Sensing system using current steering bridge

Abstract

Embodiments described herein relate to a system having a processor and a bridge circuit. The bridge circuit includes a pair of differential voltage sources, a first pair of sensing elements, and a second pair of sensing elements. The first pair of sensing elements generates a pair of measurement signals. The pair of measurement signals are independent of each other and based on corresponding sensing elements. The second pair of sensing elements are communicatively coupled to the first pair of sensing elements. The second pair of sensing elements defines a first divider. The pair of measurement signals are input into corresponding second sensing elements of the second pair of sensing elements. The first divider is configured to output a first output signal to the processor. The first output signal is a first differential signal of the first pair of sensing elements.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. patent application serial number 16 / 670,613, filed on October 31, 2019, entitled “Sensing Systems Using Current Steering Bridges,” the contents of which are incorporated herein in their entirety pursuant to 35 U.S.C. §119(e). Technical Field

[0003] The present disclosure relates to electronic circuits and systems, and more particularly, the present disclosure relates to sensing circuits for detecting fluid, pressure, and / or force changes. Background Art

[0004] Of the many types of sensors used in automotive applications, level sensors are one of the simplest in shape and size. For example, other sensors require a float mechanism or a series of switches that switch when the liquid level rises or falls. Instead of requiring a float mechanism or a series of small switches, level sensors simply implement a printed pattern of electrodes on a common PCB, making them simple and compact to design and implement. Capacitive sensors are based on changes in capacitance within a given system, inductive sensors are based on changes in inductance within a given system, and resistive sensors are based on changes in impedance within a given system. As the liquid level within the system changes, the amount of capacitance, inductance, and / or impedance increases or decreases.

[0005] However, despite their simplicity in design and application, conventional capacitive, inductive and / or resistive level sensors have several problems. For example, conventional capacitive, inductive and / or resistive sensors have a higher noise floor than any other type of implementation because the source impedance of the capacitive, inductive and / or resistive sensors is very high, making EMC design very difficult. Therefore, the incoming noise cannot be easily filtered out due to the high source impedance. The high source impedance causes the output of the sensor to have a high noise level and become unstable. For example, the impedance of a single capacitor, inductor and / or resistor powered by a DC power supply is essentially infinite. Therefore, the frequency is traditionally driven at a frequency in the range of 10Khz.

[0006] Therefore, a sensor having the versatility of using a sensor driven by high RF frequencies, as well as providing accurate fluid, pressure and / or force level measurements is desired. Summary of the invention

[0007] In one aspect, a system having a processor, a first bridge circuit, and a second bridge circuit is provided. The first bridge circuit is communicatively coupled to the processor. The first bridge circuit has a first pair of differential voltage sources and a first pair of capacitors configured to drive the first bridge circuit. The first pair of capacitors generates a first pair of measurement signals. One of the first pair of capacitors is positioned to contact a first measurable medium. The first pair of measurement signals are independent of each other and based on the output of the corresponding capacitors. The second bridge circuit is communicatively coupled to the processor. The second bridge circuit has a second pair of differential voltage sources and a second pair of capacitors configured to drive the second bridge circuit. The second pair of capacitors generates a second pair of measurement signals. One of the second pair of capacitors is positioned to contact a second measurable medium. The second pair of measurement signals are independent of each other and based on the output of the corresponding capacitors. The first bridge circuit outputs a first output signal to a divider, and the second bridge circuit outputs a second output signal to the divider. The divider generates a ratiometric output signal. The ratiometric output signal is determined by the processor as a ratio of the first output signal to the second output signal.

[0008] On the other hand, a system having a processor, a first bridge circuit and a second bridge circuit is provided. The first bridge circuit is communicatively coupled to the processor. The first bridge circuit has a first pair of differential voltage sources and a first pair of inductors configured to drive the first bridge circuit. The first pair of inductors generates a first pair of measurement signals. One of the first pair of inductors is positioned to contact a first measurable medium. The first pair of measurement signals are independent of each other and based on the output of the corresponding inductors. The second bridge circuit is communicatively coupled to the processor. The second bridge circuit has a second pair of differential voltage sources and a second pair of inductors configured to drive the second bridge circuit. The second pair of inductors generates a second pair of measurement signals. One of the second pair of inductors is positioned to contact a second measurable medium. The second pair of measurement signals are independent of each other and based on the output of the corresponding inductors. The first bridge circuit outputs a first output signal to a divider, and the second bridge circuit outputs a second output signal to the divider. The divider generates a ratiometric output signal. The ratiometric output signal is determined by the processor as a ratio of the first output signal to the second output signal.

[0009] In yet another aspect, a system having a processor, a first bridge circuit, and a second bridge circuit is provided. The first bridge circuit is communicatively coupled to the processor. The first bridge circuit has a first pair of differential voltage sources and a first pair of resistors configured to drive the first bridge circuit. The first pair of resistors generates a first pair of measurement signals. One of the first pair of resistors is positioned to contact a first measurable medium. The first pair of measurement signals are independent of each other and based on the output of the corresponding resistors. The second bridge circuit is communicatively coupled to the processor. The second bridge circuit has a second pair of differential voltage sources and a second pair of resistors configured to drive the second bridge circuit. The second pair of resistors generates a second pair of measurement signals. One of the second pair of resistors is positioned to contact a second measurable medium. The second pair of measurement signals are independent of each other and based on the output of the corresponding resistors. The first bridge circuit outputs a first output signal to a divider, and the second bridge circuit outputs a second output signal to the divider. The divider generates a ratiometric output signal. The ratiometric output signal is determined by the processor as a ratio of the first output signal to the second output signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Reference will now be made in conjunction with reading the following detailed description to the accompanying drawings, wherein like reference numerals refer to like parts throughout the several views, and wherein:

[0011] Figure 1A schematically depicts a circuit diagram of a pair of anti-phase voltage sources implemented by a differential LC oscillator according to one or more embodiments shown and described herein;

[0012] Figure 1B schematically depicts a current steering bridge circuit with a bias voltage, wherein a sensor capacitor is connected to an inverting voltage source, according to one or more embodiments shown and described herein;

[0013] Figure 1C Schematically depicts a pair of sine and cosine signals derived from a pair of current steering bridge circuits for use with a signal processor also suitable for inductive sensor applications in accordance with one or more embodiments shown and described herein;

[0014] Figure 2 schematically depicts a capacitive current steering bridge circuit according to one or more embodiments shown and described herein, wherein the source voltage is equal to zero and indicates that the output voltage is proportional to the differential capacitance about zero;

[0015] Figure 3 schematically depicts a linear ratiometric output of a three-port transducer according to one or more embodiments shown and described herein;

[0016] Figure 4schematically depicts a quadrature ratiometric output of a four-port transducer according to one or more embodiments shown and described herein;

[0017] Figure 5A Schematically depicts a variable capacitor of a capacitive voltage divider having an I phase on a first layer and a Q phase on a second layer, which are integrated into an associated processor chip for required quadrature signal generation according to one or more embodiments shown and described herein;

[0018] Figure 5B Schematically depicts a device positioned within a reservoir according to one or more embodiments shown and described herein. Figure 5A A variable capacitor of a capacitive voltage divider;

[0019] Figure 6 is a cross-sectional view of an interdigitated electrode capacitor formed with electric field lines to prevent oil in which an associated processor is immersed from adhering between the thickness of the capacitor plates, thereby increasing sensing speed and improving associated response time, in accordance with one or more embodiments shown and described herein;

[0020] Fig. 7A is a circuit diagram of an unbalanced capacitor pair accompanied by a balanced voltage pair of anti-phase voltage sources according to one or more embodiments shown and described herein;

[0021] Figure 7B is a circuit diagram of a balanced capacitor pair with a single control capacitor inserted, and a balanced voltage pair with anti-phase voltage sources, according to one or more embodiments shown and described herein;

[0022] Figure 7C is a circuit diagram of a balanced capacitor pair with two control capacitors inserted, and a balanced voltage pair with anti-phase voltage sources, according to one or more embodiments shown and described herein;

[0023] Figure 8 illustrates a sensor layout having a diamond design according to one or more embodiments shown and described herein;

[0024] Fig. 9 illustrates diamond design parameters according to one or more embodiments shown and described herein;

[0025] Fig.10 illustrates a connector pinout on a sensor according to one or more embodiments shown and described herein;

[0026] Fig.11illustrates a circuit layout on a PCB according to one or more embodiments shown and described herein;

[0027] Fig.12 Schematically illustrates an LC inductive sensor with a differential LC oscillator and a Thevenin equivalent circuit according to one or more embodiments shown and described herein;

[0028] Fig.13 schematically illustrates a current steering bridge circuit having a differential amplifier with a current sink to form a bridge circuit according to one or more embodiments shown and described herein;

[0029] Fig.14A Schematically illustrates a device according to one or more embodiments shown and described herein. Fig.13 A pilot bridge circuit in which the impedance is replaced by a bridging impedance element;

[0030] Fig. 14B schematically illustrates an embodiment according to one or more embodiments shown and described herein, Fig.14A Thevenin equivalent current steering bridge circuit;

[0031] Fig.15A Schematically illustrates a device having a Fig.14A A quarter bridge differential impedance current steering bridge circuit;

[0032] Fig. 15B Schematically illustrates a device having a Fig.14A A quarter bridge differential impedance current steering bridge circuit;

[0033] Fig.16 Schematically illustrates a device having a Fig.14A A differential capacitor current steering bridge circuit of a quarter bridge;

[0034] Fig.17A schematically illustrates a center-tapped differential inductive current steering bridge circuit with two variable inductors according to one or more embodiments shown and described herein;

[0035] Fig. 17B schematically illustrates a center-tapped differential inductive current steering bridge circuit with four variable inductors according to one or more embodiments shown and described herein;

[0036] Fig. 17Cschematically illustrates a single bridge differential circuit according to one or more embodiments shown and described herein;

[0037] Fig.17D schematically illustrates a differential bridge circuit having a dual bridge according to one or more embodiments shown and described herein;

[0038] Fig.17E schematically illustrates a single-bridge ratiometric circuit according to one or more embodiments shown and described herein; and

[0039] Fig.18 Schematically illustrates a ratiometric output of a differential capacitive current steering bridge circuit according to one or more implementations shown and described herein. DETAILED DESCRIPTION

[0040] Embodiments described herein relate to a system having a processor and a bridge circuit. The bridge circuit includes a pair of differential voltage sources, a first pair of sensing elements, and a second pair of sensing elements. The pair of differential voltage sources is configured to drive the first bridge circuit.

[0041] The first pair of sensing elements and the second pair of sensing elements may each be configured to generate a pair of measurement signals. The pair of measurement signals are independent of each other and are based on the corresponding sensing elements. The second pair of sensing elements are communicatively coupled to the first pair of sensing elements. The second pair of sensing elements defines a first divider. The first divider is configured to output a first output signal to the processor. The first output signal is a differential signal.

[0042] As will be further described below, the first pair of sensing elements and the second pair of sensing elements are a combination from a group of capacitors, inductors and resistors. In an embodiment in which the first pair of sensing elements generates a pair of measurement signals, the pair of measurement signals are input into the corresponding second sensing elements in the second pair of sensing elements. The pair of measurement signals is a differential measurement corresponding to the force in contact with the bridge circuit. The differential measurement can be impedance, inductance or capacitance, or a combination thereof.

[0043] In an embodiment where the second pair of sensing elements generates a pair of measurement signals, the pair of measurement signals are independent of each other and are based on the respective second sensing elements. In this embodiment, the pair of measurement signals are a differential measurement corresponding to the force of contact with the bridge circuit. The differential measurement can be impedance, inductance or capacitance, or a combination thereof.

[0044] In some embodiments, the bridge circuit is a single bridge for differential output. In other embodiments, the bridge circuit is a dual bridge for ratiometric output. Therefore, in a dual bridge embodiment, the bridge circuit may include a third pair of sensing elements, which are communicatively coupled to the first pair of sensing elements and connected in parallel with the second pair of sensing elements. The third pair of sensing elements is a combination from a group of capacitors, inductors and resistors. The third pair of sensing elements can receive or generate a second pair of measurement signals, which are received or generated by a corresponding third sensing element in the third pair of sensing elements, corresponding to the force in contact with the bridge circuit. The third pair of sensing elements defines a second divider. The third pair of sensing elements outputs a second output signal to the divider. The divider divides the first output signal by the second output signal to generate a ratiometric signal.

[0045] It should be understood that by using a bridge circuit, the differential signal and / or ratiometric signal is independent of common mode noise from the transducer and circuit. Therefore, independent differential signals can be used, or ratiometric measurements of differential outputs can be used simultaneously.

[0046] That is, as will be further described, the bridge circuit is configured for differential measurements for maximum information transfer, while non-differential measurements include specific signals and common signals that are not part of the information. In addition, ratiometric measurements for different media are measured using the same sensor configuration because all common mode signals are rejected. The bridge circuit with ratiometric measurements allows the implementation of not only capacitive sensors, but also inductive sensors and resistive sensing within the sensing architecture.

[0047] As used herein, the term "communicatively coupled" means that the coupled components are able to exchange data signals and / or electrical signals with each other, such as, for example, electrical signals via a conductive medium, electromagnetic signals via air, optical signals via optical waveguides, electrical energy via a conductive medium or a non-conductive medium, wirelessly and / or data signals via a conductive medium or a non-conductive medium, etc.

[0048] In summary, and with reference to the accompanying drawings, Figure 1A A circuit diagram of a pair of anti-phase voltage sources supplying an LC circuit and ultimately a processor chip is generally shown at 10, which is subsequently referenced by the general example at 74 and in one variation includes an inductive sensor chip and is known to provide superior robustness and longevity compared to magnetic sensors when applied to a wide range of vehicle applications including linear / rotary pedal position, fuel level, etc. Although not shown, existing current inductive sensors may also include a miniaturized processor chip or PC board having signal processing components disposed thereon with an inductive signal input function, such as including an aluminum rotor supported on a transmitting coil and receiving coil arrangement.

[0049] In accordance with the teachings of the present invention, a pair of variable capacitors associated with the chip may also include spatial array plates immersed in a fluid (eg, oil) medium to provide a fluid level reading. Figure 1A The circuit 10 in FIG. 1 also depicts a pair of anti-phase excitation voltage sources at 12 and 14 located on opposite sides of a capacitor 16 associated with an LC resonator of the inductive sensor drive circuit, see 18 , the output of which is supplied as a minute current (typically less than 1 mA) through an ammeter 20 for subsequent conversion into a varying voltage output.

[0050] Figure 1B is a diagram of a current steering bridge circuit with a bias voltage (see generally at 22), wherein a pair of sensor capacitors (see variable capacitor Csen at 24 and capacitor CREF at 26) are connected to anti-phase voltage sources 12 and 14, whose amplitudes are the same for all drive frequencies (e.g., including a non-limiting range from hundreds of Khz to tens of Mhz). In such an arrangement, variable capacitor 24 becomes a current source, pumping a certain amount of excitation current (see at 28) through resistor 30, while another capacitor 26 generates excitation current 32 through resistor 34.

[0051] The current steering bridge circuit structure operates to steer anti-phase currents generated between the capacitors in differential amounts, with the resulting sense current (see 36 and corresponding to the differential current) appearing as a voltage 38 across resistor 36 . Figure 1C Provides sources such as Figure 1B 4 is a diagram of a pair of sine signals 40 and cosine signals 42 of a pair of current steering bridge circuits for use with a signal processor chip also suitable for inductive sensor applications.

[0052] Figure 2 Picture shows Figure 1B As further generally shown at 44, see 38', the source voltage being set equal to zero indicates that the output voltage is proportional to the differential capacitance 36' when the reading is approximately zero.

[0053] Figure 3 A system 500 is schematically depicted, comprising a transducer 502 having three terminals 504a, 504b, 504c, which are communicatively coupled to an inverting voltage source 58, 60. The inverting voltage source 58, 60 is configured to drive a first variable capacitor 505 and a second variable capacitor 507 to produce a level output 406 and a reference output 508. It should be understood that the application is not limited to capacitors, and may be an inductor, a resistor, and / or a combination thereof. Thus, Figure 3A linear ratiometric output 510 is illustrated with a three-terminal transducer. It will be appreciated that such an arrangement allows for a compact transducer board. The linear ratiometric output 510 is described with respect to a graph 512 having an ordinate 514 and an abscissa 516, wherein the level output 506 and the reference output 508 may be graphically illustrated as a level output graph 518 and a reference output graph 520. Graph 512 also illustrates a liquid level 522, a bottom 526, and a zero liquid point 524. The bottom 526 may be the bottom of a reservoir or the like.

[0054] The zero liquid point 524 can be the lowest liquid level required to obtain a reading. As shown, the linear ratiometric output 510 is independent of the liquid level 522. Therefore, by taking the ratio of the two differential outputs (e.g., level output 506 and reference output 508) that change with the liquid level 522, the ratiometric output 510 is independent of the fluid, and the bridge circuit eliminates common mode noise from the transducer and circuit, as discussed in more detail herein. It should be understood that the liquid level 522 is only for exemplary purposes, and can also be described with pressure, force, etc., so that there are two differential outputs. For example, in the case of force, one level output is the force measured when the force is applied, and the reference output is the normal force when no force is applied.

[0055] Figure 4 A system 530 is schematically depicted, which includes a transducer 532 having four terminals 534a, 534b, 534c, 534d that are communicatively coupled to an inverting voltage source 58, 60. The inverting voltage source 58, 60 is configured to drive a first variable capacitor 535 and a second variable capacitor 537 to produce a sine output 536 and a cosine output 538. It should be understood that the application is not limited to capacitors, and may be an inductor, a resistor, and / or a combination thereof. Thus, Figure 4 The quadrature ratio metric output 540 accompanying the four-terminal transducer is illustrated. It should be understood that such an arrangement allows for a compact transducer board and may require an inverse tangent processor. The quadrature ratio metric output 540 is described with respect to a chart 542 having an ordinate 544 and an abscissa 546, wherein the sine output 536 and the cosine output 538 may be graphically illustrated as a sine output graph 548 and a cosine output graph 550. The chart 542 also illustrates a liquid level 552, a bottom 554, and a zero liquid point 556. The bottom 554 may be the bottom of a reservoir or the like.

[0056] The zero liquid point 556 can be the lowest liquid level required to obtain a reading. As shown, the orthogonal ratio measurement output 540 is an angle output that is independent of the liquid level 552. Therefore, by taking the angle ratio of the two differential outputs (e.g., sine output 536 and cosine output 538) that change with the liquid level, the orthogonal ratio measurement output 540 is independent of the fluid, and the bridge circuit eliminates common mode noise from the transducer and circuit, as discussed in more detail herein. It should be understood that the liquid level 522 is only for exemplary purposes, and can also be described in terms of pressure, force, etc., so that there are two differential outputs. For example, in the case of force, one level output is the force measured when the force is applied, and the reference output is the normal force when no force is applied.

[0057] Figure 5A and Figure 5B Accordingly, a schematic diagram of a system 49 having a capacitive plate is provided. The plate is a first variable capacitor 50 and a second variable capacitor 52 implemented within a multilayer printed circuit board (PCB) 54. The PCB 54 may have a first layer 55a and a second layer 55b, wherein the first layer may be the I phase and the second layer may be the Q phase. The system 49 also includes an anti-phase voltage source 58, 60 configured to drive the first variable capacitor 50, and the second variable capacitor 52 corresponds to a quadrature signal generated by the pair of anti-phase voltage sources, wherein the detected signal represents a differential value of the voltage.

[0058] Variable capacitor 50,52, PCB 54 and / or inverting voltage source 58,60 can be integrated into a processor 74 configured for orthogonal signal generation.It should be understood that the differential capacitance of each signal can be set to about 5pF (picofarad) or greater.It should be understood that the differential capacitance of each signal can be set to less than 5pF (picofarad).It is further understood that the depicted layout represents only a possible example of a capacitor plate structure.In one embodiment, the capacitor plate structure can include a simple strip provided for each electrode to minimize the in-plane capacitance compared to the out-of-plane capacitance.

[0059] In various embodiments, the variable capacitors 50, 52 may be configured to detect a rise in level 56a in an area having a pair of sidewalls 62, a change in force 56b between the sidewalls 62 caused by movement of the sidewalls, a change in a fluid, gas, etc. caused by force and / or some other method, etc. For example, the area may be a reservoir, a pair of plates, etc., so that the area may be any area in which a fluid, pressure, force, etc. may be measured. For example, it is contemplated that a force is applied to a pedal pad of a brake, accelerator, or clutch pedal. That is, a change in force between plates, etc., acting on a bridge circuit may be used by a fluid, gas, solid, or other agent, so that the bridge circuit senses such a change and may be compared to a reference bridge circuit to determine the amount of force, so that a reference capacitor may be used to determine creep and other principles. It should be understood that the arrows 56a, 56b are merely illustrative and that the direction of the force or rise in level may be in any direction between the pair of sidewalls 62. In addition, it should be understood that at least one of the variable capacitors may be connected in series with another passive element 64 to form a divider having an output 66. The passive components may be capacitors, resistors, inductors, and / or combinations thereof.

[0060] Figure 6 80 is a cross-sectional view of the interdigital electrode capacitance formed by the array of electric field lines (see in-field 82 and out-field 84) between the ground fingers 86 and the AC capacitor fingers 88, which helps prevent the oil in which the associated processor is immersed from adhering between the thickness of the capacitor plates, thereby increasing the sensing speed and improving the associated response time. The main viscous force causes the gap to form, and the in-field lines 82 exist at a relatively high density. It should also be understood that when the narrow gap is filled with an epoxy resin such as a coating, this area will not respond to the interaction of the oil, which further helps to reduce signal errors.

[0061] As further supported by the above description, a feedback loop with an LC circuit is applied to the received voltage 12, 14 to maintain a constant value to compensate for aging / acidification changes in the dielectric constant associated with the target fluid (e.g., oil), it being understood that the difficulty in fluid capacitance measurement is largely due to changes in the dielectric constant of the fluid due to aging / acidification of the fluid. The feedback loop on the received voltage maintains a constant value based on a predetermined function, wherein the excitation voltage 12, 14 is varied to maintain one or more input signals constant.

[0062] Additional changes in the correction feedback loop may include employing a sampling mechanism that exhibits a higher resolution than required to allow the input signal to be reduced while still maintaining output resolution as the excitation voltage reaches its limits. In one non-limiting example, such control may provide a dielectric constant greater than a factor or four times the range (4x) with a given fluid type.

[0063] In fluid applications, it is important to balance the RF capacitor sensor with respect to the dielectric constant. The balance of the capacitor will define the zero signal point, allowing the level to be measured regardless of the dielectric constant of the fluid. This is important for obvious reasons, such as changes in the dielectric constant due to temperature, thickness, breakdown, etc. of the fluid. A balanced capacitor pair needs to be matched to the output capacitance (Q OUT ) the same amount of input capacitance (Q IN ).

[0064] like Fig. 7A The unbalanced circuit shown in circuit 100 in FIG. 1 illustrates that due to the geometric configuration of the control relay and the capacitor plates, the voltage V sen 122 is greater than zero. Fig. 7A The circuit 100 in FIG. 1 also depicts a resistor 103 and a pair of anti-phase voltage sources (in-phase voltage 102 and out-of-phase voltage 104), whereby the anti-phase voltage sources 102 and 104 generate a balanced voltage pair 106, where V IN =-V OUT Further depicted is a pair of capacitors C connected to the inverting voltage sources 102 and 104. IN 108 and C OUT 110, and an additional control capacitor C crtl1 114, which is connected to the capacitor C IN 108 are connected in parallel and driven by the common-mode voltage source 102 connected at 117, so that V sen 122 is an unbalanced capacitor pair 112 that is greater than zero.

[0065] See 120 in total, Figure 7B is a depiction of the balanced capacitor system 124, where V sen 122 equals zero. Figure 7B The circuit 120 in FIG. 1 also depicts a resistor 103 and inverting voltage sources 102 and 104, which thus produce a balanced voltage pair 106. Further depicted is a balanced system 124 having a pair of capacitors C connected to the inverting voltage sources 102 and 104. IN 108 and C OUT 110, and an additional control capacitor C crtl1 114, the additional control capacitor C crtl1 114 and capacitor C IN 108 are connected in parallel, but driven by the inverting voltage source 104 at the connection point 118. This allows the unbalanced capacitor pair to be balanced by the voltage pair. In other words, the control capacitance driven by the opposite branch is equal to the unbalanced part of the capacitor pair. This can be described by the following equation:

[0066] Equation 1: C IN V IN +C ctrl1 V OUT =C OUT V OUT

[0067] Equation 2: (C IN -C ctrl1 )V IN =C OUT V OUT

[0068] A control capacitor may be added to circuit 120 to balance the capacitors using the above equation, where C IN Greater than C OUT The same principle applies by adding a control capacitor and wiring the control capacitor to the opposite branch of the voltage pair, V sen is equal to 0.

[0069] However, by adding a single control capacitor, a parasitic imbalance may occur. To offset any parasitic losses or stray capacitance, a second control capacitor may be added with any voltage pair. Figure 7C The circuit 130 is shown with an additional control capacitor C crtl2 116, the additional control capacitor C crtl2 116 was added to match C IN 108 are connected in parallel and similarly connected to the in-phase voltage 102 at the connection point 132. Balancing by inserting the control capacitor can be described by the following equation:

[0070] Equation 3: C IN V IN +C ctrl1 V OUT =C OUT V OUT +C ctrl2 V IN

[0071] By definition, using V OUT =-V IN , Equation 3 becomes:

[0072] Equation 4: (C IN V IN -C ctrl1 )V IN =(C OUT V OUT -C ctrl2 )V OUT

[0073] It should be understood that C crtl2May be added to any unbalanced capacitance, such as parasitic capacitance of wiring and connectors.

[0074] like Figure 8 As depicted in FIG. 1 , a diamond-shaped layout 148 of drivers and driver wires is shown (shown as a long and short line pattern). In addition, Figure 8 A quadrature signal balancing arrangement is depicted, having a signal driver 150 and a signal driver 152, wherein the signal drivers 150 and 152 drive the cosine and sine signals through the capacitor pair driven by the voltage pair 102, 104, respectively. It should be understood that other signal balances and other drivers may be used. In addition, in such a final assembly of the sensor 146, tuning pads 154, 156 may be necessary in order to balance the final system. The balancing mechanism may be achieved by the same balancing mechanism discussed herein, i.e., using sliding tuning capacitors 154, 156 wired to opposite phases of the voltage pair 102, 104. In addition, the overlap or distance between the tuning pads forms the capacitance required to balance the system, such as the distance X corresponding to the distance between the tuning pads 154, 156 and the voltage connection 166, 168. crtl 162 and Y crtl In particular, the in-phase voltage source 102 is operably connected to a voltage connection point 168 via a conductor 160 and is located a distance Y from the tuning pad 156. crtl Similarly, the out-of-phase power supply 104 is operatively connected to the voltage connection point 166 via the conductor 158 and is located at a distance X from the tuning pad 154. crtl .

[0075] Fig. 9 It is depicted that under diamond balanced cancellation of the wires, the distance between the two power lines or voltage sources 102, 104 should be closer than the distance between the signal lines 154, 156. It should be understood that the coupling between the signal and any phased power line is the same as long as a diamond can be drawn on the connecting wire as shown. When a diamond can be formed, if the distance ΔY 172 ≥ ΔX 170, the wire cancellation is automatically met; however, the distance ΔY 172 between the signals 156, 154 should be as large as possible within the design limits. It should be understood that such a diamond design for any connector wire assembly works to cancel the wires, whether it is an IDF or orthogonal sensor type. In addition, the diamond diagram may be combined with the sensor PCB and the connecting wire assembly to eliminate electrical effects.

[0076] Now return to reference Figure 8, parasitic losses of a balanced system may produce unexpected capacitance. Therefore, parasitic losses can be controlled by using tuning pads 154, 156 located at each signal driver 150, 152 respectively and a diamond diagram 148 (indicated by dotted lines) for the connector wire assembly. Calibration of the system can be used wherever there is a capacitive imbalance. In addition, sensor board imbalance can also be tuned in this method. In addition, connector pins and circuit imbalance can be tuned in the same way.

[0077] Fig.10 The layout of the connector pins on the sensor is depicted. As shown, a diamond pin pattern 148 is met to connect the wires between the sensor 146 and the circuit 176, thereby ensuring signal decoupling. As shown, the distance between the two power lines 102, 104 is as close as possible 180, 182, while the distance between the two signal lines 154, 156 is as large as possible 178, 184. In addition, although the pin layout is illustrated vertically, it can be any configuration in which the signal line is separated by at least two power lines.

[0078] Fig.11 The sensor's tuning pad and drive pin layout are depicted. The diamond design 148 is clearly visible in the sensor layout 146. Again, as shown, the distance between the two power lines 102, 104 is as close as possible, while the distance between the two signal lines 154, 156 is as large as possible. In addition, the signal line crosses the power line at right angles.

[0079] Fig.12 Schematically illustrates an LC inductive sensor with a differential LC oscillator and a Thevenin equivalent circuit. The LC inductive sensor 200 includes a pair of N-channel transistors 204 having a bridge element 208 between drains 206. The LC inductive sensor 200 also includes a voltage divider 210 having a pair of passive components 212 providing a single differential output 214. Therefore, it should be understood that the LC inductive sensor 200 is a single AC bridge for a single differential output 214. In addition, the LC inductive sensor 200 includes a pair of capacitors 216, wherein each capacitor is connected in parallel and connected to one inductor and one resistor in a pair of inductors 218 and resistors 220, wherein each inductor 218 and resistor 220 in the pair is connected in series with each other and with the capacitor 216. The tail current 222 is absorbed by the pair of transistors 204 and by the corresponding drain load 206.

[0080] As shown, the Thevenin equivalent 202 is taken from a pair of inductors 218, so the equivalent source impedance 224a is R s1=Q[ω(L+Δ)+R], and the equivalent source impedance 224b is R s2 =Q[ω(L-Δ)+R] In addition, an equivalent differential voltage source V having source impedance and complementary output strength can be calculated through a single differential output 214. m 226 and reverse voltage source V' m 228. The Thevenin equivalent 202 transforms the source impedances 224a, 224b by a factor of Q. Thus, the circuit acts as an impedance amplifier, multiplying the amount of inductance Δ in the inductance sensing circuit. The single differential output 214 of the inductance sensing is It should be understood that any impedance element of circuit 200 and equivalent circuit 202 can be amplified by Q times, and the LC oscillator can be used as a sensor with a differential signal. It should be understood that the factors Q and I phase have opposite direction currents. In addition, it should be understood that any small change in the resistor, capacitor or inductor will be amplified by twice the tail current.

[0081] Fig.13 A current steering bridge circuit 230a is schematically illustrated having a differential amplifier with a current sink to form a bridge circuit. Tail currents 232, 234 are sunk with a pair of transistors 236, 238 having corresponding drain loads 240, 242. The bridge element between the drains 240, 242 of the transistors 236, 238 allows for a differential current between the loads of the drains 240, 242. Since the drains 240, 242 are loaded between the transistors 236, 238, the drain loads are balanced without any current passing through the bridge element. However, if there is an impedance that creates an unbalanced condition on the drain load, and if the transistors 236, 238 are turned on, there will be current flowing through the bridge, which can be sensed.

[0082] Therefore, by leaving one drain load unchanged and replacing the other drain load with a sensing element having an impedance that is residually matched to the drain load, such as but not limited to a capacitive, inductive, or electrical sensing element configured to detect a change in resistance of a semiconductor or metal under mechanical strain, the guiding bridge 230 becomes a sensing circuit.

[0083] The guiding bridge 230a includes a pair of bridging impedance elements Z br 247 of the voltage divider 246, the impedance element Z br 247 has an output V out 248. In addition, the guide bridge 230 includes an impedance Z+Δ 250 and Z-Δ 252. Impedances 250, 252 may be replaced by a bridge impedance element 247 to become a bridge impedance element within the voltage divider 246.

[0084] Fig.14AThe following diagram schematically illustrates the additional circuitry after the impedances 250 and 252 are replaced by the bridging impedance element 247. Fig.13 The voltage inputs 237 and 239 on transistors 236 and 238 are connected to the current sources 232 and 234 and the load impedance element Z br 247 is complementary. Therefore, the steering bridge circuit 230b has a similar Thevenin equivalent, as described above Fig.12 However, in the current steering bridge circuit 230b, due to the voltage divider 246 ( Fig.13 ) and the bridge impedance element 247 with a strong impedance (1 / gm), the voltage output 248 is significantly weaker. Therefore, in sensor applications, the output voltage 248 is differential and proportional to the difference Δ.

[0085] Fig. 14B Schematically illustrates Fig.14A Thevenin equivalent current steering bridge circuit. In the Thevenin equivalent circuit 230c, the circuit component 254a ( Fig.14A ) of transistor 236 ( Fig.14A )、Current 232( Fig.14A ) and impedance 247( Fig.14A ) can be combined into a voltage source V m 264 and source impedance Z s 260. Similarly, circuit component 254b ( Fig.14A ) of transistor 238 ( Fig.14A )、Current 234( Fig.14A ) and impedance 247( Fig.14A ) can be combined into a voltage source V' m 266 and source impedance Z s Therefore, the voltage sources 264, 266 are strong enough so that the source impedances 260, 262 become smaller than the bridge impedances 250, 252, so that the output voltage 248 can be obtained by the equation Determine where the source V m 264 and source V' m 266 is the differential amplitude pair of the voltage source.

[0086] Fig.15A Schematically illustrates Fig.14A The current steering bridge circuit 230d with a quarter bridge includes a differential voltage source 270, which includes a voltage source V m 264 and voltage source V' m 266. The differential AC voltage source 270 has a frequency of 4 MHz and an amplitude of V mIt should be understood that the frequency of the differential voltage source can be greater or less than 4 MHz. The sign convention on the voltage sources 264, 266 indicates the phase of the AC voltage. Source impedance Z s 260, 262 are connected to a voltage source V m 264 and voltage source V' m 266. The differential voltage source 270 drives the bridge, which includes Z ref +Δ272 and Z ref 274. The impedance pair 272, 274 is a pair of capacitors, but is not limited to capacitors, and as discussed below, can be inductors, resistors, and / or other elements. The voltage divider 276 is connected to the bridge at node 'a' 286 and includes an impedance pair Z1 278 and Z2 280. It should be understood that the impedance pair 278, 280 can be a pair of capacitors, inductors, resistors, any combination thereof, and / or other elements.

[0087] The difference of the differential impedance detection impedance pair is Δ=(Z ref+Δ -Z ref ). When Δ and source impedance Z s When 260 and 262 are small, the output 282 at the bridge node 'a' 286 becomes In addition, the frequency of the output voltage 282 of the bridge at node 'a' 286 is too high and is generally a delayed signal (phase lag) that must be attenuated and requires phase adjustment. As a result, the voltage divider 276 of the current steering bridge 230c acts as a passive network to attenuate and adjust the phase. It should be understood that the current steering bridge circuit 230d can be applied to various sensing elements that decode differential signals, including capacitive, inductive or resistive sensing elements. The output 284 of the voltage divider 276 at node 'b' 288 is directed to a signal processor 290 configured for an LC oscillator. Therefore, the current steering bridge circuit 230d is a single AC bridge that provides a differential signal output 284.

[0088] Fig. 15B Schematically illustrates Fig.14A The current steering bridge circuit 230e includes a differential impedance current steering bridge circuit with a frequency of 4 MHz and an amplitude of V m The differential AC voltage source 270 is a differential AC voltage source. It should be understood that the frequency of the differential voltage source can be greater than or less than 4 MHz. The differential voltage source 270 includes a voltage source V m 264 and voltage source V' m 266. The sign convention on the voltage sources 264, 266 indicates the phase of the AC voltage.

[0089] The differential voltage source 270 drives a bridge comprising a pair of sensing coils L ref +Δ292 and Lref 294. Coil pair 272, 274 is a pair of inductors, but is not limited to inductors and, as previously discussed, may be capacitors, resistors, and / or other components. Coupler 296 is positioned relative to sensing coil pair 272, 274 so that coupler 296 can move along sensing coil pair 272, 274 such that the position of the coupler is detected by the differential signal generated by current steering bridge output 282 at bridge node 'a' 286, where The voltage divider 276 is connected to the bridge at node 'a' 286 and includes an impedance pair Z1 278 and Z2 280. It should be understood that the impedance pair 278, 280 may be a pair of capacitors, inductors, resistors, any combination thereof, and / or other components. The voltage divider 276 provides a signal processor 290 ( Fig.15A ) with the appropriate attenuation and phase required. Thus, the current steering bridge circuit 230e is a single AC bridge that provides a differential signal output 284.

[0090] Fig.16 Schematically illustrates Figure 14A-14B , Figure 15A-15B The current steering bridge circuit 230f is shown as having a differential AC voltage source 270 having a voltage source V m 264 and voltage source V' m 266. The sign convention on the voltage sources 264, 266 indicates the phase of the AC voltage. The differential voltage source 270 drives the bridge, which is shown as having a capacitor pair C ref +Δ300 and C ref 302. It should be understood that while the differential capacitive current steering bridge circuit 230f is illustrated as having a capacitor pair, this is non-limiting and may be replaced with an impedance pair, a resistor pair, and / or a combination of capacitors, inductors, and resistors. The voltage divider 276 is connected to the bridge at node 'a' 286 and includes an impedance pair illustrated as a capacitor Z1 278 and a second impedance Z2 280. It should be understood that the impedance pair 278, 280 may be a pair of capacitors, inductors, resistors, any combination thereof, and / or other elements.

[0091] Capacitor C ref +Δ300 can be printed on PCB 54 ( Figure 5B ) and may be in contact with a measurable medium 304, such as a gas, pressure, fluid, etc. that may change or vary based on force, liquid level, etc. In some embodiments, a force may be applied to a capacitor C ref+Δ300 measured fluid, gas, pressure, etc. In other embodiments, as discussed in more detail herein, the force may be applied directly to a pair of plates, side walls, etc., which may be connected to capacitor C ref +Δ300 is detected or the space between them can be made by capacitor C ref In addition, it should be understood that the force applied to the fluid, gas, the pressure, the change in space, etc. can be in C ref +Δ300 as a reference and at multiple angles (0 degrees to 360 degrees) as illustrated by directional arrows 306. As the measurable medium 304 changes in any direction, as indicated by directional arrows 306, the measurable medium 304 changes so that the change in the measurable medium 304 is at least ref +Δ 300 is detected and outputted by differential signal output 282, which is due to the change in capacitance Δ as the measurable medium 304 in contact with capacitor 300 changes. Voltage divider 276 provides signal processor 290 ( Fig.15A ) with the appropriate attenuation and phase required. Thus, the current steering bridge circuit 230f is a single AC bridge that provides a differential signal output 284.

[0092] It should be understood that discrete components can be used to replace capacitor C ref +Δ300, and the pilot bridge circuit 230f can behave in the same manner by using the amount or level of the measurable medium 304 moving along the sensing electrode pair, since the change Δ varies with the amount or level of the measurable medium 304.

[0093] It should be understood that due to the differential AC voltage source 270 ( FIG. 14A to FIG. 16 ) operates at 4 MHz, so the advantage over conventional capacitive sensor designs is that this embodiment operates at a frequency nearly 400 times higher than conventional capacitive sensors. Therefore, the source impedance becomes 400 times lower than conventional capacitive sensors, resulting in much better noise performance for the capacitive sensor of this embodiment.

[0094] It should be understood that the above embodiments are not limited to the differential voltage source as described above. In a non-limiting example, the LC oscillator circuit with a center tap can be transformed into a circuit with a transformed series resistance R and a phase quantity V m The equivalent source impedance R s becomes the Q of the original circuit multiplied by R, and V can be estimated from Q and the tank impedance m .

[0095] Furthermore, if the inductor does not have a center tap for supplying power, but instead has a pair of identical resistors supplying power to the circuit, the circuit functionality will be almost the same as the circuit with a center tapped inductor, however there will be a lower voltage swing due to the loss of the Q quality factor of the supply resistor pair. Such a differential voltage source structure is advantageous in that it provides for the differential voltage pair V to be fine-tuned using the supply resistor pair. m and V' m The proper balance of the voltage source can be easily calibrated, which is inherently easier than using an inductor. In addition, such a voltage source configuration is advantageous because in some applications, V out The average voltage is used to eliminate the bias voltage downstream of the circuit so that when the sensing element is a conductive element.

[0096] Fig.17A A dual-bridge differential inductive current steering bridge circuit with two variable inductors without a center tap is schematically illustrated. The current steering bridge circuit 310 includes a pair of resistors 312, 314, a capacitor 324, a tail current 330, and two bridges 315, 319. Although illustrated as a pair of resistors 312, 314 and a capacitor 324, this is non-limiting, and the pair of resistors 312, 314 can be a pair of inductors, a pair of capacitors, and / or a combination thereof. The capacitor 324 can be a resistor and / or an inductor. The first bridge 315 having a node 317 separates a first pair of sensing elements including a first sensing element 316 and a second sensing element 318, wherein the first sensing element 316 has an incremental change. That is, the first sensing element 316 is configured to detect a change in a quantity in the measurable medium 304, such as may be caused by a change in liquid level, a force direction 306 ( Fig.16 ) caused by the force on the fluid, pressure, gas, etc. As discussed in more detail herein, the second sensing element 318 is configured to detect the reference measurable medium 304a ( Fig.16 ) reference value 306a. The first sensing element and the second sensing element 316, 318 can be a pair of inductors, a pair of capacitors, a pair of resistors and / or a combination thereof. It should be understood that the device configured to detect the measurable medium 304 ( Fig.16 ) is non-limiting, and the second sensing element 318 may be configured to detect a change in the amount of the measurable medium 304 ( Fig.16 ), and the first sensing element 316 can be configured to detect the change in the amount of the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ). The first bridge 315 outputs a first differential signal 326 from the node 317. The first differential signal 326 may include a signal corresponding to the measurable medium 304 ( Fig.16) and information related to the difference between the reference measurable medium 304a sensed by the second sensing element 318.

[0097] The second bridge 319 has a second node 321 that separates a second pair of sensing elements including a third sensing element 320 and a fourth sensing element 322, wherein the fourth sensing element 322 has an incremental change. That is, the fourth sensing element 322 is configured to detect the measurable medium 304 ( Fig.16 ) in the quantity, such as may be caused by changes in liquid level, force direction 306 ( Fig.16 ) caused by the force on the fluid, pressure, gas, etc., as discussed in more detail herein. The third sensing element 320 is configured to detect the measurable medium 304a ( Fig.16 ) reference value 306a, as discussed in more detail herein. The third and fourth sensing elements 320, 322 may be a pair of inductors, a pair of capacitors, a pair of resistors, and / or combinations thereof. It should be understood that the device configured to detect the measurable medium 304 ( Fig.16 ) is non-limiting, and the third sensing element 320 may be configured to detect a change in the amount of force direction 306 or other changes in the fourth sensing element 322 of the measurable medium 304 ( Fig.16 ) in the amount of force or other changes, and the fourth sensing element 322 can be configured to detect the measurable medium 304 ( Fig.16 ) of the reference value 306a( Fig.16 ). The second bridge 319 outputs a second differential signal 328 from the second node 321. The second differential signal 328 may include the measurable medium 304 ( Fig.16 ) and the reference measurable medium 304a sensed by the third sensing element 320 ( Fig.16 ) related to the differences sensed between the two.

[0098] In addition, in some embodiments, the first differential signal 326 and the second differential signal 328 are input to the divider 329, thereby dividing the signal or converting it into a ratio indicated by the ratio metric output 329a. It should be understood that the bridge circuit 310 can be an LC circuit without a center tap and includes more than one set of sensing coils. Since the inductance of the resonator has a dual function, the sensing coils can be separated. First, as a resonator coil, and then, when the anti-eddy current plate is modulated, as a sensing coil. That is, the first differential output 326 can be output from the first bridge 315 between a pair of sensing elements 316, 318, and the second differential signal 328 can be generated from the second bridge 319 between two separate and different sensing elements 320, 322. Therefore, it is possible to use an LC oscillator circuit 310 in a position such as a container, a tank, a compressible pair of side walls or plates, etc., or between more than one or a separate container, a tank, a compressible second pair of side walls or plates, etc.

[0099] Fig. 17B A differential bridge circuit 332 with four variable inductors without a center tap is schematically illustrated. The bridge circuit 332 includes a pair of resistors 334, 336, a capacitor 350, a tail current 352, and two bridges 335, 339. Although illustrated as a pair of resistors 312, 314 and a capacitor 350, this is non-limiting, and the pair of resistors 312, 314 can be a pair of inductors, a pair of capacitors, and / or a combination thereof. The capacitor 350 can be a resistor and / or an inductor. The first bridge 335 has a node 337 that separates a first pair of sensing elements including a first sensing element 338 and a second sensing element 340, wherein both the first sensing element 338 and the second sensing element 340 are variable, and the first sensing element 338 has an incremental change. The first sensing element and the second sensing element 338, 340 can be a pair of inductors, a pair of capacitors, a pair of resistors, and / or a combination thereof.

[0100] That is, the first sensing element 338 is configured to detect the measurable medium 304 ( Fig.16 ) in the quantity, such as may be caused by changes in liquid level, force direction 306 ( Fig.16 ) caused by the force on the fluid, pressure, force, gas, etc. The second sensing element 340 is configured to detect the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ), as discussed in more detail herein. It should be understood that the device configured to detect the measurable medium 304 ( Fig.16 ) is non-limiting, and the second sensing element 340 may be configured to detect a change in the amount of the measurable medium 304 ( Fig.16), and the first sensing element 338 can be configured to detect the change in the amount of the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ). The first bridge 335 outputs a first differential signal 346 from the first node 337. The first differential signal 346 may include a signal corresponding to the measurable medium 304 ( Fig.16 ) and the reference measurable medium 304a sensed by the second sensing element 340 ( Fig.16 ) related to the differences sensed between the two.

[0101] The second bridge 339 has a second node 343 that separates a second pair of sensing elements including a third sensing element 342 and a fourth sensing element 344, wherein the third sensing element 342 and the fourth sensing element 344 are both variable and the fourth sensing element 344 has an incremental change. The third sensing element and the fourth sensing element 342, 344 can be a pair of inductors, a pair of capacitors, a pair of resistors, and / or a combination thereof. That is, the fourth sensing element 344 is configured to detect the measurable medium 304 ( Fig.16 ) in the quantity, such as may be caused by changes in liquid level, force direction 306 ( Fig.16 ) caused by the force on the fluid, pressure, force, gas, etc., as discussed in more detail herein. The third sensing element 342 is configured to detect the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ), as discussed in more detail herein. It should be understood that the device configured to detect the measurable medium 304 ( Fig.16 ) is non-limiting, and the third sensing element 342 may be configured to detect a change in the amount of the measurable medium 304 ( Fig.16 ), and the fourth sensing element 344 can be configured to detect the change in the amount of the measurable medium 304 ( Fig.16 ) of the reference value 306a( Fig.16 ). The second bridge 339 outputs a second differential signal 348 from the second node 343. The second differential signal 348 may include the measurable medium 304 ( Fig.16 ) and the reference measurable medium 304a sensed by the third sensing element 342 ( Fig.16 ) related to the differences sensed between the two.

[0102] Additionally, in some embodiments, the first differential signal 346 and the second differential signal 348 are input to a divider 349 to divide or convert the signals into a ratio indicated by a ratiometric output 349a. It should be appreciated that the bridge circuit 332 may have a dual LC oscillator configured to generate two outputs from more than one or separate reservoirs, cans, second pairs of sidewalls or plates, etc. that are compressible and independent of each other.

[0103] As mentioned above, although the non-center-tapped LC circuit differential voltage source structure can be used for a quarter bridge, such a structure can also be used for a half-bridge and full-bridge structure.

[0104] Fig. 17C A single bridge differential circuit 402 is schematically illustrated. The bridge circuit 402 includes a pair of inductors 404, 406, a tail current 408, and a bridge 410. Although illustrated as a pair of inductors 404, 406, this is non-limiting, and the pair of inductors can be a pair of resistors, a pair of capacitors, and / or a combination thereof. The bridge 410 has a node 412 that separates a first pair of sensing elements including a first sensing element 414 and a second sensing element 416, wherein the first sensing element 414 has an incremental change. The first sensing element and the second sensing element 414, 416 can be a pair of inductors, a pair of capacitors, a pair of resistors, and / or a combination thereof. That is, the first sensing element 414 is configured to detect the measurable medium 304 ( Fig.16 ) in the quantity, such as may be caused by changes in liquid level, force direction 306 ( Fig.16 ) caused by the force on the fluid, pressure, gas, etc. The second sensing element 416 is configured to detect the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ), as discussed in more detail herein. It should be understood that the device configured to detect the measurable medium 304 ( Fig.16 ) is non-limiting, and the second sensing element 416 may be configured to detect a change in the amount of the measurable medium 304 ( Fig.16 ), and the first sensing element 414 can be configured to detect the change in the amount of the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 The bridge 410 outputs a differential signal 418 from the node 412. The differential signal 418 may include a signal that is different from the measurable medium 304 sensed by the first sensing element 414 ( Fig.16 ) and the reference measurable medium 304a sensed by the second sensing element 416 ( Fig.16 ) related to the differences sensed between the two.

[0105] Fig.17D A differential bridge circuit 420 having dual bridges 422, 424 is schematically illustrated. The bridge circuit 420 also includes a pair of inductors 426, 427 and a tail current 431. Although illustrated as a pair of inductors 426, 427, this is non-limiting and the pair of inductors 426, 427 may be a pair of resistors, a pair of capacitors, and / or a combination thereof. The first bridge 422 has a first node 428 that separates a first pair of sensing elements including a first sensing element 429 and a second sensing element 430, wherein the first sensing element 429 is variable and has an incremental change.

[0106] That is, the first sensing element 429 is configured to detect a change in the amount of the measurable medium 304, such as may be caused by a change in the liquid level, the force direction 306 ( Fig.16 ) caused by the force on the fluid, pressure, force, gas, etc. The second sensing element 430 is configured to detect the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ), as discussed in more detail herein. It should be understood that the device configured to detect the measurable medium 304 ( Fig.16 ) is non-limiting, and the second sensing element 430 may be configured to detect a change in the amount of the measurable medium 304 ( Fig.16 ), and the first sensing element 429 can be configured to detect the change in the amount of the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ). The first bridge 422 outputs a first differential signal 432 from the first node 428. The first differential signal 432 may include a signal that is different from the measurable medium 304 sensed by the first sensing element 429 and the reference measurable medium 304a sensed by the second sensing element 430 ( Fig.16 ) related to the differences sensed between the two.

[0107] The second bridge 424 has a second node 434 that separates a second pair of sensing elements including a third sensing element 436 and a fourth sensing element 438, wherein the third sensing element 436 is variable and has an incremental change. That is, the third sensing element 436 is configured to detect a change in the amount of measurable medium 304, such as may be caused by a change in liquid level, force direction 306 ( Fig.16 ) or the like, as discussed in more detail herein. The fourth sensing element 438 is configured to detect a reference value 306a of the measurable medium 304a, as discussed in more detail herein. It should be understood that the fourth sensing element 438 is configured to detect a reference value 306a of the measurable medium 304a. Fig.16) is non-limiting, and the fourth sensing element 438 may be configured to detect the change in the amount of the measurable medium 304, while the third sensing element 436 may be configured to detect the reference value 306a of the measurable medium 304. The second bridge 424 outputs a second differential signal 440 from the second node 434. The second differential signal 440 may include a value that is different from the value of the measurable medium 304 ( Fig.16 ) and the reference measurable medium 304a sensed by the fourth sensing element 438 ( Fig.16 ) related to the differences sensed between the two.

[0108] Additionally, in some implementations, the first differential signal 432 and the second differential signal 440 are input to a divider 442 to divide the signals or convert them into a ratio as indicated by a ratio metric output 444 .

[0109] Fig.17E A single bridge ratiometric circuit 450 is schematically illustrated. The bridge circuit 450 includes a pair of sensing elements, the pair of sensing elements including a first sensing element 452 and a second sensing element 454, wherein the first sensing element 452 has an incremental change. Although the first and second sensing elements 452, 454 are illustrated as a pair of inductors, this is non-limiting and may be a pair of resistors, a pair of capacitors, and / or a combination thereof. That is, the first sensing element 452 is configured to detect a change in a quantity in the measurable medium 304, such as may be caused by a change in liquid level, a force direction 306 ( Fig.16 ) caused by the force on the fluid, pressure, force, gas, etc. The second sensing element 454 is configured to detect the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ), as discussed in more detail herein. It should be understood that the device configured to detect the measurable medium 304 ( Fig.16 ) is non-limiting, and the second sensing element 454 may be configured to detect a change in the amount of the measurable medium 304 ( Fig.16 ), and the first sensing element 452 can be configured to detect the change in the amount of the measurable medium 304a ( Fig.16 ) of the reference value 306a( Fig.16 ).

[0110] The bridge circuit 450 also includes a tail current 456 and a bridge 458. The bridge 458 has a node 460 that separates a first element 462 from a second element 464. The first element and the second element 462, 464 can be a pair of inductors, a pair of resistors, a pair of capacitors, and / or a combination thereof. The bridge 458 outputs a ratiometric signal 466 from the node 460. The ratiometric signal 466 can include a ratiometric signal that is proportional to the measurable medium 304 ( Fig.16 ) and the reference measurable medium 304a sensed by the second sensing element 454 ( Fig.16 ) related to the ratio or division difference sensed between the two.

[0111] Return to reference FIG. 17C to FIG. 17D as well as Figure 4 5, it should be understood that the differential bridge circuit 420 can have a dual AC bridge for ratiometric output. The two differential outputs are independent of or eliminate common mode noise commonly found in the transducer and in the circuit through the AC bridge. In addition, the ratiometric output 444 is the ratio of each differential output signal 432, 440. In addition, the ratiometric can be applicable to inductance measurement, capacitance measurement, or resistance measurement. It should be understood that the circuit described herein can remove common mode noise while designing two differential signals.

[0112] Reference now Fig.18 , which schematically illustrates the ratiometric output of the differential capacitive current steering bridge circuit 354, which includes the circuit 230g and the differential capacitive current steering bridge circuit 230f ( Fig.16 ). The current steering bridge circuit 230g includes a voltage source V m 358 and voltage source V' m The sign convention on the voltage sources 358 and 360 indicates the phase of the AC voltage. The differential voltage source drives a bridge that includes a capacitor pair C oil 362 and C ref1 364. It should be understood that although the differential capacitive current steering bridge circuit 230g is illustrated as having a capacitor pair, similar to the above description of Fig.16 While circuit 230f is discussed, this is non-limiting and may be replaced with impedance pairs, resistor pairs, and / or combinations of capacitors, inductors, and resistors.

[0113] The voltage divider is connected to the bridge circuit at node 366 and includes an impedance pair illustrated as capacitor C1 370 and second impedance Z2 372. It should be understood that the impedance pair 370, 372 may be a pair of capacitors, inductors, resistors, any combination thereof, and / or other elements. Capacitor C oil362 can be printed on a PCB and is configured to detect the measurable medium 304 ( Fig.16 ) in the quantity, such as may be caused by changes in liquid level, force direction 306 ( Fig.16 ) caused by the change in the fluid, pressure, gas, etc. In some embodiments, the capacitor C oil 362 and the PCB can be immersed in a fluid, surrounded by a gas, positioned where there is pressure, positioned between compressed media, etc., so that changes in force can be detected. An output that can indicate changes in force, fluid, gas, pressure, etc. is a first differential output 378 obtained from the voltage divider node 374. The same situation can also occur in the reference capacitor 364, so that the output can be compared or the output can be used to define a ratio. It should be understood that the reference can be used to determine dielectric fluids, material creep, etc.

[0114] In this embodiment, the divider 380a can obtain the output V of the differential capacitor current steering bridge circuit 230f. x 356 is divided by the ratio of the output 378 of the differential capacitor current steering bridge circuit 230g to generate a ratiometric output 380. Output V x 356 measures the measurable medium 304, and outputs V ref 378 generates a reference capacitance value from the reference measurable medium 304a. Capacitor C oil The electrodes at 362 may be subjected to forces, pressures, fluids, etc., depending on the application as understood by those skilled in the art. By determining the ratio between output 356 and output 378, the type of force (i.e., caused by gas, fluid, or some other medium), fluid type, temperature, common noise, and electromagnetic interference may now be ignored.

[0115] Thus, according to the present embodiment described above, noise reduction in inductive sensing is accomplished either through RF frequency manipulation of the sensor board or through ratiometric processing of the two output signals.

[0116] According to the above disclosure, the capacitive sensing mechanism of the present invention utilizes ratiometric and differential concepts to eliminate most of the variations associated with undesirable effects, and the differential structure of the sensing element further eliminates most common-mode effects. Other considerations include presenting the ratio of the two signals generated to further reduce common-mode effects. The use of an LC-type driving mechanism further allows for noise immunity and low emissions from driving harmonics.

[0117] It should be understood that the inductive sensor with LC oscillator can be used as part of a current steering bridge pair of a capacitive sensor, which is suitable for detecting liquid level, fluid quality, acceleration, humidity, pressure or some gas concentrations when appropriate impedance, capacitance changes can be detected with respect to gas concentration or any fluid level. In addition, the LC inductive circuit has a good differential voltage source to drive the bridge shown or a modified bridge to measure the quantity in a ratiometric manner to compensate for temperature, electromagnetic interface or mechanical changes of the sensor device.

[0118] Furthermore, it should be understood that discrete components may be substituted for any of the sensing elements described above, including but not limited to capacitors, inductors, or resistors.

[0119] Although specific embodiments have been shown and described herein, it will be appreciated that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. In addition, although various aspects of the claimed subject matter have been described herein, these aspects need not be used in combination. Therefore, the appended claims are intended to cover all such changes and modifications within the scope of the claimed subject matter.

Claims

1. A sensing system using a current steering bridge, the system comprising: processor; A bridge circuit comprising: a pair of differential voltage sources configured to drive the bridge circuit; a first pair of sensing elements that generate a pair of measurement signals that are independent of each other and based on the respective sensing elements, and a second pair of sensing elements communicatively coupled to the first pair of sensing elements, the second pair of sensing elements defining a first divider, the pair of measurement signals being input to respective second sensing elements of the second pair of sensing elements, the first divider being configured to output a first output signal to the processor, wherein the first output signal is a differential signal of the first pair of sensing elements indicative of an amount of measurable medium; and A transducer is communicatively coupled to the bridge circuit, wherein the differential signal output by the first divider is independent of a common mode signal.

2. The system of claim 1, wherein the differential signal is a ratio of the pair of measurement signals.

3. The system of claim 1, wherein the system is integrated into an oscillator of the processor, the oscillator generating radio frequency oscillations.

4. The system of claim 1 , wherein the first pair of sensing elements that generate the pair of measurement signals are capacitors, the second pair of sensing elements are a combination from a set of capacitors, inductors, and resistors, and the pair of measurement signals are differential capacitance measurements corresponding to the force in contact with the bridge circuit.

5. A system according to claim 1, wherein the first pair of sensing elements that generate the pair of measurement signals are capacitors, the second pair of sensing elements are a combination from a group of capacitors, inductors and resistors, and the pair of measurement signals are differential capacitance measurements corresponding to pressure or fluid in contact with the bridge circuit.

6. The system of claim 1 , wherein the first pair of sensing elements that generate the pair of measurement signals are resistors, the second pair of sensing elements are a combination from a set of capacitors, inductors, and resistors, and the pair of measurement signals are differential impedance measurements corresponding to the force in contact with the bridge circuit.

7. A system according to claim 1, wherein the first pair of sensing elements that generate the pair of measurement signals are resistors, the second pair of sensing elements are a combination from a group of capacitors, inductors and resistors, and the pair of measurement signals are differential impedance measurements corresponding to pressure or fluid in contact with the bridge circuit.

8. The system of claim 1 , wherein the first pair of sensing elements that generate the pair of measurement signals are inductors, the second pair of sensing elements are a combination from a set of capacitors, inductors, and resistors, and the pair of measurement signals are differential inductance measurements corresponding to the force in contact with the bridge circuit.

9. A system according to claim 1, wherein the first pair of sensing elements that generate the pair of measurement signals are inductors, the second pair of sensing elements are a combination of a group of capacitors, inductors and resistors, and the pair of measurement signals are differential inductance measurements corresponding to pressure or fluid in contact with the bridge circuit.

10. The system of claim 1, wherein the bridge circuit is a center-tapped LC oscillator configured to drive the first pair of sensing elements.

11. The system of claim 1 , further comprising: a third pair of sensing elements communicatively coupled to the first pair of sensing elements and connected in parallel with the second pair of sensing elements, the third pair of sensing elements defining a second divider, the pair of measurement signals being input to respective third sensing elements of the third pair of sensing elements for outputting a second output signal to the processor, The second output signal is a second differential signal of the first pair of sensing elements.

12. The system of claim 11, wherein the third pair of sensing elements is a combination from a group of capacitors, inductors, and resistors.

13. A sensing system using a current steering bridge, the system comprising: processor; A bridge circuit comprising: a pair of differential voltage sources configured to drive the bridge circuit; a first pair of sensing elements; and a second pair of sensing elements communicatively coupled to the first pair of sensing elements and generating a pair of measurement signals that are independent of each other and based on the respective second sensing elements, the second pair of sensing elements defining a first divider, the first divider being configured to output a first output signal to the processor, wherein the first output signal is a differential signal of the first pair of sensing elements indicative of an amount of measurable medium; and A transducer is communicatively coupled to the bridge circuit, wherein the differential signal output by the first divider is independent of a common mode signal.

14. The system of claim 13, wherein the differential signal is a ratio of the pair of measurement signals.

15. The system of claim 13, wherein the first pair of sensing elements are a combination from a group of capacitors, inductors, and resistors, the second pair of sensing elements that generate the pair of measurement signals are capacitors, and the pair of measurement signals are differential capacitance measurements corresponding to the force of contact with the bridge circuit.

16. The system of claim 13, wherein the first pair of sensing elements are a combination from a group of capacitors, inductors, and resistors, the second pair of sensing elements that generate the pair of measurement signals are resistors, and the pair of measurement signals are differential impedance measurements corresponding to the force in contact with the bridge circuit.

17. The system of claim 13, wherein the first pair of sensing elements are a combination from a group of capacitors, inductors, and resistors, the second pair of sensing elements that generate the pair of measurement signals are inductors, and the pair of measurement signals are differential inductance measurements corresponding to the force in contact with the bridge circuit.

18. A sensing system using a current steering bridge, the system comprising: A bridge circuit comprising: a pair of differential voltage sources configured to drive the bridge circuit; a first pair of sensing elements; and a second pair of sensing elements communicatively coupled to the first pair of sensing elements and generating a first pair of measurement signals, the first pair of measurement signals being independent of each other and based on the respective second sensing elements, the second pair of sensing elements defining a first divider, the first divider being configured to output a first output signal, a third pair of sensing elements communicatively coupled to the first pair of sensing elements and connected in parallel with the second pair of sensing elements, the third pair of sensing elements generating a second pair of measurement signals that are independent of each other and based on respective third sensing elements, the third pair of sensing elements defining a second divider, the second divider being configured to output a second output signal, The first output signal and the second output signal are connected to a divider, the divider provides a ratiometric output, and the ratiometric output is independent of common mode noise.

19. The system of claim 18, wherein: The first pair of sensing elements is a combination of a capacitor, an inductor and a resistor, the second pair of sensing elements generating the first pair of measurement signals are capacitors, The third pair of sensing elements generating the second pair of measurement signals are capacitors, and The first pair of measurement signals and the second pair of measurement signals are differential capacitance measurements corresponding to a force in contact with the bridge circuit.

20. A sensing system using a current steering bridge, the system comprising: processor; A bridge circuit comprising: a pair of differential voltage sources configured to drive the bridge circuit; a first pair of sensing elements that generate a pair of measurement signals that are independent of each other and based on the respective sensing elements, and a second pair of sensing elements communicatively coupled to the first pair of sensing elements, the second pair of sensing elements defining a first divider, the pair of measurement signals being input to respective second sensing elements of the second pair of sensing elements, the first divider being configured to output a first output signal to the processor, wherein the first output signal is a differential signal of the first pair of sensing elements; a third pair of sensing elements communicatively coupled to the first pair of sensing elements and connected in parallel with the second pair of sensing elements, the third pair of sensing elements defining a second divider, the pair of measurement signals being input to respective third sensing elements of the third pair of sensing elements for outputting a second output signal to the processor, The second output signal is a second differential signal of the first pair of sensing elements.

Images