shows a preferred embodiment of the apparatus proposed in Figure 1, wherein the interface circuit comprises a photodiode (sensor) D connected to other passive components, in accordance with the present invention; fifteen
    Figure 10.- Shows a table that summarizes the logical state of the controller pins during the sequence of operations to measure D in the preferred embodiment in Figure 9.


    DESCRIPTION OF A PREFERRED EMBODIMENT 20

    In view of the aforementioned figures and, according to the numbering adopted, an example of a preferred embodiment of the invention can be observed therein, which comprises the parts and elements indicated and described in detail below. 25
    Thus, as seen in Figure 1 and 3, the device for measuring electrical quantities of analog sensors comprising a controller 3 connected to a capacitance network 1, and an interface circuit 2 connected to an analog sensor 21, characterized in that said capacitance network 1: it is connected to said interface circuit 2 connected to the analog sensor 21, it comprises at least two electric capacitors 11 of known value, in which the ratio of the capacitance between at least two of said electric capacitors 11 is at least 10 :one.

    Specifically, the device conceived is based on a digital controller 3 to which a capacitance network 1 and an interface circuit 2 connected to at least one 35 are connected.
    analog sensor 21, where appropriate, to passive components 24. Figure 1 is a block diagram of the proposed measuring device, where the capacitance network 1 comprises at least two capacitors 11 of known value (one of them much larger than the other) and switchable connections 13; digital controller 3 has a finite number (m) of input / output (I / O) pins (P1, P2, ... Pn, Pn + 1, Pn + 2, ..., Pm) to which several are connected nodes of the capacitance network 1 and the interface circuit 2. The internal structure of the circuit connected to these I / O pins allows three logical states to be established: (a) output at “0”; (b) output at "1"; and (c) input or state of high input impedance (HZ), which is a state appropriate to the magnitude to be detected (voltage) and that can be enabled to interrupt the measurement process when a given 10 is reached tension level The I / O voltage levels on each of these pins depend on the microelectronic technology in which the digital controller 3 is manufactured. Each of these logic states is necessary for the digital controller 3 to perform network connection functions. of capacitances 1 and in the interface circuit 2, a control of the charging time, a count of the charging cycles, and a comparison with a threshold of 15 voltage; all without the need for voltage or time measurement circuits, embedded in the digital controller 3 or external to said digital controller 3. The digital controller 3 can also be used for other functions, such as storing, representing or communicating the readings of the measurement, jointly or separately, regardless of the sensor or element being measured. twenty

    Figures 2a, 2b and 2c show three possible embodiments of the capacitance network 1, hereinafter: network 1 (figure 2a), network 2 (figure 2b), and network 3 (figure 2c). Network 1 consists of three capacitors C1, C2, and C3, connected C1 and C2 in series, and C3 in parallel with the serial connection of C1 and C2. The network 2 consists of two capacitors C1 and C2 connected in series. The network 3 consists of four capacitors C1, C2, C3 and C4 connected as follows: C1 and C2 connected in series with each other, C3 and C4 connected in parallel with each other and also in parallel with the serial connection of C1 and C2. In each of these embodiments: a) the capacitors have a known value relationship; b) C1 is much larger than the other capacitors; c) the node or pin 12 connects the capacitance network 1 to the interface circuit 2; d) the rest of the nodes or pins 12, according to the embodiment, connect the capacitance network 1 to the digital controller 3; and e) the comparison with the preset voltage threshold can be made on the first three nodes or pins 12 on the left (P1-P3), which allows, first, that the detection be made at a point of low impedance, and thus reduce the effects of capacitive interference, and second, that the threshold margin of 35
    voltage is greater if voltage drop is detected instead of an increase in voltage. These embodiments are simple examples to facilitate the understanding of the invention patent, but are not exhaustive as to the detail of the circuits.

    Additionally, as seen in Figures 3, 5, 7 and 9, the interface circuit 2 and the 5 capacitance network 1 and the controller 3 comprise at least one pin 12, 25, 33 of connection 13, 26, 34, and wherein the interface circuit 2 comprises at least one passive analog circuit 22 between pin 12, 25 that connects said interface circuit 2 with the capacitance network 1, and at least one of the pins 25, 33 that connect said interface circuit 2 with controller 3. In a preferred embodiment of the invention, controller 3 will have 4 pins 33 for 10 to be connected to interface circuit 2 and / or to capacitance network 1.

    It should be mentioned, as can be seen in Figures 3, 5, 7 and 9, that the at least one analog passive circuit 22 is composed of a plurality of passive electronic components 24. 15

    On the other hand, as shown in Figure 8, the interface circuit 2 comprises a Wheatstone bridge 23 in which at least one of the components 23a of each of the arms is the analog sensor 21, said Wheatstone bridge being 23 connected with a plurality of passive electronic components 24. 20

    According to another aspect of the invention, as seen in Figures 1, 3, 5, 7 and 9, the interface circuit 2 is fed from at least one of the input / output pins 33 of said controller 3.
     25
    According to a preferred embodiment of the invention, as seen in Figures 1, 3, 5, 7 and 9, the controller 3 comprises a memory 31 with a plurality of codes 32 corresponding to the different ranges of values of the measured magnitude .

    More particularly, as seen in Figures 2a, 2b and 2c, the capacitance network 1 30 comprises at least one switchable connection 13 between at least two electric capacitors 11 of known values.

    According to a preferred embodiment of the invention, the capacitance ratio between at least two of said electric capacitors 11 is at least 100: 1. 35

    According to another preferred embodiment of the invention, the capacitance ratio between at least two of said electric capacitors 11 is at least 1,000: 1.

    According to yet another preferred embodiment of the invention, the capacitance ratio between at least 5 of said electric capacitors 11 is at least 10,000: 1.

    The method of measuring electrical quantities of analog sensors 21 comprising the following steps is also an object of the invention:
    a) generate a voltage on the analog sensor 21 and / or on the interface circuit 2 to which it is connected.
    b) charging with said voltage at least a first electric capacitor 11 of said capacitance network 1, by switching the connections between the controller 3, the capacitance network 1, and the analog sensor 21 and / or the interface circuit 2.
    c) redistributing the accumulated charge in said first electric capacitor 11 to at least 15 a second electric capacitor 11 of said capacitance network 1, by switching the connections between controller 3 and capacitance network 1.
    d) repeat steps a), b) and c) until the terminal voltage 11a of said second capacitor 11 of the capacitance network 1 reaches a predetermined voltage threshold. twenty

    Thus, said method consists in counting the number of cycles necessary to achieve a certain voltage VT in a capacitance network 1 based on redistributing (successive times) a specific amount of load between its elements; load that is obtained when connecting one or more of these elements, during a programmable time, to an unknown voltage 25 Vx generated by the interface circuit 2, which includes: 1) at least one analog sensor and 2) a passive interface circuit ; both connected to the digital controller 3. The shorter said Vx connection to the capacitance network 1, the lower the accumulated load on the components of said network, and the greater the number of times the process will have to be repeated, so which will improve the resolution of the measure. Said network of 30 capacitances 1 requires at least two capacitors 11 (or another element with capacitive properties), one of which must have a capacitance much greater than the others, and switchable connections. The number N of times the load redistribution process is repeated depends on the relationship between the elements of the capacitance network 1 and the voltage VT; therefore, to determine the change experienced by the sensor 35
    analog 21 just know the value of these parameters. The method can be implemented by a digital controller 3, without the need for any other external active electronic component or embedded in the controller 3 itself, such as an analog-digital converter or a circuit for measuring time by means of a clock signal and a counter of voltage pulses. 5

    The measured quantity is determined by comparing the number N of times the load redistribution process is repeated with a series of digital codes, corresponding to different ranges of values of the measured quantity, said digital codes being arranged in a table. Another way to determine the measured magnitude 10 is to measure one or more passive reference elements to generate the coefficients of a calibration curve and obtain the measured magnitude by calculation. Said table and the coefficients of the calibration curve are stored in the memory 31 of the digital controller 3 for use during the measurement processing.
     fifteen
    The exposed measurement method can be carried out in different ways, which involve a different number of elements and interconnections in the capacitance network 1 and in the interface circuit 2. Whatever the form, the sequence of operations performed by the controller digital 3, the method consists of at least three stages: a first stage to zero any load in the capacitance network 1; a second stage to apply to 20 the capacitance network 1 the voltage generated by the interface circuit 2, where the sensor 21 is; and a third stage to redistribute between one or more elements of the capacitance network 1 the electric charge contributed in the previous stage. Some of these sequences of operations are described at the end of the report, in the preferred embodiments of the proposed measuring device. 25

    It is worth mentioning that the capacitance network is made up of at least two capacitances, one of them much larger than the others. It should be noted, however, that the second stage is not necessarily to charge the least of the capacitance but one of them. A voltage threshold can be detected on at least two nodes or pins 12 different from the capacitance network 30 1. Therefore, the voltage at the capacitance terminals of the highest value is not always measured.

    As an example, in Figure 2b, C1 is the largest capacitance, and it is charged to the voltage between its terminals, which depends on the output voltage of the analog sensor 21 and / or the interface circuit 2 to which it is connected .

    According to another aspect of the invention, the controller 3 limits the charging time of the first electric capacitor 11 of said capacitance network 1, so that said first electric capacitor 11 is not fully charged.

    Thus, the number N of repetitions of the process of redistribution of charge then depends on the relationship between the capacities of the two capacitors, the preset threshold and the voltage of the circuit that incorporates the sensor 21. To increase the value of N, and thus improve the resolution of the method, the charging time of the small capacitor can be limited so that it is not fully charged.

    An example of a mathematical formula of this relationship follows, although there is no single mathematical formula that fits each of the proposed preferred embodiments. Each equation depends on the components that form the interface circuit and the sensor 21. The equation shown applies to obtain Nx in the circuit of Figure 3.

     20  RRRxRC1C3-TRx R C1C2C3C2C32RRxln1-VTVOH1-RxRNxC1lnC1C2C1C3e

    where VOH is the output voltage of the fourth pin on the left of the controller 3 during the charging stage, VT is the threshold voltage of the pin, and T is the time during which the fourth pin maintains the voltage VOH.
     25
    More specifically, the controller 3 counts the number of cycles necessary to achieve a certain voltage at terminals 11a of said second electric capacitor 11, based on successively redistributing a specific amount of charge of said first electric capacitor 11 on said second electric capacitor 11 .
     30
    According to another aspect of the invention, the controller 3 determines the measure of the electrical magnitude of the analog sensor 21 by comparing the number of times the load redistribution is repeated, with a series of codes 32 previously stored in a memory 31 of said controller 3 , corresponding to different ranges of values of the measured magnitude. 5

    According to yet another aspect of the invention, the controller 3 determines the measure of the electrical magnitude by comparing the number of times the load redistribution is repeated, with a series of codes 32 previously stored in a memory 31 of said controller 3, corresponding to coefficients of a calibration curve of at least 10 passive electronic reference component 24.

    Five preferred embodiments of the invention are described below, where: (a) the interface circuit 2 comprises at least one analog sensor 21 and a passive reference element; (b) controller 3 is a very low cost common 8-bit microcontroller that 15 does not incorporate any analog-digital converter or other analog or digital peripheral circuits; (c) pins 33 are I / O pins (input / output) of controller 3, whose internal structure of these I / O pins 33 (input / output) allows three logical states to be established: (a) output at “0 ”, With an output voltage V0; (b) output "1", with an output voltage V1; and (c) input or HZ, which can be enabled to interrupt the measurement process when a certain voltage is achieved; (d) C1 and C2 are two electric capacitors of known value, whose ratio is 10,000: 1. In each of these embodiments the controller 3 performs a sequence of operations to measure the sensor 21 or a reference element. Thus, a number Ni of charge cycles for the sensor 21 or the measured reference element results. Hence, using the equation that for each interface circuit 2 relates 25 Vx to the value of the sensor 21, the measured magnitude value can be determined.

    Figure 3 shows a first preferred embodiment of the apparatus of Figure 1, where the capacitance network 1 is network 1 and the interface circuit 2 comprises a simple resistive sensor Rx and a resistor RR of known value, arranged in a voltage divider 30 resistive R1 and R2 are two reference resistors, known and stable, necessary to calculate the coefficients of a calibration curve and obtain Rx by calculation. C3 is a capacitor of known value, whose ratio with C1 is 100,000: 1. The sequence of operations performed by controller 3 to measure both Rx and R1 and R2 consists of three stages: (1) zeroing, (2) loading, and (3) redistribution and reading. The specific set of 35
    Operations to measure Rx is as follows. Initially, the first seven pins 33 (P1-P7) of the controller 3 are configured as HZ to prevent these pins 33 from being set up in any unwanted way when the system is started up. Then, in step (1), seven first pins 33 (P1-P7) are configured as output at "0"; therefore, any electrical charge accumulated in the elements of the interface circuit 3 is drained to ground. Then, 5 in stage (2), third and fifth pin 33 (P3, P5) remain in their previous state, while fourth pin 33 (P4) is set as output at “1” and first, second, third, sixth and seventh pin 33 (P1, P2, P3, P6 and P7) are configured as HZ; therefore, C2 is charging, and if fourth pin 33 (P4) is maintained in the "1" state (voltage V1) for a sufficiently long time with respect to the time constant Tc of the resulting RC circuit 10, it will finally reach the voltage Vx of the voltage divider formed by Rx and RR. If, on the other hand, fourth pin 33 (P4) is kept in the “1” state for a shorter time, the voltage at terminals of C2 will be a fraction of Vx, so that the load accumulated in it will be less. Note that with this pin arrangement, C3 is also charged to the voltage V2 resulting in the second pin 33, and C1 is charged to the voltage difference V12 at its terminals. 15 Finally, in stage (3), first, third, sixth and seventh pins 33 (P1, P3, P6 and P7) remain in their previous state, fourth and fifth pins 33 (P4 and P5) are configured as input, second pin 33 (P2) is set as output at “0”. With this new arrangement of pins 33, the accumulated load in C2 is redistributed with C1, and first pin 33 (P1) acts as a voltage comparator with TTL / CMOS threshold and high input impedance; 20 the result is an increase in voltage ΔVC1 at terminals C1 proportional to the redistributed load, and therefore to Vx, which in turn depends on Rx. Steps (2) and (3) are repeated until the voltage between terminals C1 is equal to or greater than the threshold voltage VT on first pin 33 (P1). The control program counts the load cycles necessary to reach said threshold, without the need for any timer or pulse counter of 25 voltage integrated in the controller 3. At the end of the sequence, a number Nx of load cycles related to the Impedance change of the sensor 21. Nx will be much higher, and therefore the measurement resolution will be better, the shorter the time during which the fourth pin 33 (P4) is maintained in the "1" state. An alternative to the previous sequence of operations is to detect the voltage drop ΔVC3 at terminals of C3 30 (on the second pin 33 P2), which depends on the load that accumulates in C1 during a previous measurement cycle. Thus, a voltage threshold can be detected in at least two different nodes or pins 12 of the capacitance network 1.

    Figure 4 is a table summarizing the logical state of the pins of controller 3 during a cycle of the sequence to measure Rx in the embodiment of Figure 3. The sequence of operations performed by controller 3 to measure R1 and R2 is similar. which is done to measure Rx; the difference is that pins 33 sixth and seventh (P6 and P7) perform, for each measurement, the function previously performed by pin 33 fifth (P5), while pins 33 5 that do not intervene in the measurement are configured as HZ . Thus, the Ni value of load cycles that results for each measured resistance is N1 and N2. Hence, using the equation that relates the voltage Vx of the interface circuit 2 with the value of Rx, Rx can be determined independently of VT and RR. The changes in these elements and parameters should not affect the measurement, but this depends on R1 and R2, which must be sufficiently stable.

    Figure 5 shows a second preferred embodiment of the apparatus of Figure 1, where the capacitance network 1 is network 3 and the interface circuit 2 comprises a simple capacitive sensor 21 Cx and a known RC resistor, arranged in an RC circuit. C4 and C5 are two reference capacitors 11, whose relationship between their capacities is known and stable, necessary to determine Cx. The sequence of operations performed by controller 3 to measure both Cx, C4 and C5 consists of four stages: (1) zeroing, (2) loading, (3) unloading and reading, and (4) redistribution. The specific set of operations to measure Cx is as follows. Initially, first seven pins 33 (P1-P7) are configured as HZ. Then, in step (1), seven first pins 33 (P1-P7) are set as output at "0". Then, in step (2), P7 remains in its previous state, P6 is configured as output at "1", and P1 to P5 are configured as HZ; this pin arrangement 33 is maintained for a sufficiently long time with respect to the time constant Tc of the RC circuit formed by Rc and Cx. Thus, Cx is charged through Rx at voltage V1 of P6. It should be noted that this stage of the measurement sequence is not to load the capacitance network 1, but to apply a fixed load to the sensor 21. Then, in step (3), P1, P3, P4, P5, and P7 remain in HZ, P2 and P6 are configured as output at “0” (voltage V0); therefore, Cx is discharged towards V0 and the network 3 is charged at a fraction of the discharge voltage Vx at the terminals of Cx. The duration of this arrangement 30 of pins must be sufficiently short with respect to Tc and determines the resolution that will be taken in the measurement. At this same stage, the voltage level between the terminals of C2 through P1 is detected and compared. Finally, in step (4), P2, P3, P4, P5 remain in their previous state, P1 is configured as output at "0", and P6 and P7 are configured as HZ. The steps (2), (3), and (4) are repeated until the voltage between the terminals of C2 is equal or 35
    higher than the threshold voltage VT P1. At the end of the sequence, a number Nx of load cycles related to the impedance change of the sensor 21 results. Note that the voltage VT is achieved between the terminals of C2 during the discharge-load stage (3). However, it could also be achieved between terminals C1 during the redistribution step (4). Figure 6 is a table summarizing the logical state of the pins of controller 3 during a cycle of the sequence for measuring Cx in the embodiment of Figure 5.

    The sequence of operations performed by controller 3 to measure C3 and C4 is similar to that performed to measure Cx; the difference is that pins 33 P4 and P5 perform, for each measurement, the function previously performed by pin P7, while pins 33 that do not intervene in the measurement are configured as HZ. Thus, the Ni value of load cycles that results for each measured resistance is N3 and N4. Hence, using the equation that relates the voltage Vx of the interface circuit 2 with Cx, Cx can be determined independently of VT and Rc.
     fifteen
    Figure 7 shows a third preferred embodiment of the apparatus in Figure 1, where the capacitance network 1 is network 1 and the interface circuit 2 comprises a simple inductive sensor 21 Lx and a known resistor RL, arranged in a circuit RL. L1 and L2 are two reference inductors, known and stable, necessary to determine Lx. The sequence of operations performed by the controller 3 to measure Lx, L1 and L2 is almost the same as 20 performed to measure, respectively, Rx, R1 and R2 in the preferred embodiment of Figure 3. It differs in that the time taken applied to load C2 to Vx is now determined by the time constant of the RL network.

    Figure 8 shows a fourth preferred embodiment of the apparatus in Figure 1, where the capacitance network 25 is network 2 and the interface circuit 2 comprises a maximum of four sensors 21 based on a change in resistance (R3, R4, R5 , and R6) connected forming a Wheatstone bridge 23, and a resistance RP of known value. Pin P1 is used as a measurement node. It is assumed that all sensors 21 undergo the same relative change in resistance x, which can be positive or negative. The sequence of operations 30 performed by the controller 3 to measure the change of relative x of each sensor 21 allows the interface circuit 2 to be analyzed as a set of voltage dividers formed, respectively, by RP and the equivalent resistors Req1, Req2, and Req3 views, each one, from P5, P6 and P7 to P1. Thus, x depends on the voltage drop in these voltage dividers. Following the sequence of operations to measure Rx described in 35
    First embodiment, but now using a different load path determined by the configuration of the three pins that connect the bridge with the controller 3, three different values of N are obtained. From here, using the equation that describes the value of the equivalent resistors Req1 , Req2, and Req3, x can be determined independently of VT and RP.
     5
    Figure 9 shows a fifth preferred embodiment of the apparatus in Figure 1, where the capacitance network 1 is network 2 and the interface circuit 2 comprises a photodiode D (sensor) and a known RF resistor, with a common node 25. The equivalent electrical circuit of the photodiode allows to analyze the circuit formed by D and RF as an RC circuit, whose time constant depends on the intensity of the incident electromagnetic radiation 10 on the photodiode. R7 and R8 are two known resistors that are used to control the time constant and thus improve the resolution in the measurement. The sequence of operations performed by controller 3 to measure the impedance variation experienced by D is similar to that performed by controller 3 to measure Cx in the preferred embodiment of Figure 5. The main differences are the pin arrangements 33 of 15 controller 3 and the time that is applied to charge C2 to Vx, which is now determined by the time constant of the circuit formed by D and RF.

    Figure 10 is a table summarizing the logical state of the pins of the controller 3 during a cycle of the sequence for measuring D in the embodiment of Figure 9, when D is polarized 20 in reverse through RF. The sequence of operations performed by controller 3 to measure D when polarized in reverse through R7 and R8 is similar to that performed through RF; the difference is that pins P6 and P7 perform, for each measurement, the function of pin P4, while pins that do not intervene in the measurement are configured as HZ. The measured quantity is determined by comparing the number N of times the load redistribution process is repeated with a series of digital codes, corresponding to different ranges of values of the measured quantity, arranged in a table in the control program of the controller 3.

    The above description of the preferred embodiments includes several specific details 30 of the invention that may facilitate its understanding, but it is not exhaustive either in terms of possible embodiments, or in the detail of the circuit where the sensor 21 is incorporated. Likewise, the details, shapes, dimensions and other accessory elements, as well as the components used in the implementation of said device, and associated method, for measuring electrical quantities of analog sensors 35
    they may be conveniently substituted by others that are technically equivalent, and do not deviate from the essentiality of the invention or the scope defined by the claims that are included following the following list.

    List of numerical references: 5

    1 capacitance network
    11 electric capacitor
    11th terminal (of the electric capacitor)
    12 pin (capacitance network) 10
    13 connection (capacitance network)
    2 interface circuit
    21 analog sensor
    22 analog passive circuit
    23 Wheatstone Bridge 15
    23rd component (Wheatstone bridge)
    24 passive electronic component
    25 pin (interface circuit)
    26 connection (interface circuit)
    3 controller 20
    31 memory
    32 code
    33 pin (controller)
    34 connection (controller)
     25

    List of references used as abbreviations of the text within the figures

    F11 Capacitance Network
    F12 Sensor and interface circuit 30
    F13 Digital Controller
    F41 Stage
    F42 Sequence to measure Rx
    F61 Stage
    F62 Sequence to measure Cx 35
    F101 Stage
    F102 Sequence to measure D
    权利要求:
    Claims (1)
    [1]

    1- Device for measuring electrical quantities of analog sensors comprising a controller (3) connected to a capacitance network (1), and an interface circuit (2) connected to an analog sensor (21), characterized in that said capacitance network ( fifteen
    - is connected to said interface circuit (2) connected to the analog sensor (21),
    - comprises at least two electric capacitors (11) of known value,
    wherein the capacitance ratio between at least two of said electric capacitors (11) is at least 10: 1.
     10
    2- Device according to claim 1 characterized in that the interface circuit (2) and the capacitance network (1) and the controller (3) comprise at least one connection pin (12, 25, 33) (13, 26, 34) , and wherein the interface circuit (2) comprises at least one passive analog circuit (22) between the pin (12, 25) that connects said interface circuit (2) with the capacitance network (1), and at least one of the pins (25, 33) that connect said interface circuit (2) with the controller (3).
    3- Device according to claim 2 characterized in that the at least one passive analog circuit (22) is composed of a plurality of passive electronic components (24).
     twenty
    4- Device according to claim 1 characterized in that the interface circuit (2) comprises a Wheatstone bridge (23) in which at least one of the components (23a) of each of the arms is the analog sensor (21), being said Wheatstone bridge (23) connected with a plurality of passive electronic components (24).
     25
    5- Device according to claim 1 characterized in that the interface circuit (2) is powered from at least one of the input / output pins (33) of said controller (3).
    6- Device according to claim 1, characterized in that the controller (3) comprises a memory (31) with a plurality of codes (32) corresponding to the different ranges of values of the measured quantity.
    7- Device according to claim 1 characterized in that the capacitance network (1) comprises at least one switchable connection (13) between at least two electrical capacitors (11) of known values. 35
    8- Device according to claim 1 characterized in that the capacitance ratio between at least two of said electric capacitors (11) is at least 100: 1.
    Device according to claim 1, characterized in that the ratio of capacitance 5 between at least two of said electric capacitors (11) is at least 1,000: 1.
    10. Device according to claim 1, characterized in that the capacitance ratio between at least two of said electric capacitors (11) is at least 10,000: 1.
     10
    11- Method for measuring electrical quantities of analog sensors according to claim 1 comprising the following steps:
    a) generate a voltage on the analog sensor (21) and / or on the interface circuit (2) to which it is connected.
    b) charging with said voltage at least a first electric capacitor (11) of said capacitance network 15 (1), by switching the connections between the controller (3), the capacitance network (1), and the analog sensor (21) and / or the interface circuit (2).
    c) redistributing the accumulated charge in said first electric capacitor (11) in at least a second electric capacitor (11) of said capacitance network (1), by switching the connections between the controller (3) and the capacitance network (one). twenty
    d) repeat steps a), b) and c) until the terminal voltage (11a) of said second capacitor (11) of the capacitance network (1) reaches a preset voltage threshold.
    12. Method according to claim 11, characterized in that the controller (3) limits the charging time of said first electric capacitor (11) of said capacitance network (1), so that said first electric capacitor (11) is not completely left loaded.
    13. Method according to claim 11, characterized in that the controller (3) counts the number of cycles necessary to achieve a certain terminal voltage (11a) of said second electric capacitor (11), based on successively redistributing a specific amount of charging said first electric capacitor (11) in said second electric capacitor (11).
    14. Method according to claim 13, characterized in that the controller (3) determines the measurement of the electrical magnitude of the analog sensor (21) by comparing the number of times the load redistribution is repeated, with a series of codes (32) previously stored in a memory (31) of said controller (3), corresponding to different ranges of values of the measured magnitude. 5
    15. Method according to claim 13, characterized in that the controller (3) determines the measure of the electrical magnitude by comparing the number of times the load redistribution is repeated, with a series of codes (32) previously stored in a memory (31) of said controller (3), corresponding to coefficients of a calibration curve 10 of at least one passive electronic component (24) of reference.
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    同族专利:
    公开号 | 公开日
    EP3018484A1|2016-05-11|
    ES2540154B2|2016-02-22|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20090125179A1|2007-11-09|2009-05-14|Spx Corporation|Method and apparatus for monitoring battery drain and starter current|
    US20110148393A1|2009-12-18|2011-06-23|Kinects Solutions Inc.|System and device for measuring voltage in a conductor|
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    DE102004006020A1|2004-02-06|2005-08-25|E + E Elektronik Ges.M.B.H.|Circuit arrangement for capacitive humidity measurement and method for operating the same|
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    DE102012207430A1|2012-05-04|2013-11-07|Robert Bosch Gmbh|Circuit arrangement for measuring a sensor element capacitance|CN108226618B|2016-12-14|2020-06-30|中国航空工业集团公司西安航空计算技术研究所|Method for realizing power supply, acquisition and detection of sensor through interface configuration circuit|
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    EP15382518.7A| EP3018484A1|2014-11-07|2015-10-22|Device and method for measuring electrical variables of analog sensors|
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