Sensing system based on low-energy resistor

Abstract

The invention relates to a sensing system based on low energy resistance. An example apparatus, computer-implemented method, and computer program product are provided for determining a variable resistance of a conductive portion of a resistance-based sensing device. An example apparatus includes a resistance-based sensing device having a conductive portion configured to indicate a physical characteristic of an environment based on a variable resistance of the conductive portion. The apparatus also includes a controller electrically coupled to the resistance-based sensing device, the controller having a processor and a memory device storing instructions that, when executed by the processor, are operable to cause the processor to transfer stored energy from the energy storage device to the conductive portion of the resistance-based sensing device, a time interval associated with a voltage drop in the energy storage device is determined, and a variable resistance of a conductive portion of the resistance-based sensing device is determined based at least in part on the time interval.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to resistance-based sensing systems, and more particularly to resistance-based sensing systems configured for low energy consumption. Background Art

[0002] Many sensors use changes in electrical resistance to determine physical properties of the surrounding environment. For example, due to the piezoresistive effect, the electrical resistance of a material may change when subjected to mechanical strain. Using this effect, pressure sensors, strain gauges, and other sensors can be designed to measure changes in electrical resistance and convert this resistance into a physical measurement. Furthermore, temperature sensors (such as resistance thermometers) can use changes in the electrical resistance of a conductive material to determine the temperature of the surrounding environment.

[0003] Applicants have identified a number of technical challenges and difficulties associated with determining physical characteristics of an environment based on variable resistors. Through applied effort, ingenuity, and innovation, Applicants have addressed the problems associated with determining physical characteristics of an environment based on variable resistors by developing the solutions embodied in the present disclosure, which are described in detail below. Summary of the Invention

[0004] Various embodiments relate to an example apparatus, computer-implemented method, and computer program product for determining a variable resistance of a conductive portion of a resistance-based sensing device. An example apparatus may include a resistance-based sensing device including a conductive portion, the resistance-based sensing device configured to indicate a physical characteristic of an environment based on the variable resistance of the conductive portion. The example apparatus may also include a controller electrically coupled to the resistance-based sensing device, the controller including one or more processors and one or more memory devices storing instructions that, when executed by the one or more processors, are operable to cause the one or more processors to: transfer stored energy from an energy storage device to the conductive portion of the resistance-based sensing device; determine a time interval associated with a voltage drop across the energy storage device; and determine the variable resistance of the conductive portion of the resistance-based sensing device based at least in part on the time interval.

[0005] In some embodiments, the apparatus further includes an energy harvester configured to generate harvested energy and transmit the harvested energy to the energy storage device.

[0006] In some embodiments, the energy harvester generates harvested energy from a natural power source.

[0007] In some embodiments, the natural power source is at least one of solar energy, thermal energy, wind energy, and vibration energy.

[0008] In some embodiments, the physical property indicated by the resistance-based sensing device is at least one of pressure, strain, temperature, and light.

[0009] In some embodiments, the apparatus further includes a low power timer electrically coupled to the controller and configured to generate a count value based on a clock frequency of the controller.

[0010] In some embodiments, the time interval is determined based on the count value.

[0011] In some embodiments, the apparatus further includes a supply voltage detector electrically coupled to the controller and configured to determine a voltage value in the energy storage device.

[0012] In some embodiments, the voltage drop corresponds to a difference between a first voltage value and a second voltage value determined by the supply voltage detector.

[0013] In some embodiments, the second voltage value is associated with a minimum operating voltage of the controller.

[0014] In some embodiments, the apparatus further comprises a reference resistor having a known resistance value.

[0015] In some embodiments, a variable resistance of a conductive portion of a resistance-based sensing device is determined based at least in part on a reference time interval associated with a reference voltage drop in the energy storage device while stored energy from the energy storage device is transferred to a reference resistor.

[0016] In some embodiments, the apparatus further includes a transceiver electrically coupled to the controller.

[0017] In some embodiments, a time interval representing a variable resistance of a conductive portion of the resistance-based sensing device is transmitted by a transceiver radio.

[0018] In some embodiments, the variable resistance of the conductive portion of the resistance-based sensing device is determined without the use of an analog-to-digital converter.

[0019] A computer-implemented method for determining a variable resistance of a conductive portion of a resistance-based sensing device is also provided. In some embodiments, the computer-implemented method includes: transferring stored energy from an energy storage device to the conductive portion of the resistance-based sensing device via a controller; determining a time interval associated with a voltage drop across the energy storage device; and determining the variable resistance of the conductive portion of the resistance-based sensing device based at least in part on the time interval.

[0020] In some embodiments, the computer-implemented method further includes determining a count value based on a low power timer electrically coupled to the controller and configured to increment the count value based on a clock frequency of the controller, wherein the time interval is determined based on the count value.

[0021] In some embodiments, the computer-implemented method further includes a power supply voltage detector electrically coupled to the controller and configured to determine a voltage value in the energy storage device.

[0022] In some embodiments, the computer-implemented method further includes determining, by a power supply voltage detector, a first voltage value and a second voltage value, wherein the voltage drop corresponds to a difference between the first voltage value and the second voltage value, and wherein the second voltage value is associated with a minimum operating voltage of the controller.

[0023] A computer program product for determining a variable resistance of a conductive portion of a resistance-based sensing device is also provided. In some embodiments, the computer program product includes at least one non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions including an executable portion configured to: transfer stored energy from an energy storage device to the conductive portion of the resistance-based sensing device via a controller; determine a count value based on a low-power timer electrically coupled to the controller and configured to increment the count value based on a clock frequency of the controller; determine a time interval associated with a voltage drop in the energy storage device based at least in part on the count value; and determine the variable resistance of the conductive portion of the resistance-based sensing device based at least in part on the time interval. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Reference will now be made to the accompanying drawings. In certain embodiments described herein, components shown in the accompanying drawings may or may not be present. According to example embodiments of the present disclosure, some embodiments may include fewer (or more) components than shown in the drawings.

[0025] Figure 1 illustrates an example block diagram of an exemplary low-energy resistance-based sensing system according to an example embodiment of the present disclosure;

[0026] Figure 2 illustrates an example block diagram of an example controller in a low-energy resistance-based sensing system according to an example embodiment of the present disclosure;

[0027] Figure 3 illustrates the collection states of an example embodiment of a low energy resistance-based sensing system according to an example embodiment of the present disclosure;

[0028] Figure 4illustrates active states of an example embodiment of a low energy resistance-based sensing system according to an example embodiment of the present disclosure;

[0029] Figure 5 illustrates an exemplary resistance-based sensing device configured to measure pressure according to an example embodiment of the present disclosure;

[0030] Figure 6 An example graph illustrating example rise and fall times of a storage voltage of a low energy resistance-based sensing system according to an example embodiment of the present disclosure;

[0031] Figure 7 an example graph illustrating a plurality of example fall times as a function of variable resistance according to an example embodiment of the present disclosure; and

[0032] Figure 8 An example flow chart for determining a variable resistance of a conductive portion of a resistance-based sensing device according to an example embodiment of the present disclosure is illustrated. DETAILED DESCRIPTION

[0033] Example embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the presently disclosed invention are shown. Indeed, the presently disclosed embodiments may be embodied in many different forms and should not be construed as limited to the embodiments described herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0034] Various example embodiments address technical issues associated with determining the variable resistance of a conductive portion of a resistance-based sensing device, where the resistance of the conductive portion varies based on physical properties of a surrounding environment. As will be appreciated, there are many example scenarios where determining physical properties of a surrounding environment based on the variable resistance at a resistance-based sensing device may be beneficial.

[0035] Typically, resistance-based sensors use changes in the resistance of the conductive portion of a resistance-based sensing device to determine physical properties of the surrounding environment. For example, due to the piezoresistive effect, the resistance of a conductive material may change when subjected to mechanical strain. Using the piezoresistive effect, pressure, strain, stress, and other forces applied from the surrounding environment to the conductive portion of a resistance-based sensing device can be measured and converted into physical properties. In addition, temperature sensors (such as resistance thermometers) can use changes in the resistance of a conductive material to determine the temperature of the surrounding environment. Similarly, light sensors can measure the change in resistance at a conductive surface due to the reception of photons at the surface, thereby determining the light intensity in the surrounding environment.

[0036] Each of these resistance-based sensors utilizes a measurement of the variable resistance of a conductive portion of a resistance-based sensing device to determine a relevant physical property. The resistance of the conductive material can be determined, and the relevant physical property can be calculated based on the variable resistance. In some examples, a voltage divider (such as a Wheatstone bridge configuration) is utilized to determine the change in resistance of the material being measured. The voltage divider typically requires an excitation voltage and an analog-to-digital converter (ADC) to determine the resistance and relevant physical property of the conductive portion of the resistance-based sensing device. The power for operating the analog-to-digital converter, the excitation voltage, and other components of the resistance-based sensor typically requires a large amount of power source, such as a battery or power supply.

[0037] Many resistance-based sensors use changes in electrical resistance to determine physical properties of their surroundings. These sensors are located in inaccessible, remote, or inconvenient environments. This makes maintenance of resistance-based sensors difficult or impossible. Furthermore, many resistance-based sensors are deployed in large numbers, making individual sensor maintenance difficult to maintain. One of the primary sources of maintenance is batteries, which may need to be replaced periodically to maintain sensor operation.

[0038] Therefore, there is a need to periodically measure the resistance change of a variable resistor and transmit the resistance change to a remote computing entity without a battery and without using an analog-to-digital converter or other power-consuming electrical components.

[0039] Various example embodiments described herein utilize various techniques to determine the variable resistance of a conductive portion of a resistance-based sensing device associated with a physical characteristic of an environment. For example, in some embodiments, a controller can transfer a portion of the stored energy through the conductive portion of the resistance-based sensing device and determine the variable resistance of the conductive portion of the resistance-based sensing device based at least in part on a time interval associated with a voltage drop in the energy storage device. Utilizing a supply voltage detector and a low-power timer, a low-energy resistance-based sensing system can use a digital count value to determine the time interval associated with the voltage drop in the energy storage device, thereby eliminating the need for an ADC. The reduction in power required to determine the variable resistance of the resistance-based sensing device enables the low-energy resistance-based sensing system to operate using energy from an electrostatic-based energy storage device (such as a capacitor), thereby eliminating the need for a battery.

[0040] As a result of the example embodiments described herein, in some examples, the effectiveness of resistance-based sensors can be greatly improved. For example, a low-energy resistance-based sensing system can be configured to determine the variable resistance of a conductive portion of a resistance-based sensing device without an ADC and a battery. Eliminating the battery and ADC can significantly reduce the size and area of ​​the low-energy resistance-based sensing system. The reduction in size and area of ​​the low-energy resistance-based sensing system can enable the low-energy resistance-based sensing system to be deployed in a variety of environments that require low-profile, hidden, unique shapes, or other unique deployment environments. For example, smart materials and / or smart bolts can be manufactured and deployed using a low-energy resistance-based sensing system.

[0041] Furthermore, the elimination of various electrical components (including batteries) can reduce the maintenance required to maintain the low-energy resistance-based sensing system, thereby enabling its deployment in environments that may be difficult to access. Little or no maintenance can further enable the deployment of large numbers of low-energy resistance-based sensing systems without having to worry about unmaintainable maintenance. Furthermore, the low-energy resistance-based sensing system according to the present disclosure can improve the life expectancy and stability of the low-energy resistance-based sensing system. The improvement in life expectancy and stability further enables its deployment in large numbers in difficult-to-access environments.

[0042] Now refer to Figure 1 , an exemplary low energy resistance-based sensing system 100 is provided. Figure 1 As shown, the exemplary low energy resistance-based sensing system 100 includes an energy harvester 104 electrically coupled to an energy storage device 106 and a controller 102, the energy harvester 104 being configured to generate harvested energy 112. Figure 1 As further shown, the controller 102 is electrically coupled to the reference resistor 110 and the resistance-based sensing device 108 .

[0043] like Figure 1 As shown, the exemplary low-energy resistance-based sensing system 100 includes an energy harvester 104. The energy harvester 104 is any device configured to harvest energy from the surrounding environment and convert the energy into electrical energy (e.g., harvested energy 112). The energy harvester 104 can obtain energy from various external sources, such as solar energy from the sun, thermal energy from temperature changes, wind energy, kinetic energy from motion and / or vibration, or any other ambient energy source. Generally, the energy harvester 104 converts ambient energy from the surrounding environment into electrical energy (e.g., harvested energy 112) that is stored by the energy storage device 106 and / or utilized by the controller 102 or other electrical components of the low-energy resistance-based sensing system 100.

[0044] like Figure 1As further shown, the exemplary low energy resistance-based sensing system 100 includes an energy storage device 106. The energy storage device 106 is any device configured to accumulate stored energy from the harvested energy 112 generated by the energy harvester 104. For example, the energy storage device 106 may include a capacitor, a supercapacitor, a battery, a fuel cell, or other device configured to store electrical energy in another form. In some embodiments, the energy storage device 106 may include a passive electrical component, such as a capacitor. Passive electrical components reduce maintenance and increase the life expectancy of electrical components. The low energy resistance-based sensing system 100 according to the present disclosure may be configured to operate on power stored in a passive electrical component, such as a capacitor. Embodiments utilizing a capacitor as the energy storage device 106 will be combined with Figure 3 Further description.

[0045] like Figure 1 As further shown, the exemplary low-energy resistance-based sensing system 100 includes a controller 102. The controller 102 is any computing device including hardware and / or software configured to utilize harvested energy 112 stored in the energy storage device 106 to determine the variable resistance of the conductive portion of the resistance-based sensing device 108 based on a time interval associated with a voltage drop in the energy storage device 106. For example, the controller 102 can be configured to monitor the voltage in the energy storage device 106. Figure 3 As further shown, the controller 102 can periodically measure the voltage in the energy storage device 106 during the collection state. In the event that the voltage in the energy storage device 106 reaches a predetermined voltage threshold, the controller 102 can enter an active state in which the controller 102 measures the variable resistance of the resistance-based sensing device 108, performs calibration based on the measurement of the reference resistor 110, and / or performs other tasks related to the operation of the low-energy resistance-based sensing system 100, such as transmitting recorded and / or stored data. The controller 102 will Figure 2 Further discussion.

[0046] like Figure 1 As further shown, the exemplary low-energy resistance-based sensing system 100 includes a resistance-based sensing device 108. The resistance-based sensing device 108 is any device having a conductive portion that is configured to exhibit a variable resistance (e.g., a variable resistor) based on a change in a physical property of the environment surrounding the resistance-based sensing device 108. A physical property refers to any measurable property of a surface, material, atmosphere, space, or other medium. The physical property may include temperature, pressure, stress, force, strain, light, etc. The resistance of the conductive portion of the resistance-based sensing device 108 may change based on the change in the physical property.

[0047] For example, the conductive portion of the resistance-based sensing device 108 may include a pressure-sensing diaphragm formed of a semiconductor material that is configured to deform under pressure applied to a surface of the pressure-sensing diaphragm. The deflection of the pressure-sensing diaphragm generates a variable resistance in the pressure-sensing diaphragm that corresponds to the pressure applied to the surface. Thus, measurement of the variable resistance of the pressure-sensing diaphragm can be used to determine the pressure in the surrounding environment.

[0048] Similarly, a resistance thermometer can utilize a resistance-based sensing device 108 to determine the temperature of an environment or surface. In one example, a conductive portion (such as a platinum wire) can exhibit a variable resistance that corresponds to the temperature of the surrounding environment. Therefore, measurement of the variable resistance of the platinum wire can be used to determine the temperature of the surrounding environment.

[0049] In another example, the resistance of a material can vary based on the stress on the material and / or surface (e.g., a variable resistance). Stress can be any force present during deformation of a material. For example, stress can include tension, compression, shear, bending, and / or torsion. Each of these forces can change the variable resistance of a material, surface, and / or conductive portion integrated with the material and / or surface. Therefore, measurement of the variable resistance of a conductive portion of a material and / or surface can be used to determine the stress on the material and / or surface.

[0050] like Figure 1 As further shown, the exemplary low-energy resistance-based sensing system 100 includes a reference resistor 110. The reference resistor 110 can be any conductive object, item, structure, material, etc. having a known resistance value. For example, the reference resistor 110 can include a resistor having a known and / or programmable value or a variable resistor. The reference resistor 110 can be used to calibrate the low-energy resistance-based sensing system 100. For example, before and / or during operation, stored energy in the energy storage device 106 can be transferred to the reference resistor 110. The controller 102 can determine a reference time interval representing a time interval associated with a reference voltage drop across the energy storage device 106 when current is transferred from the energy storage device 106 and through the reference resistor 110. The reference time interval can be compared to a measured time interval of the variable resistance of the conductive portion of the resistance-based sensing device 108 to determine the resistance value of the conductive portion of the resistance-based sensing device 108.

[0051] In some embodiments, the reference time interval corresponding to the reference voltage drop can be periodically measured during operation. By periodically measuring the reference time interval and recalibrating based on the resistance value of the reference resistor 110, environmental changes such as temperature, humidity, and other environmental changes can be taken into account.

[0052] Now refer to Figure 2 , depicts a block diagram of an example controller 202 . Figure 2 An example controller 202 is illustrated in accordance with at least some example embodiments of the present disclosure. Controller 202 includes a processor 203, input / output circuitry 204, a data storage medium 206, communication circuitry 208, a transceiver radio circuitry 220, a supply voltage detector circuitry 222, and a low power timer circuitry 224. In some embodiments, controller 202 is configured to implement and perform the operations described herein using one or more of the sets of circuitry 203, 204, 206, 208, 220, 222, and / or 224.

[0053] Although components are described with respect to functional limitations, it should be understood that specific implementations necessarily include the use of specific computing hardware. It should also be understood that, in some embodiments, certain components described herein include similar or general-purpose hardware. For example, two sets of circuit systems can utilize the same (multiple) processors, (multiple) network interfaces, (multiple) storage media, etc. to perform their related functions, thereby not requiring duplicate hardware for each set of circuit systems. Therefore, users of the term "circuitry" used herein with respect to components of the apparatus described herein should be understood to include specific hardware configured to perform the functions associated with the specific circuitry described herein.

[0054] In particular, the term "circuitry" should be broadly understood to include hardware and, in some embodiments, software for configuring the hardware. For example, in some embodiments, "circuitry" includes processing circuitry, storage media, network interfaces, input / output devices, and the like. Alternatively or additionally, in some embodiments, other elements of controller 202 provide or supplement the functionality of other specific groups of circuitry. For example, in some embodiments, processor 203 provides processing functionality to any group of circuitry, data storage media 206 provides storage functionality to any group of circuitry, communications circuitry 208 provides network interface functionality to any group of circuitry, and so on.

[0055] In some embodiments, the processor 203 (and / or a coprocessor, or auxiliary processor, or any other processing circuitry otherwise associated with the processor) communicates with the data storage medium 206 via a bus to transfer information between components of the controller 202. In some embodiments, for example, the data storage medium 206 is non-transitory and may include, for example, one or more volatile and / or non-volatile memories. In other words, for example, in some embodiments, the data storage medium 206 includes or embodies an electronic storage device (e.g., a computer-readable storage medium). In some embodiments, the data storage medium 206 is configured to store information, data, content, applications, instructions, etc. to enable the controller 202 to perform various functions according to example embodiments of the present disclosure.

[0056] The processor 203 can be implemented in a variety of different ways. For example, in some example embodiments, the processor 203 includes one or more processing devices configured to execute independently. Additionally or alternatively, in some embodiments, the processor 203 includes one or more processors configured in series via a bus to implement independent execution of instructions, pipelining, and / or multithreading. The use of the terms "processor" and "processing circuitry" should be understood to include a single-core processor, a multi-core processor, multiple processors within the controller 202, and / or one or more remote or "cloud" processors external to the controller 202.

[0057] In an example embodiment, the processor 203 is configured to execute instructions stored in the data storage medium 206 or otherwise accessible to the processor. Alternatively or additionally, in some embodiments, the processor 203 is configured to execute hard-coded functions. Therefore, whether configured by hardware methods or software methods, or by a combination thereof, the processor 203 represents an entity (e.g., physically embodied in a circuit system) that is capable of performing operations according to embodiments of the present disclosure while being configured accordingly. Alternatively or additionally, as another example in some example embodiments, when the processor 203 is embodied as an executor of software instructions, the instructions specifically configure the processor 203 to perform an algorithm embodied in a specific operation described herein when such instructions are executed.

[0058] In some embodiments, the controller 202 includes an input / output circuit system 204 that provides output to the user and, in some embodiments, receives an indication of user input. In some embodiments, the input / output circuit system 204 communicates with the processor 203 to provide this functionality. The input / output circuit system 204 may include one or more user interfaces (e.g., user interfaces), and in some embodiments, includes a display that includes (multiple) interfaces presented as a network user interface, an application user interface, a user device, a back-end system, etc. The processor 203 and / or the input / output circuit system 204 including the processor may be configured to control one or more functions of one or more user interface elements by computer program instructions (e.g., software and / or firmware) stored on a memory accessible to the processor (e.g., a data storage medium 206, etc.). In some embodiments, the input / output circuit system 204 includes or utilizes a user-oriented application to provide input / output functionality to a client device and / or other displays associated with the user.

[0059] In some embodiments, controller 202 includes communication circuitry 208. Communication circuitry 208 comprises any device, such as a device or circuitry embodied in hardware or a combination of hardware and software, configured to receive and / or transmit data from / to a network and / or any other device, circuit, or module in communication with controller 202. In this regard, for example, in some embodiments, communication circuitry 208 comprises a network interface for enabling communication with a wired or wireless communication network. Additionally or alternatively, in some embodiments, communication circuitry 208 comprises one or more network interface cards, antennas, buses, switches, routers, modems, and supporting hardware, firmware, and / or software, or any other device suitable for enabling communication via one or more communication networks. Additionally or alternatively, communication circuitry 208 comprises circuitry for interacting with antenna(s) and / or other hardware or software to cause transmission of signals via the antenna(s) or to process reception of signals received via the antenna(s). In some embodiments, communication circuitry 208 enables transmission of data to and / or reception of data from client devices in communication with controller 202.

[0060] The transceiver radio circuitry 220 includes hardware, software, firmware, and / or a combination thereof that supports various functions associated with sending and receiving messages according to a wireless communication protocol. For example, the transceiver radio circuitry 220 can be configured to support the transmission and reception of messages according to Bluetooth, Bluetooth Low Energy (LE), ZigBee, LTE, 5G, Wi-Fi, or another wireless communication protocol. In some embodiments, the transceiver radio circuitry 220 can be configured to periodically transmit a signal to a resistance-based sensing device (e.g., Figure 1 The receiving device may also transmit data associated with a variable resistance of the resistance-based sensing device 108 (shown in FIG. 1 ). For example, the determined variable resistance, the measured time interval, the configured voltage drop, the reference time interval, the configured reference voltage drop, a clock count associated with the time interval and the reference time interval, a clock frequency of the processor 203, etc. In some embodiments, the receiving device may be configured to determine the time interval and / or the variable resistance based on the transmitted data.

[0061] Additionally, transceiver radio circuitry 220 may be configured to receive messages according to a wireless communication protocol. For example, a remote computing device may transmit configuration data including a frequency for measuring the variable resistance and / or a speed for transmitting the determined variable resistance.

[0062] Supply voltage detector circuitry 222 includes electrical components that support electrical connections to the measurement circuitry, such as energy storage devices (e.g., Figure 1 The power supply voltage detector circuit system 222 can be used to trigger a transition between a collection state and an active state of the low energy resistance-based sensing system based on the voltage value of the energy storage device. For example, a maximum voltage (e.g., a first voltage value) can be configured. In some embodiments, the maximum voltage can be associated with the maximum voltage capacity of the energy storage device. In the event that the voltage value of the energy storage device reaches or exceeds the maximum voltage, the low energy resistance-based sensing system can transition from the collection state to the active state. During the active state, the low energy resistance-based sensing system can utilize the stored energy in the energy storage device to perform tasks such as measuring the variable resistance of the resistance-based sensing device, measuring a reference time interval associated with a reference resistor, transmitting data through the transceiver radio circuit system 220, and the like. The active state will be combined with Figure 4 Further description.

[0063] The low energy resistance-based sensing system can also be configured with a minimum voltage (e.g., a second voltage value). The minimum voltage can be associated with a minimum voltage required to operate the low energy resistance-based sensing system. When the minimum voltage is detected, the low energy resistance-based sensing system can transition to an energy harvesting state in which the harvested energy is directed to the energy storage device. The energy harvesting state will be combined with Figure 3 Further description.

[0064] The low power timer circuit system 224 includes hardware, software, firmware and / or a combination thereof that supports various functions associated with incrementing the count value. The count value can be configured to increment relative to the clock frequency of the processor 203. The count value of the low power timer circuit system 224 can be used to determine a transmission interval, determine a measurement interval of a voltage value on the energy storage device, and the like. In addition, the count value can be used to measure a time interval of a voltage drop in the energy storage device to determine a reference time interval on a resistance-based sensing device and a variable resistance of a conductive component. For example, in a case where the harvested energy stored in the energy storage device is transferred to a resistance-based sensing device, a count value associated with a voltage drop from a maximum voltage to a minimum voltage of the energy storage device can be determined. The count value can be used to determine the variable resistance of the resistance-based sensing device. The determination of the variable resistance based on the count value will be related to Figure 6-Figure 7 Further description.

[0065] Additionally or alternatively, in some embodiments, one or more of the groups of circuit systems 203-224 are combinable. Additionally or alternatively, in some embodiments, one or more of the groups of circuit systems perform a portion or all of the functions associated with another component. For example, in some embodiments, one or more of the groups of circuit systems 203-224 are combined into a single module embodied in hardware, software, firmware, and / or a combination thereof. Similarly, in some embodiments, one or more of the groups of circuit systems (e.g., transceiver radio circuit system 220, supply voltage detector circuit system 222, and / or low power timer circuit system 224) are combined so that processor 203 individually performs one or more of the operations described above with respect to each of these circuit systems.

[0066] Now refer to Figure 3 , an exemplary low energy resistance-based sensing system 300 in an energy harvesting state is provided. Figure 3 As shown, an exemplary low energy resistance-based sensing system 300 includes an energy harvester 304 electrically coupled to an energy storage device (eg, a storage capacitor 306) and a controller 302, the energy harvester 304 being configured to generate harvested energy 312. Figure 3 As further shown, controller 302 is electrically coupled to reference resistor 310 and resistance-based sensing device 308. Depicted controller 302 includes supply voltage detector circuitry 322, low power timer circuitry 324, and transceiver radio circuitry 320.

[0067] exist Figure 3In the harvesting state shown, harvested energy 312 is transferred to a storage capacitor 306. The storage capacitor 306 is one or more passive electrical components configured to store electrical energy in an electric field by accumulating charge on two enclosed conductive surfaces separated by a dielectric. Figure 3 As shown, the accumulated charge generates a storage voltage 330. The storage voltage 330 represents the potential difference between the two plates of the storage capacitor 306.

[0068] During the collection state, the controller 302 remains in the sleep state to utilize a minimal amount of power. For example, the controller 302 can utilize the low-power timer circuitry 324 to determine how often the supply voltage detector circuitry 322 can measure the storage voltage 330. The low-power timer circuitry 324 can be configured to utilize negligible power on the order of picowatts. The supply voltage detector circuitry 322 can periodically measure the storage voltage 330 to determine whether a maximum voltage has been reached that signals a transition from the collection state to the active state. Because the activity of the controller 302 is minimized, the controller 302 can utilize microwatts of power during the sleep state. Therefore, the harvested energy 312 is primarily used to establish the storage voltage 330 by charging the storage capacitor 306.

[0069] When the stored voltage 330 reaches a maximum voltage, the low-energy resistance-based sensing system 300 can transition to an active state. The maximum voltage is any voltage that the controller 302 is configured to transition to the active state. For example, the maximum voltage can be the storage capacity of the storage capacitor 306. Alternatively, the maximum voltage can be a voltage required to perform a specific function, such as measuring the variable resistance of the resistance-based sensing device 308, measuring the resistance of the reference resistor 310, and / or performing controller 302 functions, such as transmitting data using the transceiver radio circuitry 320.

[0070] Now refer to Figure 4 , an exemplary low energy resistance-based sensing system 400 in an active state is provided. Figure 4 As shown, an exemplary low energy resistance-based sensing system 400 includes an energy harvester 404 electrically coupled to an energy storage device (e.g., a storage capacitor 406) and a controller 402 configured to receive stored energy 440 from the storage capacitor 404. Figure 4 As further shown, controller 402 is electrically coupled to reference resistor 410 and resistance-based sensing device 408. Depicted controller 402 includes supply voltage detector circuitry 422, low power timer circuitry 424, and transceiver radio circuitry 420.

[0071] exist Figure 4In the active state shown, the storage voltage 430 has reached a maximum voltage and stored energy 440 is transferred from the storage capacitor 406 to the controller 402. During the active state, the controller 402 utilizes the supply voltage detector circuitry 422 to monitor the storage voltage 430, which represents the stored energy in the storage capacitor 406. In the event that the minimum voltage is reached, the controller transitions back to the active state. Figure 3 The energy harvesting state is shown, and the harvested energy is transferred to the storage capacitor 406. The minimum voltage is any voltage at which the controller 402 is configured to transition to the energy harvesting state. For example, the minimum voltage may be the minimum operating voltage of the controller 402.

[0072] The controller 402 can perform a number of functions during the active state. For example, the controller 402 can transfer stored energy 440 to the reference resistor 410 and perform calibration measurements to determine a reference time interval based on the resistance value of the reference resistor 410. In another example, the controller 402 can transfer stored energy 440 to the resistance-based sensing device 408 and determine the variable resistance of the resistance-based sensing device 408 by determining a time interval associated with a voltage drop from a maximum voltage to a minimum voltage and determining the variable resistance based on the reference time interval. In another example, the controller 402 can transmit one or more data values ​​representing the observed variable resistance value using the transceiver radio circuitry 420.

[0073] In some embodiments, the controller 402 may be configured to perform multiple operations during a single active state. In some embodiments, the controller 402 may alternate the functions performed from one active state to the next. In the event that the storage voltage 430 measured by the supply voltage detector circuitry 422 reaches a minimum voltage, the controller 402 transitions back to the active state. Figure 3 Energy harvesting states shown.

[0074] Now refer to Figure 5 , an exemplary resistance-based sensing device 508a, 508b is provided. The resistance-based sensing device 508a, 508b depicts a non-limiting example of how a physical characteristic of the external environment (e.g., pressure 556) can change the resistance value of the conductive portion 558a, 558b of the resistance-based sensing device 508a, 508b.

[0075] like Figure 5As shown, resistance-based sensing devices 508a, 508b include conductive portions 558a, 558b having conductive particles 552a, 552b. The density of conductive particles 552a, 552b determines the conductivity of conductive portions 558a, 558b. The higher the density of conductive particles 552a, 552b, the higher the conductivity of conductive portions 558a, 558b. Conversely, the higher the density of conductive particles 552a, 552b, the lower the resistance of conductive portions 558a, 558b. Therefore, ambient pressure 556 can be measured based on the change in resistance of conductive portions 558a, 558b of resistance-based sensing devices 508a, 508b.

[0076] For example, Figure 5 As shown, when pressure 556 is applied to the surface of resistance-based sensing device 508b, the surface of resistance-based sensing device 508b is displaced a distance 554. The displacement of the surface of resistance-based sensing device 508b increases the density of conductive particles 552b in resistance-based sensing device 508b and decreases the resistance value of conductive portion 558b of resistance-based sensing device 508b.

[0077] like Figure 5 As further shown, the conductive portions 558a, 558b of the resistance-based sensing devices 508a, 508b include a pair of electrodes 550a, 550b. The pair of electrodes 550a, 550b enables current to be transmitted through the conductive portions 558a, 558b of the resistance-based sensing devices 508a, 508b. Measuring the time interval associated with the voltage drop across the energy storage device as current is transmitted through the conductive portions 558a, 558b of the resistance-based sensing devices 508a, 508b can enable the determination of the resistance value associated with the conductive portions 558a, 558b and thereby determine a physical characteristic of the external environment (e.g., pressure 556).

[0078] Figure 5 This section describes a non-limiting example of how the physical characteristics of the external environment can alter the resistance of the conductive portion of a resistance-based sensing device. However, there are many ways in which the physical characteristics of the external environment can alter the resistance of the conductive portion of a resistance-based sensing device. For example, temperature, tension, shear, bending, and / or torsional forces can all affect the density of conductive particles in the conductive portion of a resistance-based sensing device.

[0079] Now refer to Figure 6 , depicts an example graph 660 depicting changes in a storage voltage 630 in an energy storage device (eg, energy storage device 106 , storage capacitors 306 , 406 ) with respect to time 666 during an energy harvesting state 661 and an active state 663 .

[0080] like Figure 6 As shown, during the energy harvesting state 661, the controller of the low-energy resistance-based sensing system (e.g., controller 102, 202, 302, 402) enters a sleep state. During the sleep state, the low-power timer (e.g., low-power timer circuitry 224, 324, 424) and the supply voltage detector (e.g., supply voltage detector circuitry 222, 322, 422) are the main energy consumers. Therefore, the power consumption during the energy harvesting state 661 is low, which allows the storage voltage 630 to be established in the energy storage device. For example, as Figure 6 As shown, at the beginning of energy harvesting state 661, storage voltage 630 is at or near minimum voltage 664. However, at the end of energy harvesting state 661, storage voltage 630 is at or near maximum voltage 662. The time interval associated with the increase of storage voltage 630 from minimum voltage 664 to maximum voltage 662 is rise time 667. The more energy harvested by the energy harvester (e.g., energy harvester 104, 304, 404), the faster rise time 667. Similarly, the less power used by the low-energy resistance-based sensing system, the faster rise time 667.

[0081] like Figure 6 As further shown, during the active state 663 , the storage voltage 630 experiences a voltage drop 665 from a maximum voltage 662 to a minimum voltage 664 . Figure 6 The voltage drop 665 shown is the voltage drop across the energy storage device due to energy dissipation primarily through the resistance-based sensing device (eg, resistance-based sensing device 108 , 308 , 408 , 508 ). Figure 6 The fall time 668 shown is the time interval associated with the voltage drop 665 during the active state 663 .

[0082] The fall time 668 may be based on the resistance value of the conductive portion of the resistance-based sensing device (eg, the variable resistor R var ) varies. The fall time 668 can be determined based on the output of the low power timer and the supply voltage detector. For example, during the active state of the controller, the low power timer can be set based on the counter frequency (f counter ) continuously updates the count value relative to the controller clock frequency (count lpt). In some embodiments, the count value may be incremented at each clock cycle, every other clock cycle, or some other regular interval based on the clock of the low power timer. During operation, the count value may be reinitialized (e.g., set to zero) at the beginning of the active state 663. The count value may be updated according to the counter frequency for the duration of the active state 663. In the event that the storage voltage 630 is less than or equal to the minimum voltage 664, the controller may transition to the energy harvesting state 661 and the count value may stop. The fall time 668 (t fall ) can be based on the count value of the low power timer (count lpt ) and the counter frequency at which the counter increments (f counter ). For example, according to the following equation:

[0083]

[0084] As described herein, the fall time 668 associated with the voltage drop 665 can vary based on the resistance value of the conductive portion of the resistance-based sensing device. Thus, the fall time 668 can be used to determine the variable resistance (R var For example, the power dissipated by the conductive portion of a resistance-based sensing device having a variable resistance (P R ) can be determined by the following equation:

[0085]

[0086] Among them, P R is the dissipated power, E available is the energy that can be obtained from the energy storage device, t fall is the fall time 668. At the maximum voltage 662 (V H ) and minimum voltage 664(V L ) is constant, the energy (E available ) is also constant. For example, in the case where the energy storage device is a capacitor, the energy that can be obtained from the storage device can be determined by the following equation:

[0087]

[0088] Among them C storage is the capacitance of the capacitor used as a storage device. Therefore, in the case where available energy is dissipated through the conductive portion of the resistance-based sensing device, the power dissipated through the conductive portion of the resistance-based sensing device can be determined by the following equation:

[0089]

[0090] Furthermore, the power dissipated by the conductive portion of the resistance-based sensing device (P R ) and the variable resistance (R var ) are related by the following equation:

[0091] P R =I·V

[0092] where V is the average voltage dissipated through the conductive portion of the resistance-based sensing device, defined by the following equation:

[0093]

[0094] I is the average current through the resistor-based sensing device and is defined by the following equation:

[0095]

[0096] Therefore, the power dissipated by the conductive portion of the resistance-based sensing device (P R )for:

[0097]

[0098] As shown in the above equation, the variable resistance (R var ) and the corresponding physical characteristics of the surrounding environment can be determined based on the fall time 668 determined by the low-power timer using the power supply voltage detector to monitor the storage voltage 630 of the energy storage device. The determination of the variable resistance of the conductive portion of the resistance-based sensing device according to the process described herein is primarily based on the count value returned by the low-power timer. The count value is a digital value that can be represented by a discrete value. Therefore, when determining the count value and the variable resistance, an analog measurement of the variable resistance of the conductive portion of the resistance-based sensing device is not required. In contrast, in the previous examples, a voltage divider, a Wheatstone bridge, or other analog components are used to determine the variable resistance of the conductive portion of the resistance-based sensing device, which requires conversion from an analog value to a digital value.

[0099] Determining the variable resistance of the conductive portion of a resistance-based sensing device based on a digital count value and an interval time can eliminate the need for analog-to-digital converters and other power-consuming electrical components. Therefore, a low-energy resistance-based sensing system can run on a small amount of energy collected by an energy harvester and stored in an energy storage device (such as a capacitor), thereby eliminating the need for a battery. Eliminating batteries and ADCs in a low-energy resistance-based sensing system can significantly reduce the size and area of ​​the low-energy resistance-based sensing system and improve its stability and life expectancy. Reducing the size of the low-energy resistance-based sensing system and improving its stability can enable the low-energy resistance-based sensing system to be deployed in large quantities in areas that may be difficult to access.

[0100] Now refer to Figure 7 , depicts an example graph 770a depicting a storage voltage 730 in an energy storage device (e.g., energy storage device 106, storage capacitors 306, 406) versus time 766 during a plurality of energy harvesting states 761 and an active state 763. Also depicted is an example graph 770b depicting variable resistances 772a-772b determined based on fall times 768a-768c of the storage voltage 730.

[0101] like Figure 7 As shown, an exemplary low-energy resistance-based sensing system (e.g., low-energy resistance-based sensing system 100, 300, 400) continuously transitions between an energy harvesting state 761 and an active state 763. In the energy harvesting state 761, a controller (e.g., controller 102, 202, 302, 402) reduces power consumption, for example, by disabling power-consuming electronic components. In some embodiments, the low-energy resistance-based sensing system can enable a low-power timer (e.g., low-power timer circuitry 224, 324, 424) and a supply voltage detector (e.g., supply voltage detector circuitry 222, 322, 422) to monitor the voltage during the energy harvesting state 761. When the storage voltage 730 reaches or exceeds a predetermined maximum voltage 762, the low-energy resistance-based sensing system transitions to the active state 763. Similarly, when the storage voltage 730 is equal to or lower than a predetermined minimum voltage 764, the low-energy resistance-based sensing system transitions to the energy harvesting state 761.

[0102] The low-energy resistance-based sensing system can perform one or more operations during the active state 763. For example, the low-energy resistance-based sensing system can utilize the available energy in the energy storage device to transfer data. In addition, the low-energy resistance-based sensing system can utilize the available energy to recalibrate, for example, by transferring stored energy from the energy storage device to a reference resistor (e.g., reference resistor 110, 310, 410). The low-energy resistance-based sensing system can use a reference time interval corresponding to a reference voltage drop across the reference resistor to calibrate or recalibrate any model for determining the variable resistance 772 based on a time interval. The low-energy resistance-based sensing system can also utilize the available energy to measure the variable resistance 772 of the conductive portion of the resistance-based sensing device. As described herein, the low-energy resistance-based sensing system can determine the variable resistance 772 based at least in part on a time interval (e.g., fall time 768a, 768b, 768c) associated with the voltage drop 765 during the active state 763, in which the stored energy of the energy storage device is transferred through the resistance-based sensing device. In some embodiments, the low-energy resistance-based sensing system can alternate which tasks are performed during the active state 763. For example, the low-energy resistance-based sensing system can alternate between measuring the variable resistance 772 of the resistance-based sensing device and transmitting data related to the variable resistance 772 using the transceiver radio circuitry (e.g., the transceiver radio circuitry 220, 320, 420). In some embodiments, the low-energy resistance-based sensing system can perform multiple tasks during the active state 763. For example, measuring the variable resistance 772 of the resistance-based sensing device and transmitting data during the same active state 763.

[0103] like Figure 7 As further shown, the determined variable resistance 772 of the resistance-based sensing device can vary proportionally based on the fall times 768a-768c. For example, the variable resistance 772 of a resistance-based sensing device having a shorter fall time 768 can be smaller than the variable resistance 772 of a resistance-based sensing device having a longer fall time 768. Figure 7 As shown, the measured fall time 768a may correspond to the variable resistance 772a. However, the subsequently measured fall time 768b may be longer than the fall time 768a and thus correspond to a larger variable resistance 772b. The determination of the variable resistance of the resistance-based sensing device will be related to the Figure 6 Further description.

[0104] Now refer to Figure 8, an example process 880 is provided for determining a variable resistance (e.g., variable resistance 772) of a conductive portion of a resistance-based sensing device (e.g., resistance-based sensing device 108, 308, 408, 508). At block 882, a controller (e.g., controller 102, 202, 302, 402) transfers stored energy from an energy storage device (e.g., energy storage device 106, storage capacitor 306, 406) to the conductive portion of the resistance-based sensing device. The controller is configured to direct the stored energy of the energy storage device to the resistance-based sensing device. For example, the controller can be electrically connected to the energy storage device and the resistance-based sensing device such that the controller can directly provide a selectively enabled conductive path between the energy storage device and the resistance-based sensing device. In some embodiments, the controller can access a switch that provides a selectively enabled conductive path between the energy storage device and the resistance-based sensing device. In such embodiments, the controller can activate the switch during an active state and deactivate the switch during an energy harvesting state.

[0105] At block 884, the controller determines a time interval associated with a voltage drop in the energy storage device. When the controller measures a predetermined maximum voltage (e.g., maximum voltage 662, 762), the low-energy resistance-based sensing system enters an active state. Furthermore, when the controller creates a conductive path between the energy storage device and the resistance-based sensing device, a storage voltage associated with the energy storage device (e.g., storage voltage 330, 430, 630, 730) begins to decrease. The controller may initiate a low-power timer (e.g., low-power timer circuitry 224, 324, 424) to generate a count value based on the controller's clock frequency. The controller may also utilize a supply voltage detector (e.g., supply voltage detector circuitry 222, 322, 422) to monitor the storage voltage at the energy storage device during the active state. When the storage voltage is equal to or below a predetermined minimum voltage (e.g., minimum voltage 664, 764), the low-power timer count value may be recorded, and the low-energy resistance-based sensing system transitions back to the energy harvesting state. The recorded count value can be used to determine a time interval associated with the voltage drop from the maximum voltage to the minimum voltage.The time interval can be determined based on the count value, the clock frequency of the controller and / or the count frequency of the low power timer.

[0106] At block 886, the controller determines a variable resistance of the conductive portion of the resistance-based sensing device based at least in part on the time interval. Figure 6As described, the variable resistance of the conductive portion of the resistance-based sensing element can be determined based on a time interval associated with a voltage drop at the energy storage device. Utilizing a low-power timer to determine a count value associated with the voltage drop enables a digital measurement of the variable resistance of the conductive portion of the resistance-based sensing device to be determined without using a power-consuming analog-to-digital converter. The resistance of the conductive portion of the resistance-based sensing device is also related to the physical properties of the surrounding environment. Therefore, certain physical properties of the surrounding environment can be measured using a low-energy resistance-based sensing system without a battery. Such improvements enable the deployment of low-energy resistance-based sensing systems in difficult-to-access locations. Furthermore, the low or no maintenance requirements enable the deployment of a large number of low-energy resistance-based sensing systems without prohibitive maintenance requirements.

[0107] Although this detailed description sets forth some embodiments of the invention, the appended claims cover other embodiments of the invention that differ from the above-described embodiments according to various modifications and improvements. For example, those skilled in the art will recognize that such principles can be applied to any device that utilizes a resistance-based sensing device to determine the physical characteristics of the environment. For example, multiple smart bolts, nuts and / or washers deployed on a bridge, high-rise building, ship hull, roller coaster or other difficult-to-access location. Each individual smart bolt / nut / washer can be monitored over an extended period of time using a low-energy resistance-based sensing system according to the present disclosure without the need for limited maintenance. Changes in the pressure measured by the resistance-based sensing device can be detected, which can indicate a loose bolt. Faulty equipment can be addressed before a catastrophic failure occurs.

[0108] In the following claims, unless the specific terms "means for" or "step for" are used in a given claim, it is not intended that the claim be interpreted under 35 U.S.C. § 112, paragraph 6.

[0109] The use of broader terms such as "comprises," "includes," and "having" should be understood to support narrower terms such as "consisting of," "consisting essentially of," and "consisting essentially of. The use of the terms "optionally," "may," "might," "possibly," and the like with respect to any element of an embodiment means that the element is not required, or, alternatively, the element is required, both alternatives being within the scope of the embodiment(s). Furthermore, reference to examples is for illustrative purposes only and is not intended to be exclusive.

Claims

1. A device comprising: a resistance-based sensing device comprising a conductive portion configured to indicate a physical characteristic of an environment based on a variable resistance of the conductive portion; as well as a controller electrically coupled to the resistance-based sensing device, comprising one or more processors and one or more memory devices storing instructions that, when executed by the one or more processors, are operable to cause the one or more processors to: transferring stored energy from an energy storage device to the conductive portion of the resistance-based sensing device; determining a time interval associated with a voltage drop in the energy storage device; as well as The variable resistance of the conductive portion of the resistance-based sensing device is determined based at least in part on the time interval. 2 . The apparatus of claim 1 , further comprising an energy harvester configured to generate harvested energy and transmit the harvested energy to the energy storage device.

3. The apparatus of claim 2, wherein the energy harvester generates the harvested energy from a natural power source.

4. The device of claim 3, wherein the natural power source is at least one of solar energy, thermal energy, wind energy, and vibration energy. 5 . The apparatus of claim 1 , wherein the physical property indicated by the resistance-based sensing device is at least one of pressure, stress, temperature, and light. 6 . The apparatus of claim 1 , further comprising a low power timer electrically coupled to the controller and configured to generate a count value based on a clock frequency of the controller. The apparatus according to claim 6 , wherein the time interval is determined based on the count value. 8 . The apparatus of claim 1 , further comprising a power supply voltage detector electrically coupled to the controller and configured to determine a voltage value in the energy storage device. 9 . The apparatus of claim 8 , wherein the voltage drop corresponds to a difference between a first voltage value and a second voltage value determined by the supply voltage detector.

10. The apparatus of claim 9, wherein the second voltage value is associated with a minimum operating voltage of the controller.

11. The apparatus of claim 1 , further comprising a reference resistor having a known resistance value.

12. The apparatus of claim 11 , wherein the variable resistance of the conductive portion of the resistance-based sensing device is determined based at least in part on a reference time interval associated with a reference voltage drop in the energy storage device when the stored energy from the energy storage device is transferred to the reference resistor.

13. The apparatus of claim 1, further comprising a transceiver radio electrically coupled to the controller.

14. The apparatus of claim 13, wherein the time interval is transmitted by the transceiver radio, the time interval representing the variable resistance of the conductive portion of the resistance-based sensing device.

15. The apparatus of claim 1, wherein the variable resistance of the conductive portion of the resistance-based sensing device is determined without the use of an analog-to-digital converter.

16. A computer-implemented method for determining a variable resistance of a conductive portion of a resistance-based sensing device, the computer-implemented method comprising: transferring stored energy from an energy storage device to the conductive portion of the resistance-based sensing device via a controller; determining a time interval associated with a voltage drop in the energy storage device; as well as The variable resistance of the conductive portion of the resistance-based sensing device is determined based at least in part on the time interval.

17. The computer-implemented method of claim 16, further comprising: A count value is determined based on a low power timer electrically coupled to the controller and configured to increment the count value based on a clock frequency of the controller, wherein the time interval is determined based on the count value.

18. The computer-implemented method of claim 16, further comprising a power supply voltage detector electrically coupled to the controller and configured to determine a voltage value in the energy storage device.

19. The computer-implemented method of claim 18, further comprising: determining a first voltage value and a second voltage value by the power supply voltage detector, wherein the voltage drop corresponds to a difference between the first voltage value and the second voltage value, and The second voltage value is associated with the minimum operating voltage of the controller.

20. A computer program product for determining a variable resistance of a conductive portion of a resistance-based sensing device, the computer program product comprising at least one non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions including an executable portion configured to: transferring stored energy from an energy storage device to the conductive portion of the resistance-based sensing device via a controller; determining a count value based on a low power timer, the low power timer being electrically coupled to the controller and configured to increment the count value based on a clock frequency of the controller; determining a time interval associated with a voltage drop in the energy storage device based at least in part on the count value; as well as The variable resistance of the conductive portion of the resistance-based sensing device is determined based at least in part on the time interval.

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