WO2025126204A1 - A dendrometer, and a method of using thereof - Google Patents

Abstract

Embodiments of a dendrometer and a method of using thereof may include obtaining an oscillatoiy circuit that may include (a) a Variable Inductive Element (VIE) having an adjustable length, and (b) a capacitive device (e.g., a capacitor), connected to the VIE, and attaching the VIE to an object of interest. Inductance of the VIE may vary based on its length, and hence also based on geometry of the object. Embodiments may include connecting the oscillatory circuit to a power supply to generate an oscillatory signal, indicating diameter of the object. A processor may receive a count of oscillations of the oscillatory signal over a predetermined time interval, and thereby calculate a frequency of the oscillatory signal. The processor may subsequently determine the diameter of the object as a function of the calculated frequency.

Description

A DENDROMETER, AND A METHOD OF USING THEREOF

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application is a PCT International Application claiming the benefit of priority of U.S. Patent Application No. 63/608,307, filed December 11, 2023, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[002] The present invention relates generally to the field of measurement devices. More specifically, the present invention relates to a dendrometer, and a method of using thereof.

BACKGROUND OF THE INVENTION

[003] Dendrometers are devices adapted to measure diameter of physical objects. They find applications in various fields, such as industrial and agricultural applications.

[004] For example, dendrometers may be used for monitoring pipeline integrity, and detecting swelling that may indicate potential malfunctions. In plant sciences and agriculture, dendrometers may track plant growth, health, and water status, providing valuable data for research and crop management.

[005] Dendrometers are designed for a wide range of diameters, typically ranging from several centimeters to approximately 1 meter, with varying levels of accuracy, usually down to several hundreds of parts-per-million (ppm) of the measured quantity.

[006] Achieving accurate and reliable diameter measurements presents several challenges.

[007] Traditional dendrometers often rely on linear variable differential transducers (LVDT s), which are bulky and expensive. As elaborated herein, LVDT-based sensors require complex signal conditioning circuitry to handle fabrication offsets, extract phase and amplitude information, and convert the analog output to a digitized reading.

[008] Additionally, LVDTs are not lightweight, and their cost is influenced by their iron and magnet material content These factors limit the suitability of LVDT-based dendrometers for large sensor network applications, and miniaturized use-cases.

[009] Other currently available dendrometers may be based on strain-gauge sensors. As known in the art, such strain-gauge sensors are essentially produced as variable -length resistors, and exhibit the same deficiencies of weight, size and price as their LVDT-based counterparts. [0010] There is thus a need for a dendrometer that overcomes the limitations of traditional (e.g., LVDT based, strain-gauge based) devices, by offering a simple, cost-effective, and miniature solution. Such a dendrometer should provide accurate and reliable diameter measurements while being suitable for large-scale sensor networks and applications that require compact, and lightweight devices.

SUMMARY OF THE INVENTION

[0011] Embodiments of the invention may include a method of measuring a diameter of an object under test by at least one processor. Embodiments of the method may include obtaining an oscillatory circuit that may include (a) a Variable Inductive Element (VIE) having an adjustable length, and (b) a capacitive device (e.g., a capacitor), connected to the VIE.

[0012] Embodiments of the invention may further include attaching the VIE to an object under test. As explained herein, inductance of the VIE may vary based on its length, and hence also vary in response to change in geometiy (e.g., length, diameter, cross-section) of the attached object under test 20.

[0013] Embodiments of the invention may include connecting the oscillatory circuit to a power supply such as a battery or a photodetector, thereby configuring the oscillatory circuit to generate an oscillatory signal, as an indication of the diameter of the object under test.

[0014] According to some embodiments, at least one processor may receive, from a digital counter, a count of oscillations of the oscillatory signal over a predetermined time interval.

[0015] As explained herein, the at least one processor may calculate a frequency of the oscillatory signal based on the counted oscillations, and subsequently determine the diameter of the object of interest based on (e.g., as a function of) the calculated frequency.

[0016] Embodiments of the invention may include a dendrometer, or a length detector.

[0017] The dendrometer may include a VIE, having an adjustable length, and an inductance that varies according to that length. The dendrometer may further include at least one complementary circuit connected to the VIE, thereby forming an oscillatory circuit. The oscillatory circuit may be configured to, when connected to a power (e.g., voltage) supply, generate a first oscillatory signal at a first frequency, indicative of the length of the VIE. For example, the at least one complementary circuit may include a capacitor, and the first frequency may thereby be defined by capacitance of the capacitor and inductance of the VIE. [0018] In some embodiments, the VIE may be adapted to encircle a perimeter of an object under test, such that the first frequency may be indicative of said perimeter.

[0019] According to some embodiments, the at least one complementary circuit may further include an energy-restoring element (e.g., an active electrical component such as an operational amplifier, having positive feedback) that may be adapted to sustain the first oscillatory signal. [0020] Additionally, or alternatively, the at least one complementary circuit may include a digital counter, configured to count oscillations of the first oscillatory signal over a predetermined interval; and a microcontroller unit (MCU). The MCU may be configured to (i) calculate the first frequency based on the counted oscillations; and (ii) determine the length based on the first frequency.

[0021] Additionally, or alternatively, the at least one complementary circuit may include (i) a reference inductor; and (ii) a switch, adapted to switch between the reference inductor and the VIE. The MCU may be further adapted to control the switch, so as to generate a second oscillatory signal by the oscillatory circuit, using the reference inductor. The MCU may then calculate a second, reference frequency, based on counted oscillations of the second oscillatory signal. Based on the second frequency, The MCU may calculate a compensation value, and determine the length of the VIE (and hence - the object of interest) further based on the compensation value.

[0022] Additionally, or alternatively, the at least one complementary circuit may include a thermal sensor. The MCU may be further adapted to obtain a temperature reading from the thermal sensor. Based on the temperature reading, the MCU may calculate a thermal compensation value, and determine the length further based on the thermal compensation value, as further elaborated herein.

[0023] According to some embodiments, the VIE may include a conductive ring, adapted to encircle at least a portion of the object under test; and a stretchable spring, serially connected to the conductive ring. In such embodiments, inductance of the stretchable spring may vary as a function of its length.

[0024] Additionally, or alternatively, the VIE may include a conductive ring, adapted to encircle at least a portion of the object under test, and a sliding contact adjoint with the conductive ring. In such embodiments, the sliding contact may be adapted to slide along the conductive ring according to the length or perimeter of the object under test. The sliding contact may sustain electrical continuity with varying conducting length, thereby altering inductance of the VIE according to the length of the object of interest (also referred to herein as an “object under test”).

[0025] Additionally, or alternatively, the VIE may include a grid-pattern conductor. The gridpattern conductor may be adapted to encircle at least a portion of the object under test; and stretch as a result of a change in perimeter of the object under test, thereby altering inductance of the VIE.

[0026] According to some embodiments, the at least one complementary circuit may further include a wireless communication module integrated with the MCU. The wireless communication module may be adapted to transmit the determined length of the object under test to a remote computing device, via a wireless (e.g., Wi-Fi, Bluetooth, Cellular, etc.) communication channel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0028] Fig. 1 is a block diagram, depicting a computing device which may be included in a dendrometer, according to some embodiments of the invention;

[0029] Fig. 2A is a schematic three dimensional (3D) diagram depicting a Linear Variable Differential Transducer (LVDT) - based dendrometer, as known in the art;

[0030] Fig. 2B is a schematic three dimensional (3D) diagram depicting application of a dendrometer for measuring a length (e.g., a diameter, a perimeter) of an object of interest (also denoted “object under test”), according to some embodiments of the invention;

[0031] Fig. 3 is a schematic block diagram, depicting components of a dendrometer, as a system for measuring a length (e.g., a diameter or perimeter) of an object of interest, according to some embodiments of the invention;

[0032] Fig. 4 is a schematic electric diagram, depicting components of the dendrometer (e.g., the same dendrometer as in Fig. 3), according to some embodiments of the invention; [0033] Figs. 5A, 5B and 5C show different configurations of Variable Inductive Elements (VIEs), that may be included in a dendrometer, according to some embodiments of the invention;

[0034] Fig. 6 is a schematic block diagram, depicting components of the dendrometer (e.g., the same dendrometer as in Fig. 3), during a process of calibration, according to some embodiments of the invention;

[0035] Fig 7 is a schematic electric drawing, showing an implementation of an all-electric dendrometer, according to some embodiments of the invention;

[0036] Fig. 8 is a graph showing results of length measurements by a dendrometer, according to some embodiments of the invention; and

[0037] Fig. 9 is a schematic flow diagram depicting steps in a method of measuring a length (e.g., diameter, perimeter) of an object under test by at least one processor, using the dendrometer, according to some embodiments of the invention.

[0038] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0039] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0040] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. Some features or elements described with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated.

[0041] Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, “processing,” “computing,” “calculating,” “determining,” “establishing”, “analyzing”, “checking”, or the like, may refer to operations) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and/or transforms data represented as physical (e.g., electronic) quantities within the computer’s registers and/or memories into other data similarly represented as physical quantities within the computer’s registers and/or memories or other information non-transitory storage medium that may store instructions to perform operations and/or processes.

[0042] Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. The term “set” when used herein may include one or more items.

[0043] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0044] Reference is now made to Fig. 1, which is a block diagram depicting a computing device, which may be included within an embodiment of a dendrometer, according to some embodiments.

[0045] Computing device 1 may include a processor or controller 2 that may be, for example, a central processing unit (CPU) processor, a chip or any suitable computing or computational device, an operating system 3, a memory 4, executable code 5, a storage system 6, input devices 7 and output devices 8. Processor 2 (or one or more controllers or processors, possibly across multiple units or devices) may be configured to cany out methods described herein, and/or to execute or act as the various modules, units, etc. More than one computing device 1 may be included in, and one or more computing devices 1 may act as the components of, a system according to embodiments of the invention. [0046] Operating system 3 may be or may include any code segment (e.g., one similar to executable code 5 described herein) designed and/or configured to perform tasks involving coordination, scheduling, arbitration, supervising, controlling or otherwise managing operation of computing device 1, for example, scheduling execution of software programs or tasks or enabling software programs or other modules or units to communicate. Operating system 3 may be a commercial operating system. It will be noted that an operating system 3 may be an optional component, e.g., in some embodiments, a system may include a computing device that does not require or include an operating system 3.

[0047] Memoiy 4 may be or may include, for example, a Random-Access Memory (RAM), a read only memory (ROM), a Dynamic RAM (DRAM), a Synchronous DRAM (SD-RAM), a double data rate (DDR) memory chip, a Flash memoiy, a volatile memoiy, a non-volatile memory, a cache memory, a buffer, a short term memory unit, a long term memoiy unit, or other suitable memoiy units or storage units. Memory 4 may be or may include a plurality of possibly different memory units. Memory 4 may be a computer or processor non-transitory readable medium, or a computer non-transitoiy storage medium, e.g., a RAM. In one embodiment, a non-transitory storage medium such as memory 4, a hard disk drive, another storage device, etc. may store instructions or code which when executed by a processor may cause the processor to carry out methods as described herein.

[0048] Executable code 5 may be any executable code, e.g., an application, a program, a process, task, or script. Executable code 5 may be executed by processor or controller 2 possibly under control of operating system 3. For example, executable code 5 may be an application that may measure a length (e.g., diameter, perimeter) of an object of interest, as further described herein. Although, for the sake of clarity, a single item of executable code 5 is shown in Fig. 1, a system according to some embodiments of the invention may include a plurality of executable code segments similar to executable code 5 that may be loaded into memory 4 and cause processor 2 to carry out methods described herein.

[0049] Storage system 6 may be or may include, for example, a flash memory as known in the art, a memory that is internal to, or embedded in, a micro controller or chip as known in the art, a hard disk drive, a CD-Recordable (CD-R) drive, a Blu-ray disk (BD), a universal serial bus (USB) device or other suitable removable and/or fixed storage unit. Data pertaining to physical measurements may be stored in storage system 6 and may be loaded from storage system 6 into memory 4 where it may be processed by processor or controller 2. In some embodiments, some of the components shown in Fig. 1 may be omitted. For example, memory 4 may be a nonvolatile memory having the storage capacity of storage system 6. Accordingly, although shown as a separate component, storage system 6 may be embedded or included in memory 4.

[0050] Input devices 7 may be or may include any suitable input devices, components, or systems, e.g., a detachable keyboard or keypad, a mouse and the like. Output devices 8 may include one or more (possibly detachable) displays or monitors, speakers and/or any other suitable output devices. Any applicable input/output (I/O) devices may be connected to Computing device 1 as shown by blocks 7 and 8. For example, a wired or wireless network interface card (NIC), a universal serial bus (USB) device or external hard drive may be included in input devices 7 and/or output devices 8. It will be recognized that any suitable number of input devices 7 and output device 8 may be operatively connected to Computing device 1 as shown by blocks 7 and 8.

[0051] A system according to some embodiments of the invention may include components such as, but not limited to, a plurality of central processing units (CPU) or any other suitable multi-purpose or specific processors or controllers (e.g., similar to element 2), a plurality of input units, a plurality of output units, a plurality of memory units, and a plurality of storage units.

[0052] Reference is made to Fig. 2A, which is a schematic 3D diagram depicting a Linear Variable Differential Transducer (LVDT) - based dendrometer, as known in the art.

[0053] Dendrometers are commonly composed of three parts: a mechanical sensing element, such as a band, having a single or a multi-point mount; a transducer that translates mechanical changes in diameter to electrical signals; and a processor, associated with a communication interface, for processing and relay the obtained measurements.

[0054] While there still exist purely mechanical dendrometers with physical dials that indicate the measured diameter, the vast majority of modem dendrometers operate LVDTs to convert the measured mechanical changes to electrical signals. Such LVDTs utilize a sliding magnetic core that induces a position-dependent flux linkage between a primary coil (A), and two secondary coils (B), as illustrated in Fig. 2A.

[0055] an AC signal at input A will result a differential, position-dependent voltage at output B. LVDTs are widely used in industry, and are robust and reliable. However, they require fairly complex signal conditioning circuitry to overcome fabrication offsets, extract the phase and amplitude information from the output AC signal, and convert the AC output to digitized reading. Furthermore magnetic cores and coils are not lightweight, and their cost is mainly set by the iron and magnet material content.

[0056] The processing and relay of dendrometer measured signals is usually done using a microcontroller unit (MCU) that is located adjacent the sensor. Such MCUs may include analog hardware such as operational amplifiers, comparators, and the like. However, the complexity of signal conditioning circuits required by LVDTs typically renders them prohibitively costly for integration into low-cost MCUs.

[0057] In other words, structural limitations of the physical sensor, transducer, and processing hardware in currently available dendrometers commonly incur high build costs, and inconvenient constraints on form-factor.

[0058] Therefore, LVDT-based dendrometers are not well suited for large sensor network applications, or for miniaturized use-cases.

[0059] Embodiments of the invention include a novel dendrometer that works on the principle of frequency shift. In contrast with currently available dendrometers, the dendrometer of the present invention may be all-electrical, e.g., devoid of an electro-mechanical transducer, and may easily interface a digital system to provide indication of a measured length (e.g., diameter, perimeter). As a result, the dendrometer of the present invention may easily interface a low- cost MCU or a miniature, low-cost custom integrated circuit (IC) such as an IC of an Internet of things (loT) device, and can accommodate requirements of mass-producible, low-cost dendrometers for sensor network applications.

[0060] Currently available dendrometers are typically used to measure a “diameter” of an object (e.g., a stem) of interest by clamping to two opposite sides of that object. In other words, currently available dendrometers may be referred to as “point dendrometers”, in a sense that they may measure a distance between two points. Some variants include dendrometers that measure a distance between 3 points, hence referred to as “multi-point” dendrometers. It may be appreciated that such available dendrometers may exhibit poor accuracy when mounted at unsuitable locations, e.g. where the object (e.g., stem) is scarred. In such conditions, the measured values may not represent an actual change in a diameter of the stem.

[0061] Embodiments of the invention may be adapted to measure an actual increase in a crosssection, of the object of interest 20. In other words, dendrometer 10 may capture an overall broadening of an object (e.g., a stem) 20 of interest, even in case of inhomogeneity. Dendrometer 10 may therefore be utilized for measuring changes in a cross-section of a measured object, and may not be subject to the limitations of single-point, and multiple-point dendrometers, as explained herein.

[0062] Embodiments of the invention may implement an oscillation circuit (also referred to herein as an “LC oscillator”, “LC oscillation circuit”, “LC tank circuit”, and the like) to sense changes in lengths of objects of interest 20. The term “length” may be used herein to refer to any geometrical size of interest, which may be measured by embodiments of the invention, such length may include, for example, a diameter of object 20, a radius of object 20, a complete perimeter of object 20, a partial perimeter of object 20, and the like.

[0063] An oscillator is a system that utilized feedback to sustain a periodic - current or voltage signal waveform. In an LC-oscillator, this waveform is sustained by incorporating an inductor and capacitor, which can exhibit oscillatory behavior with an energy-restoring mechanism.

[0064] The values of the inductor and the capacitor (denoted ‘L’ and ‘C’ respectively) define the frequency of the oscillation.

[0065] Embodiments of the invention may use a variable inductive element (VIE), as an indication of length change. This VIE may be implemented as an inductor with a cross-sectional dependent inductance L(a), where ‘a’ represents the cross-section being measured. When the length of the device under test (DUT) changes, L(a) also changes, resulting in a different frequency of oscillation.

[0066] The dendrometer of the present invention may translate the measured length quantity to a deviation from a quiescent oscillation frequency. A time-based digital counter may be used for measurement readout, thereby circumventing the need for analog-to-digital conversion (ADC) of the measured signal.

[0067] Fig. 2B is a schematic 3D diagram depicting application of a dendrometer for measuring a length (e.g., a diameter, a perimeter) of an object under test, according to some embodiments of the invention. As shown in Fig. 2B, a dendrometer of the present invention may use a frequency shift sensor to detect variations in a cross-section of an object (e.g., a cylindrical object) by encircling a VIE around it.

[0068] As explained herein, leads of the VIE may be connected in parallel to a capacitor, and to an energy-restoring element (or a “negative resistor”, as commonly referred to in the art). The VIE, capacitor and energy-restoring element may thereby form an LC-oscillation circuit that may sustain an oscillatory voltage signal across the capacitor, when connected to a power supply. Oscillations (e.g., zero-crossings) of the oscillatory voltage signal may be periodically counted by a digital counter, and may be recorded over a known timing interval (or “timing gate” as also referred to herein), to produce a frequency reading.

[0069] A change (A) in the VIE inductance L(a) may result in a change in the frequency of oscillation (o_OSc, as elaborated in Eq. 1 below:

Eq. 1

where ‘C’ represents the capacitance of the oscillatory circuit, and Lo represents a nominal value of inductance of the VIE, at a predetermined nominal length.

[0070] As seen in Eq. 1, a shift in measured frequency may relate to inductance as an inverse square root. When the change in inductance (AL(a)) is small enough, the behavior of the dendrometer may be approximated as linear according to Eq. 2 below, facilitating an easier implementation.

where coo is a nominal natural oscillation frequency, at the predetermined nominal length.

[0071] It may be appreciated that when the change in length is small, the incurred, small change in inductance AL(a) may be presented as portions (e.g., parts per million - PPM) of the nominal inductance Lo, as shown herein (e.g., in relation to Fig. 8).

[0072] Reference is now made to Fig. 3, which is a schematic block diagram, depicting components of a dendrometer as a system 10 for measuring a length of an object of interest, according to some embodiments of the invention. The terms “dendrometer” and “system” may be used in this context interchangeably.

[0073] According to some embodiments of the invention, system 10 may be implemented as combination of software and hardware modules. For example, system 10 may include a microcontroller unit (MCU) 210 that may be implemented by a computing device such as element 1 of Fig. 1. Additionally, or alternatively, MCU 210 may be or may include a controller such as controller 2 of Fig. 1.

[0074] MCU 210 may be adapted to execute one or more modules of executable code (e.g., element 5 of Fig. 1) to obtain one or more physical measurements, and calculate a length of an object of interest 20 based on these physical measurements, as further described herein. [0075] As shown in Fig. 3, arrows may represent flow of one or more data elements to and from system 10 and/or among modules or elements of system 10. Some arrows have been omited in Fig. 3 for the purpose of clarity.

[0076] Reference is also made to Fig. 4, which is a schematic electric diagram, depicting components of the dendrometer 10 (e.g., the same dendrometer 10 as in Fig. 3), according to some embodiments of the invention.

[0077] As elaborated herein, system 10 may include a VIE 100 (e.g., same VIE 100 as in Fig. 2B), having an adjustable length. The inductance of VIE 100 may vary according to that adjustable length. For example, VIE 100 may be adapted to be atached to an object under test 20, such that inductance L(a) may correspond to the length of the object under test 20. Additionally, or alternatively, VIE 100 may be adapted to encircle the object under test as depicted in Fig. 2B, such that inductance L(a) may correspond to a length (e.g., diameter) of the object under test 20.

[0078] As shown in Figs. 3 and 4, system 10 may further include at least one complementary circuit 200 connected to VIE 100, thereby forming an oscillatory circuit 300. Oscillatory circuit 300 may be configured to produce an oscillatory signal 300 when connected to an electric power supply 290.

[0079] For example, at least one complementary circuit 200 may be, or may include a capacitive device 220 (e.g., capacitor ‘Cose’ of Fig. 4), adapted to be connected in parallel to VIE 100, so as to produce oscillatory circuit 300.

[0080] In another example, at least one complementary circuit 200 may be implemented as an Integrated Circuit (IC) or a chip. IC complementary circuit 200 may include at least one capacitive device 220 and/or inductive elements 222, and may be connected to VIE 100 in any combination of parallel and/or serial connections, to form oscillatory circuit 300.

[0081] In yet another example, at least one complementary circuit 200 may be further implemented as an assembly of a plurality of discrete components. Other combinations and configurations are also possible.

[0082] As the inductance L(a) of VIE 100 may be a function of a length of object under test 20, oscillatory circuit 300 may be configured to generate a first oscillatory signal 300S1 at a first frequency 210F (e.g., a “measurement frequency”, ®_0Sc of Eq. 1 and 2), that is indicative of that length. [0083] Additionally, or alternatively, when VIE 100 is adapted to encircle a perimeter of object under test 20, the measurement frequency 21 OF a>_Osc of oscillatory signal 300S1 may be indicative of that perimeter.

[0084] When complementary circuit 200 includes a capacitive device 220 (e.g., capacitor ‘C_0Sc’ of Fig. 4), measurement frequency 21 OF (ro₀sc) may be determined, or defined by capacitance of capacitive device 220 (C_osc) and inductance of VIE 100, as elaborated in Eq. 1.

[0085] According to some embodiments, at least one complementary circuit 200 may further include an energy-restoring element 250 (denoted “-g” in Fig. 4), adapted to sustain the first oscillatory signal.

[0086] For example, energy-restoring element 250 may be, or may include an active component, such as an operational amplifier (Op-Amp) having positive feedback, so as to maintain resonance of an oscillatory signal 300S 1 by oscillatory circuit 300 over time, as known in the art.

[0087] According to some embodiments, MCU 210 may be configured to calculate the measurement frequency 210F (ro_Osc) based on oscillatory signal 300S1.

[0088] For example, dendrometer 100 may include (e.g., in at least one complementary circuit 200) a digital counter 260 and a timer 270. Timer 270 may be configured to measure a predetermined interval (or “gate”, as denoted in Fig. 4). Counter 260 may be configured to count 260C oscillations (e.g., zero-crossings) of oscillatory signal 300S1 within that predetermined interval.

[0089] It may be appreciated that counter 260 may be adjoint with any required analog electrical components as required to identify, and count 260C individual oscillations (e.g., the zero-crossings), thereby obviating a need to include more expensive circuitry such as an analog- to-digital converter (ADC).

[0090] MCU 210 may subsequently calculate measurement frequency 21 OF (ro₀sc) based on the counted oscillations 260C within the gate interval. For example, MCU 210 may divide counted oscillations 260C by the gated interval of timer 270 to arrive at the measured frequency 21 OF value.

[0091] MCU 210 may then calculate an impedance (e.g., inductance) value 210LIMP of VIE 100 based on measurement frequency 21 OF, e.g., according to Eq. 1 or Eq. 2. [0092] MCU 210 may proceed to determine a length (e.g., diameter, perimeter, etc.) of the object of interest 20 based on calculated frequency 21 OF (e.g., based on inductance value 210LIMP of VIE 100).

[0093] For example, MCU 210 may use a look-up table (LUT) 210LUT to associate between specific lengths of VIE 100 and respective values of impedance (e.g., inductance) value 210LIMP, to arrive at a length 210LNG of VIE (and subsequently- of attached object 20), that corresponds with calculated measurement frequency 21 OF.

[0094] Additionally, or alternatively, MCU 210 may calculate length 210LNG of VIE (and of object 20) as a function, or relation of 210LIMP. For example, MCU 210 may calculate length 210LNG according to a linear function of 210LIMP, as shown herein (e.g., in relation to Fig. 8).

[0095] Reference is now made to Figs. 5A, 5B and 5C, which show different, non-limiting examples for configurations of Variable Inductive Elements (VIEs), that may be included in a dendrometer 10, according to some embodiments of the invention.

[0096] It may be appreciated that a gain of dendrometer 100 may depend on specific physical implementation of VIE 100. Three exemplary VIEs are presented in Figs. 5A-5C. These include a conductive ring with a stretchable spring in series (Fig. 5A), a conductive ring with a sliding contact that sustains electrical continuity with varying conductor length (Fig. 5B), and a gridpattern conductor, adapted to stretch as a result in a change in the diameter of the object of interest (Fig. 5C).

[0097] According to some embodiments, VIE 100 may include a conductive ring 110, adapted to encircle at least a portion of the object under test 20 (e.g., as shown in Fig. 2B), and a stretchable spring 120 (e.g., as shown in Fig. 5A), which may be serially connected to the conductive ring 110. Additionally, or alternatively, VIE 100 may include only the stretchable spring 120 of Fig. 5A (e.g., without an additional conductive ring element 110 connected in series to the stretchable spring 120). Other such combinations are also available.

[0098] According to some embodiments, inductance of the stretchable spring 120 may vary as a function of its length and/or shape of its coils, thereby changing the inductance of VIE 100, and the subsequent, measured oscillatory frequency 21 OF.

[0099] Additionally, or alternatively, VIE 100 may include a conductive ring 110, adapted to encircle at least a portion of the object under test 20 (e.g., as shown in Fig. 2B), and a sliding contact element 130 (e.g., as shown in Fig. 5B), which may be serially connected to the conductive ring 110. Sliding contact element 130 may be adapted to slide along the conductive ring 110 according to a size or length of object under test 20, and sustain electrical continuity with vaiying conducting length. Sliding contact element 130 may thereby alter inductance of VIE 100, and may subsequently change measured oscillatory frequency 21 OF as a function of geometry and size of the object under test 20.

[00100] Additionally, or alternatively, VIE 100 may include a grid-pattern conductor 140, adapted to encircle at least a portion of length of the object under test 20. For example, gridpattern conductor 140 may be adapted to encircle an entire length (e.g., an entire perimeter) of object under test 20. Additionally, or alternatively may be serially connected to at least one conductive ring element 110, and may be adapted to encircle the perimeter of the object under test 20, in conjunction with conductive ring element 110. Grid-pattern conductor 140 may be configured to stretch as a result of a change in length (e.g., perimeter) of the object under test 20, thereby altering its inductance.

[00101] For example, the inventors have experimentally tested a grid-pattern conductor 140 having 10 segments, where W2=0 (e.g., using a triangular pattern). When W1 = H = 3cm, the measured nominal inductance of VIE 100 was approximately 300 nano-Henry (nH). When the VIE 100 was stretched to its maximal length, H approached 0, and W1 approached 4.25cm. In this configuration, the inductance of VIE 100 rose to approximately 450nH.

[00102] Grid-patern conductor 140 may thereby alter inductance of VIE 100, and may subsequently change measured oscillatory frequency 21 OF as a function of geometry and size of the object under test 20.

[00103] Reference is made to Fig. 6, which is a schematic block diagram, depicting components of the dendrometer (e.g., the same dendrometer as in Fig. 3), during a process of calibration, according to some embodiments of the invention.

[00104] The inventors have experimentally observed sensitivity of oscillatoiy circuit 300SI to ambient conditions such as temperature drifts, which affect the capacitance of capacitive device (e.g., capacitor) 220, thereby changing frequency 21 OF of oscillatory signal 300S1 independently of VIE 100.

[00105] As shown in Fig. 6, the at least one complementary circuit 200 of dendrometer 100 may include a fixed reference inductor 240, and at least one switch 230. The at least one switch 230 may be adapted to switch between reference inductor 240 and VIE 100 in oscillatory circuit 300. [00106] In other words, as shown in Fig. 6, reference inductor 240 may replace VIE 100 in oscillatory circuit 300, for purposes of calibration and drift-cancellation.

[00107] According to some embodiments, reference inductor 240 may be, or may include a fixed inductor with an air core, as such inductors were found to be hardly affected by such ambient conditions, and thereby appropriate in the capacity of calibrating dendrometer 100.

[00108] According to some embodiments, in a calibration mode of operation, MCU 210 may control the at least one switch 230 to use reference inductor 240, so as to generate a second oscillatory signal 300S2 by the oscillatory circuit.

[00109] MCU 210 may then utilize counter 260 and timer 270 as elaborated herein (and will not be repeated for the purpose of brevity), to calculate a second, frequency 210F’ (referred to herein as a “reference” frequency), based on counted oscillations of the second oscillatory signal 300S2.

[00110] Based on the second frequency 21 OF ’ , MCU 210 may then calculate a compensation value 210CMP. Compensation value 210CMP may indicate a change in capacitance of capacitive element (e.g., capacitor) 220. Additionally or alternatively, compensation value 210CMP may indicate a change in frequency 210F due to the applied ambient temperature.

[00111] MCU 210 may subsequently recalculate frequency 21 OF based on compensation value 210CMP, to arrive at a calibrated, or amended value of inductance 210LIND’ of VIE 100. MCU 210 may proceed to determine the length 210LEN as elaborated herein (e.g., in relation to Fig. 3), using the amended value of inductance 210LIND’, to arrive at an amended value 210LNG’ of VIE 100 (and subsequently - of attached object 20).

[00112] Additionally, or alternatively, the at least one complementary circuit 200 of dendrometer 100 may include a thermal sensor 290. MCU 210 may be adapted to obtain a temperature reading 290TMP from thermal sensor 290, and may determine length 210LNG’ further based on temperature reading 290TMP.

[00113] For example, MCU 210 may calculate a thermal compensation value 210TCMP based on the temperature reading. Thermal compensation value 210TCMP may, for example, reside in LUT 210LUT, and may associate between a specific value of temperature reading 290TMP and a respective, required compensation 210LNG’ in estimated length 210LNG of VIE 100. MCU 210 may subsequently calculate an amended value of length 210LNG’ of VIE 100, based on the thermal compensation value 210TCMP. [00114] Additionally, or alternatively, thermal compensation value 21 OTCMP may represent a required amendment 21 OLIND’ to calculated an amended value of induction 21 OLIND. MCU 210 may subsequently calculate an amended value 210L1ND’ of VIE 100 induction value 21 OLIND based on thermal compensation value 21 OTCMP, and then proceed to calculate an amended value of length 210LNG’ of VIE 100, based on the amended value of induction 210LIND (e.g., via LUT 210LUT, as explained herein).

[00115] Fig. 7 is a schematic electric drawing, showing a non-limiting example for implementation of an all-electric dendrometer 10, according to some embodiments of the invention. Dendrometer 10 of Fig. 7 may be the same as dendrometer 10 of Figs. 3, 4 and 6.

[00116] As shown in Fig. 7, dendrometer 10 may include an oscillatory circuit, adapted to interface VIE 100, and produce oscillatory signal(s) 300S1, 300S2.

[00117] Additionally, or alternatively, dendrometer 10 may include one or more complementary circuits 200. Complementary circuits 200 may include: a power supply and filtering circuit, an energy restoring circuit, a timer circuit, and a counter circuit (or a buffer for interfacing an external counter circuit).

[00118] Additionally, or alternatively, at least one complementary circuit 200 of dendrometer 10 may include a communication module or interface (wireless communication module) 280 that may be integrated with, or in collaboration with MCU 210. Communication module 280 may, for example, include a wireless transceiver such as a Wi-Fi transceiver or an Internet of Things (loT) transceiver, and may be adapted to transmit the determined length 210LNG of the object under test 20 to a remote computing device 50 such as computing device 1 of Fig. 1.

[00119] For example, remote computing device 50 may include a server computer, adapted to monitor or manage measurements of a plurality of objects of interest, by a respective plurality of dendrometers 10 of the present invention.

[00120] Fig. 8 is a graph showing results of length experimentally-obtained measurements of a length of an object of interest 20 by a dendrometer, according to some embodiments of the invention. The X-axis of Fig. 8 represents variation of difference (or a “gap”) between different conducted measurements. The X-axis of Fig. 8 represents variation of measurement results of length 210LNG, presented parts-per-million (ppm) for a nominal, initial value.

[00121] The obtained results were repetitive to a high degree, and have exhibited a linear relation between the actual length (diameter) of object 20 and the calculated measurement values 210LNG. Moreover, embodiments of the invention have exhibited excellent accuracy, as manifested by a calculated R² value of 0.9993.

[00122] Fig. 9 is a schematic flow diagram depicting steps in a method of measuring a length (e.g., diameter) of an object under test by at least one processor (e.g., processor 2 of Fig. 1), using the dendrometer (e.g., same as dendrometer 10 of previous figures), according to some embodiments of the invention.

[00123] As shown in step S1005, embodiments of the invention may include obtaining an oscillatory circuit (e.g., oscillatory circuit 300 of Fig. 3). As elaborated herein, oscillatory circuit 300 may include (a) a VIE (e.g., VIE 100 of any of the previous figures) having an adjustable length, and (b) a capacitive device (e.g., element 220 of Fig. 3, such as a capacitor), connected to VIE 100.

[00124] As shown in step SI 010, embodiments of the invention may include attaching VIE 100 to an object under test 20. As explained herein, inductance of VIE 100 may vary based on its length, and hence also vary in response to change in geometry (e.g., length, diameter, crosssection) of the attached object under test 20.

[00125] As shown in step S1015, embodiments of the invention may include connecting the oscillatory circuit to a power supply (e.g., 290 of Fig. 3) such as a battery, thereby configuring the oscillatory circuit to generate the oscillatory signal, as an indication of the diameter of the object under test.

[00126] As shown in step S1020, the at least one processor 2 (e.g., MCU 210 of Fig. 3) may receive, from a digital counter (e.g., 260 of Fig. 3), a count of oscillations of the oscillatory signal 300S1 over a predetermined time interval (e.g., gated by timer 270 of Fig. 3).

[00127] As shown in steps S1025 and S1030, the at least one processor 2 (e.g., MCU 210) may calculate a frequency of the oscillatory signal based on the counted oscillations, and subsequently determine the diameter of the object of interest based on the calculated frequency as elaborated herein.

[00128] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Furthermore, all formulas described herein are intended as examples only and other or different formulas may be used. Additionally, some of the described method embodiments or elements thereof may occur or be performed at the same point in time. [00129] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[00130] Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.

Claims

1. A dendrometer, comprising: a Variable Inductive Element (VIE), having an adjustable length, and an inductance that varies according to that length; and at least one complementary circuit connected to the VIE, thereby forming an oscillatory circuit, wherein the oscillatory circuit is configured to generate a first oscillatory signal at a first frequency, indicative of said length.

2. The dendrometer of claim 1, wherein the VIE is adapted to encircle a perimeter of an object under test, such that the first frequency is indicative of said perimeter.

3. The dendrometer according to any one of claims 1-2, wherein the at least one complementary circuit comprises a capacitor, and wherein the first frequency is defined by capacitance of the capacitor and inductance of the VIE.

4. The dendrometer of claim 3, wherein the at least one complementary circuit further comprises an energy-restoring element, adapted to sustain the first oscillatory signal.

5. The dendrometer according to any one of claims 3-4, wherein the at least one complementary circuit further comprises: a digital counter, configured to count oscillations of the first oscillatory signal over a predetermined interval; and a microcontroller unit (MCU), configured to (i) calculate the first frequency based on the counted oscillations; and (ii) determine the length based on the first frequency.

6. The dendrometer of claim 5, wherein the at least one complementary circuit further comprises: a reference inductor; and a switch, adapted to switch between the reference inductor and the VIE.

7. The dendrometer of claim 6, wherein the MCU is further adapted to: control the switch, so as to generate a second oscillatory signal by the oscillatory circuit, using the reference inductor; calculate a second, reference frequency, based on counted oscillations of the second oscillatory signal; based on the second frequency, calculate a compensation value; and determine the length further based on the compensation value.

8. The dendrometer according to any one of claims 5-7, wherein the at least one complementary circuit further comprises a thermal sensor, and wherein the MCU is further adapted to: obtain a temperature reading from the thermal sensor; based on the temperature reading, calculate a thermal compensation value; and determine the length further based on the thermal compensation value.

9. The dendrometer according to any one of claims 2-8, wherein the VIE comprises: a conductive ring, adapted to encircle at least a portion of the object under test; and a stretchable spring, serially connected to the conductive ring, wherein inductance of the stretchable spring varies as a function of its length.

10. The dendrometer according to any one of claims 2-9, wherein the VIE comprises a conductive ring, adapted to encircle at least a portion of the object under test, and a sliding contact adapted to: slide along the conductive ring according to the perimeter of the object under test; and sustain electrical continuity with varying conducting length, thereby altering inductance of the VIE.

11. The dendrometer according to any one of claims 2- 10, wherein the VIE comprises a gridpattern conductor, adapted to: encircle at least a portion of the object under test; and stretch as a result of a change in perimeter of the object under test, thereby altering inductance of the VIE.

12. The dendrometer according to any one of claims 5-11, wherein the at least one complementary circuit further comprises a wireless communication module integrated with the MCU, and wherein said wireless communication module is adapted to transmit the determined length of the object under test to a remote computing device.

13. A method of measuring a length of an object under test by at least one processor, the method comprising: receiving, from a digital counter, a count of oscillations of a first oscillatory signal over a predetermined time interval; calculating a first frequency of the first oscillatory signal based on the counted oscillations; and determining the length based on the calculated frequency.

14. The method of claim 13, further comprising: obtaining an oscillatory circuit, comprising (a) a Variable Inductive Element (VIE) having an adjustable length, wherein inductance of the VIE varies based on its length, and (b) a capacitor, connected to said VIE; attaching the VIE to the object under test; and connecting the oscillatory circuit to a power supply, thereby configuring the oscillatory circuit to generate the first oscillatory signal, as an indication of the diameter of the object under test.

15. The method of claim 14, wherein the VIE is adapted to encircle a perimeter of the object under test, such that the first frequency is indicative of said perimeter.

16. The method according to any one of claims 14-15 wherein the oscillatory circuit further comprises (a) a reference inductor, and (b) a switch, adapted to switch between the reference inductor and the VIE.

17. The method of claim 16, wherein the at least one processor is further adapted to: control the switch, so as to generate a second oscillatory signal by the oscillatory circuit, using the reference inductor; calculate a second, reference frequency, based on counted oscillations of the second oscillatory signal; based on the second frequency, calculate a compensation value; and determine the length further based on the compensation value.

18. The method according to any one of claims 14-17, wherein the at least one processor is further configured to: obtain a temperature reading from a thermal sensor; based on the temperature reading, calculate a thermal compensation value; and determine the length further based on the thermal compensation value.

19. The method according to any one of claims 14-18, wherein the VIE comprises: a conductive ring, adapted to encircle at least a portion of the object under test; and a stretchable spring, serially connected to the conductive ring, wherein inductance of the stretchable spring varies as a function of its length.

20. The method according to any one of claims 14-19, wherein the VIE comprises a conductive ring, adapted to encircle at least a portion of the object under test, and a sliding contact adapted to: slide along the conductive ring according to the perimeter of the object under test; and sustain electrical continuity with varying conducting length, thereby altering inductance of the VIE.

21. The method according to any one of claims 14-20, wherein the VIE comprises a gridpattern conductor, adapted to: encircle at least a portion of the object under test; and stretch as a result of a change in perimeter of the object under test, thereby altering inductance of the VIE.

22. The method according to any one of claims 14-21, wherein the at least one processor is further configured to transmit the determined length of the object under test to a remote computing device via a wireless communication channel.