Abstract:
A dendrometer comprises a dendrometer band whose length is extendable for encircling a tree trunk. The dendrometer further comprises an elongated electronic component that is closely or contiguously attached to the dendrometer band for moving along with the dendrometer band in order to follow length extension of the dendrometer band. Length variation of the dendrometer band is configured to be converted to electronic signals by the electronic component.

Description:
FIELD OF INVENTION 
       [0001]    The present application relates to a dendrometerfor measuring diameters or circumferences of tree branches or trunks. The application also relates to methods for making, assembling, installing, configuring, upgrading, repairing, inspecting, dismantling and using the dendrometer. The dendrometer is alternatively known as Band Dendrometer, Tree Hugger™, Tree-Hunger™, TreeHugger™ or Treehugger™, TreeHugger Dendrometer™, TH™ or other similar names. 
       BACKGROUND OF INVENTION 
       [0002]    Dendrometers are metrology or scientific instruments used for measuring various dimensions of trees, such as their diameter, size, shape, age, overall volume and thickness of the bark. One of the most frequently measurements acquired in the field includes DBH (Diameter at Breast Height) of trees. DBH is adopted in estimating the amount of timber volume in a single tree or stand of trees utilizing the allometric correlation between stem diameter, tree height and timber volume. DBH is also employed in estimating the age of veteran trees, given that girth or diameter increment of a tree is the only, constant non-reversible feature of growth. Currently, the two most common dendrometers are a girthing (or diameter) tape and calipers. However, these known instruments often require site visit of personnel to the trees-of-interest, which is costly and tedious for surveying forest tree plots of wide or remote areas. 
       SUMMARY OF INVENTION 
       [0003]    The present invention aims to provide one or more new and useful devices, such as dendrometer. This invention also intends to provide methods for making, assembling, installing, configuring, upgrading, repairing, inspecting, dismantling and using the device. Essential features of the device(s) are provided by independent claims, whilst advantageous features of the device(s) are given by dependent claims. This application claims the priority date of U.S. provisional patent application 61/832,701 that has been filed with USPTO on Jun. 7, 2013. Entire content or subject matter of the earlier priority application is hereby incorporated by reference. 
         [0004]    According to a first aspect, the application provides a dendrometer that comprises a dendrometer band whose length is extendable for encircling a tree trunk or tree branch. The dendrometer is also known as band dendrometer, which is often used to measure circumferences/perimeter of tree trunks or sizes of fruits. The dendrometer further comprises an electronic component that is closely or contiguously attached, fixed or adhered to the dendrometer band over a length period for converting length variation of the dendrometer band to electronic signals. Longitudinal extension of the dendrometer band is facilitated by structure of the dendrometer band, which usually has its range beyond elasticity limit of material(s) of the dendrometer and will not cause irreversible deformation to the dendrometer band. For example, the extension typically is not provided by elastic or plastic behavior of the material(s) of the dendrometer band. In one embodiment, the dendrometer band having two or more stages that provide telescopic extension in its longitudinal direction so that the dendrometer band can hug the tree trunks of various sizes closely or snuggly by extending to suitable length(s). Accordingly, when activated, the electronic component can follow length extension of the dendrometer band and transform length variation or extension movement of the dendrometer band into the analogue or digital electronic signals by the electronic component, such as providing voltage, resistance, inductance and electric current values for indicating the change of tree circumference. In contrast, a foil strain gauge can only operate within its elasticity limit, which merely provides narrow ranges of measurement for dendrometry. Here, the electronic component includes any basic discrete device or physical entity for an electronic system for affecting electrons or their associated fields. The electronic component is usually an industrial product, available in a singular form. Examples of the electronic components contain active components, passive components and electromechanical components. 
         [0005]    The dendrometer has simple construction for reliable operation over a prolonged period of time. Since the dendrometer band can be tightened to the tree trunk non-invasively, accurate measurements can be repeatedly taken without interfering growth of the tree trunk. Long range of extension (e.g. 8-2,400 mm if using SoftPot™ potentiometer) permits years of autonomous operation on tree trunks without human intervention for onsite adjustment, calibration or replacement. The dendrometer has flexibility for being mounted onto tree trunks with wide range of circumferences or diameters because the dendrometer band can elongate or shorten itself without reducing its accuracy in measurement. In fact, the dendrometer band can be customized by cutting it to desired length for fitting any designated object (e.g. tree branch or fruit). Since materials or parts of the dendrometer band and the electronic component are readily available in the market at low cost (e.g. SoftPot™ potentiometer), the dendrometer can be sold at affordable prices, benefiting dendrometry application of dispersed or wide areas of forests or plantations. 
         [0006]    The electronic component can comprise a passive electronic component that includes switch, resistor, capacitor, inductor, transformer, memristor, (RC or LC) network of passive components, transducers, sensors, detectors, antenna, assembly/module (e.g. oscillator, digital voltmeter) and prototyping aids (e.g. wire-wrap, breadboard). In contrast, the active electronic components include semiconductor (e.g. diode, LED), transistor (e.g. thyristor), integrated circuit (digital or analogue), optoelectronic device, light-emitting device (e.g. filament lamp, nixide tube), vacuum tube, optical detector or emitter, and power source (e.g. battery, fuel cell). Since some of the passive electronic components can be made into different forms (e.g. film or sheet) cheaply, the passive electronic component can be fixed onto the dendrometer band in order to follow or capture linear/longitudinal extension of the dendrometer band. For example, an array of switches can be printed onto the dendrometer band such that electrical connection of one or more of the switches provides extent of the linear/longitudinal extension. Electricity consumption of the dendrometer can possibly be greatly reduced for prolonged autonomous operation of the dendrometer because the passive electronic component only consumes electricity when in operation (e.g. taking periodic reading), not necessarily in standby mode. 
         [0007]    The passive electronic component may comprise a potentiometer, variable resistor or rheostat. The potentiometer typically comprises a resistive element and a sliding contact (wiper) that moves along the resistive element for making good electrical contact. For example, Sparkfun™ (distributor) and Spectra Symbol™ in Salt Lake City, Utah (manufacturer) of USA provideSoftPot™ Membrane Potentiometers whose resistance values linearly change from 100 Ohms to 10,000 Ohms, allowing very accurate calculation of relative positions on the Membrane Potentiometers. The potentiometer (alternatively known as membrane potentiometer or membrane switch) comprises a collector, a circuit spacer, a bus bar (resistor), resistor and a bottom adhesive that are sequentially stacked and packaged. Since the potentiometer is sealed against harsh environments, the dendrometer may be made to withstand diverse types of weather conditions. When using a SoftPot™ Membrane Potentiometer of 500 mm active area length, the dendrometer band can measure circumference change of the tree trunk up to 0.5 meter, which is a very long period of growth and observation for trees. Membrane potentiometers may be further customized such that active lengths of the membrane potentiometers can be made from several millimeters to more than a few meters from specific applications or trees. The potentiometer can provide high accuracy of measurement to tree trunks, typically within 10 μm. When in use, the potentiometer can enable the dendrometer to measure changes of circumference of a tree trunk with a resolution of ±6 μm at min sampling interval. 
         [0008]    The dendrometer band can comprise a circuit band for carrying one or more parts of the electronic component, and a plunger band for carrying one or more other parts of the electronic component, such as a plunger/wiper of the potentiometer. The circuit band and the plunger band are configured to cooperate with each other moveably in for sliding in longitudinal directions of the two bands. The two bands may also be partially fixed to each other for providing the electronic signals (e.g. voltage, current). For example, the circuit band includes the collector, the circuit spacer, the bus bars and the resistor that are adhered to a stainless steel band by permanent glue. The wiper or plunger can be mounted (e.g. spring-loaded or spring-plate attached) to a plastic stripe in forming the plunger band. The circuit band and the plunger band may be guided with respect to each other by rails, slots or casings such that the two bands can closely attach to each other and move in their longitudinal directions for achieving telescopic motion (length variation). Of course, parts of the electronic component (e.g. membrane potentiometer) may be exchanged in their position on the two bands depending on requirements. Any of the two bands can be made with light-weight materials, and they can be cut to desired sizes onsite (e.g. near a tree trunk) for customization. 
         [0009]    Preferably, the circuit band, the plunger band, or any parts of the two bands comprise one or more stainless steel (i.e. inox steel) stripes. Since stainless steel material requires little maintenance and can be recycled, life span of the dendrometer is dramatically prolonged, compared to known dendrometers. One way of recycling a stainless steel stripe is to connect its two opposite ends to a dendrometer band so that the dendrometer can measure a trunk with larger circumference. 
         [0010]    In one embodiment, the plunger band comprises a stainless ribbon for mounting a plunger of the potentiometer. Since the stainless steel ribbon provides a wide and robust base for mounting onto a trunk, the plunger band has long-term reliability and durability for operation. 
         [0011]    In another embodiment, the dendrometer band comprises a clip for guiding movement of the circuit band, the plunger band or both. The clip may be in the form of sheet metal folded around one of the bands so that another band can slide within the clip. The clip can be integrally or separately formed on either one of the bands. The clip may further be fixed onto any of the two bands. When in use, the clip prevents the wiper/plunger from working outside active area of the potentiometer. 
         [0012]    The dendrometer band may comprise a stopper (e.g. by welding) for limiting longitudinal movement of the circuit band, the plunger band or both. When using membrane potentiometer, the stopper constrains the wiper/plunger to slide within the active area so that the dendrometer can provide proportional change of potential/resistance depending length variation/extension of the dendrometer. The stopper may be in the form of a stud, a bent-stripe, a rivet, a block or a spring. The stopper may be detachable so that the stopper can be relocated after changing the electronic component (e.g. membrane potentiometer). 
         [0013]    The dendrometer band can further comprise a spring for connecting the circuit band and the plunger band by opposite ends of the spring. The spring is alternatively known as an elastic object used to store mechanical energy. Known examples of the spring include tension/extension spring (based on type of force) or coil spring (based on shape). For example, one end of the spring is detachably linked to a hook on the circuit band, whilst another end of the spring is removably joined to an orifice on the plunger band. Resilient force of the spring makes the dendrometer band to contract/reduce to its minimum length, thus hugging the tree trunk tightly. Hence, the spring ensures that the dendrometer band encircles the tree trunk tightly and snuggly, without losing accuracy due to thermal expansion or contraction of the dendrometer band. Thus, the dendrometer is able to capture a wealth of data relating to short range of contraction and expansion of tree trunks, which are not visible to the naked eye. For example, stems of trees shrink and expand daily in the range of several millimeters due to water circulation in leaves and roots of the trees. The spring enables the dendrometer to follow both expansion and contraction of tree trunks generated by the evaporative demand of the leaves and water supply rate to tree roots. The spring may be replaced by one or more multiple resilient means or extendable devices, such as helical springs, rubber bands, magnetic spring, gas spring, hydraulic spring and bows. 
         [0014]    In a further embodiment, the dendrometer band, the electronic component or both devices are at least partially weatherproof, scratchproof, dustproof, shockproof or having a combination of any of these properties. Dendrometers are often deployed and unattended in forests for long periods of time (e.g. nine months), these components enables the dendrometer to provide consistent performance without site-visit by researchers, engineers or technicians, thus achieving cost and time savings. 
         [0015]    The dendrometer band, the electronic component or both articles are protected against external intrusion of solid particles, liquid ingress, mechanical impact, electric shock or a combination of any of these. For example, the electronic component (e.g. potentiometer) has IP65 (International Protection Marking) prevents ingress of dust and water splashing. These components may be further enhanced for preventing influence of various weather conditions (e.g. snowing) and mechanical impacts (e.g. squirrel scratching). 
         [0016]    In one embedment, the dendrometer has a data logger that is connected to the electronic component for reading the electronic signals. The data logger may include microprocessor(s), solid state memory, RAM (Random Access Memory), battery, PCB (printed Circuit Board), integrated circuit(s), LED (Light Emitting Diode), antenna(s), user interface(s) and other electronic components for data processing and transmission. The data logger may process and store data locally at the solid state memory (e.g. Secure Digital Cards as non-volatile memory cards), or transmit the data to a central location (e.g. a remote station). The data logger may be loaded with an operating system and one or more application software packages such that the data logger can communicate with a computer or a mobile computing device (e.g. tablet computer). 
         [0017]    Another embodiment of the dendrometer further comprises an electric cable for connecting the electronic component to the data logger. The electric cable may have connectors (e.g. type 0L, 1E or 0F, crimp connectors) that allow detachment or connections between the data logger and the dendrometer band conveniently. 
         [0018]    The dendrometer or the data logger may comprise an electrical energy source (e.g. energy harvesting device, energy storage device) for powering the data logger. The energy source provides electricity to the data logger to periodically record data from the dendrometer band for future analysis of one tree or data analytics of many trees. When one or more energy harvesting devices are deployed, the dendrometer can operate autonomously such that a researcher does not have travel to the dendrometer physically for servicing. When required, the dendrometer can send an alert message/signal to a user for servicing when required. 
         [0019]    The data logger can further comprise a memory device (e.g. hard disk drive or memory stick) for data storage or processing locally. Since modern memory devices are cheaply available, one data logger or dendrometer can record and store data for multiple dendrometers or other forest monitoring devices within its vicinity. 
         [0020]    In an embodiment, the data logger or the dendrometer further comprises an antenna (aerial) for radio/wireless signal transmission or reception. The antenna enables digital or analogue communication of the data logger such that the data logger or the dendrometer may be remotely or wirelessly accessed, configured, repaired and upgraded. The dendrometer or data logger may even be internet or satellite accessible. The data logger may include a ZigBee module based on IEEE802.15 standard such that the data logger can provide long battery life and secure networking with low data rate. The data logger may incorporate telecommunication modules for connecting 3G network (Universal Mobile Telecommunications System) such that the dendrometer can be deployed over a wide and remote area by using existing telecommunication networks. 
         [0021]    In a further embedment, the dendrometer band, the electronic component or both comprises markings or inscription for visualizing the length variation. The markings or inscription allows convention metrology tools (e.g. caliper, micrometer) or human visual readings (e.g. with magnifying glass) when calibrating the dendrometer. 
         [0022]    In another embodiment, the dendrometer comprises a data logger that has low cost and low power consumption. High resolution or high accuracy of the dendrometer may not be compromised by the low cost because market price of the electronic component (e.g. potentiometer) is only about US $12.95 currently when buying individually. The dendrometer may include one or more temperature sensors (e.g. thermistor or thermocouple) for measuring local temperature of the dendrometer band so that thermal expansion of the dendrometer band can be compensated by electronic circuit(s) or software program(s) of the data logger. The data logger can include one or more analogue-to-digital converters for converting analogue signals from the electronic component to digital signals for further processing. Examples of analogue-to-digital semiconductor chips include NAU7802 of NuvoTon Technology, AD7705 of Analogue Devices and MCP3424 of Microchips. 
         [0023]    The present application also provides one or more sensor networks that comprise the dendrometer and a gateway sensor node wirelessly connected or cable-connected to the dendrometer. The sensor network(s) can monitor wide variety indicators of a forest so that regulatory authorities and/or research institutions can obtain real-time data for managing forests, combating climate change. 
         [0024]    The application further provides a wireless sensor network that comprises the sensor network and one or more radio transceivers having one or more antennas for communication between the dendrometer, the gateway sensor node or other computing devices. One or more of the wired or wireless sensor network may be inter-connected for county-wide, state-wide or nation-wide monitoring. The wireless sensor network can greatly reduce cost of monitoring, providing real-time information to interested parties. 
         [0025]    According to a second aspect, the application provides a method for using a dendrometer. The method comprises a step of clasping or encircling the dendrometer onto a tree trunk such that the dendrometer can extend its length following circumference growth of (i.e. around) the tree trunk. The method further comprises a step of powering (e.g. providing 2.56 volt DC to) the dendrometer for generating and/or receiving electronic signals. The method also comprises a step of converting the electronic signals to circumference growth data of the tree trunk. Any of these method steps described by the present application may be altered in sequence depending requirements or suitability. The dendrometer can be intuitively used by a technician according to these few steps. A person who has prior experience of using other types of dendrometer will find the dendrometer simple to operate. 
         [0026]    The method may further comprise a step of electrically connecting an electronic component of the dendrometer to a data logger for data processing locally. The data logger can be used to configure, calibrate and monitor performance of the dendrometer after making the electrical connection. 
         [0027]    The method can further comprise a step of transmitting the electronic signals to another electronic device. In other words, two or more electronic devices begin to “talk” (communicate) to each other such that the dendrometer can operate independently or within a network. 
         [0028]    According to a third aspect, the application provides a method for installing a dendrometer. The method comprises a step of providing a dendrometer band that has a circuit band, a plunger band and a clip for guiding movement of the circuit band, the plunger band or both. The method also comprises a step of encircling the dendrometer band around a tree trunk and a step of joining the circuit band and the plunger band by a spring or other elastic means for clasping the tree trunk. Since the installation can be completed by using a hand tool or with free hands, the dendrometer can be attached to a tree trunk easily and reliably. Tedious procedure of adjustment and numerous spare parts are avoided. 
         [0029]    According to a fourth aspect, the present application provides a method for servicing a dendrometer. The method comprises a step of cleaning or adjusting a dendrometer band for giving sufficient range of extension to the dendrometer band. For example, if a SoftPot membrane potentiometer of 500.00 mm (19.685″) is adopted, a plunger/wiper on a plunger band is positioned within the 10 mm at a beginning range of a circuit band after the servicing. Providing the plunger or wiper at the beginning portion of the measuring range maximizes measuring capacity of the dendrometer. Careful cleaning or adjusting of the dendrometer will provide added life span to the dendrometer without incurring much cost and effort. 
         [0030]    The method for servicing the dendrometer can comprise a step of replacing faulty parts of the dendrometer band. Once repaired, the dendrometer resumes its normal operation without additional cost. The component replacement also includes change of batteries or rusty parts. The method of servicing may further include a step of attach or adhere another membrane potentiometer to the dendrometer band to prolong life of the dendrometer. The method of servicing can also include a step of lengthening the dendrometer band by patching another band. 
         [0031]    According to a fifth aspect, the application provides a method for configuring a dendrometer. The method comprises a step of providing a dendrometer band with a circuit band and a plunger band. The application also includes another step of examining range of movements of the circuit band and the plunger band. The method includes a third step of adjusting lengths of the circuit band, the plunger band or both for providing sufficient operation range to an electronic component of the dendrometer when clasping a tree trunk. This method effectively extends useful lifespan of the dendrometer. 
         [0032]    According to a sixth aspect, the application provides a method for making a dendrometer. The method comprises a step of providing a dendrometer band, a step of attaching an electronic component to the dendrometer band for generating electronic signals when extending the dendrometer band, and a step of connecting leads of the electronic component to a cable. The dendrometer can be made with little time and cost, thus benefiting a large pool of users. 
         [0033]    The method of making further comprises a step of presenting a data logger for receiving the electronic signals. The data logger can convert electronic signals to meaningful data for tree growth monitoring. The data logger may be supplied by manufacturers of the dendrometer, or users themselves by configuring existing available data logger(s). 
         [0034]    According to a seventh aspect of the invention, the present application provides a dendrometer that comprises a main belt for attaching to a tree trunk, a secondary belt having a first end fixed onto to the main belt and a second end movable with respect to the main belt; and a spring that is connected between the main belt and the secondary belt for pulling the secondary belt to the main belt. The main belt and the secondary belt are flexible or resilient for wrapping around the tree trunk in order to measure the girth of a tree. The main belt can comprise a folded end that has slots for guiding movement of the secondary belt along the main belt. The dendrometer may further comprise a plunger sensor on the main belt for measuring a distance between the main belt and the tree trunk. The dendrometer can further comprise a SoftPot sensor on the secondary belt for gauging relative movement between the main belt and the second belt. The plunger sensor, the sensor, or both may have ingress protection against water or dirt. The SoftPot sensor can comprise an elongated datable region for determining the change of length with a predetermined range. The dendrometer may further comprise an electronic circuit that is connected to the plunger sensor, the SoftPot sensor or both sensors for taking measurement locally. The electronic circuit can further comprise a data storage device for storing measured data locally. The electronic circuit may further comprise a microprocessor for data processing locally. The electronic circuit can further comprise an antenna for wireless communication. The electronic circuit may further comprise an energy storage device for powering the electronic circuit. The electronic circuit can further comprise a network interface for data communication with another dendrometer or a remote work station. The electronic circuit further may comprise a casing for protecting the electronic circuit against external disturbance. The electronic circuit can further comprises a linear potentiometer configured as a voltage divider within the Softpot sensor to provide a linear voltage signal relative to the plunger position along the length of the SoftPot. The main belt, the secondary belt, the spring or all of them may be made of stainless material, which has a low thermal coefficient and provides a low friction surface against the tree. 
         [0035]    According to an eighth aspect of the present invention, the application provides a method of using a dendrometer. The method comprises a first step of providing a main belt for attaching to a tree trunk; a second step of supplying a secondary belt having a first end and a second end; a third step of fixing the first end onto to the main belt and allowing the second end to be movable with respect to the main belt; a fourth step of wrapping the main belt and the secondary belt around the tree trunk for measuring girth of a tree and a fifth step of connecting a spring between the main belt and the secondary belt for pulling the secondary belt to the main belt. Some of these steps may be changed in sequence for achieving similar results. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0036]    The accompanying figures (Figs.) illustrate one or more embodiments, and serve to explain principles of the disclosed embodiment(s). It is to be understood, however, that these figures are presented for the purpose of illustration only, and not for defining limits of relevant inventions. Exemplary, non-limiting embodiment(s) of the present invention will now be described with reference to the above-mentioned figures. 
           [0037]      FIG. 1  illustrates a dendrometer that is installed on a tree trunk; 
           [0038]      FIG. 2  illustrates bands of the dendrometer that are extended in their longitudinal directions; 
           [0039]      FIG. 3  illustrates the dendrometer band as assembled, but not mounted onto the tree trunk; 
           [0040]      FIG. 4  illustrates a clip of the dendrometer; 
           [0041]      FIG. 5  illustrates a membrane potentiometer of the dendrometer; 
           [0042]      FIG. 6  illustrates a schematic diagram of a data logger for the potentiometer; 
           [0043]      FIG. 7  illustrates measurement results of the tree trunk over one month by using the dendrometer; and 
           [0044]      FIG. 8  illustrates a sensor network that utilizes the dendrometer. 
       
    
    
     DETAILED DESCRIPTION 
       [0045]      FIGS. 1-8  provide an embodiment of the present invention. Parts of the embodiment are labeled by identical or similar reference numerals. Description that corresponds to the identical or similar reference numerals is hereby incorporated by reference, wherever relevant or appropriate. 
         [0046]    Particularly,  FIG. 1  illustrates a dendrometer  20  that is installed on a tree trunk  22 . The dendrometer  20  comprises a data logger  24  and a dendrometer band  26  that are connected via a cable  28 . The data logger  24  is mounted onto the tree trunk  22  via a stainless belt  30 , which wraps around the tree trunk  22 . The dendrometer band  26  includes a circuit band  32  and a plunger band  34  that are closely attached and overlap partially. A first end  35  of the circuit band  32  and a first end  37  of the plunger band  34  are connected by a first rivet  39  such that they are serially connected, as shown in  FIG. 2 . The dendrometer band  26  further comprises a spring  36  whose opposite ends are connected to the circuit band  32  and the plunger band  34  respectively. 
         [0047]      FIG. 2  illustrates the bands  32 ,  34  of the dendrometer band  26  that are extended in their longitudinal directions. The plunger band  34  has a stainless steel strip (i.e. ribbon or belt)  38  and a plunger  40 . The stainless steel strip  38  has a width of 20 mm (millimeter), a length of about 450 mm and a thickness of 0.5 mm. The plunger  40  includes a standard wiper  42  and a cylindrical casing  44  such that the standard wiper  42  is inserted into the cylindrical casing  44 , and they  42 ,  44  are both perpendicular to a broad surface (length versus width) of the plunger band  34 . The standard wiper  42  is spring-loaded via a screw (not shown) in the cylindrical casing  44 . 
         [0048]    The circuit band  32  includes a stainless steel ribbon (i.e. belt or strip)  46 , an anchoring tag  48 , a membrane potentiometer  50  and a clip  52 . The stainless ribbon  46  has a width of 20 mm (millimeter), a length of about 520 mm and a thickness of 0.5 mm. The anchoring tag  48  is a riveted fixture with an extension ring (not shown) and a thermistor  68 . The membrane potentiometer  50  is a SoftPot™ Membrane Potentiometer of 200 mm length (SEN-08679 RoHS), which is provided by Spectra Symbol of Salt Lake City, Utah 84119, USA. The membrane potentiometer  50  may be simply known as potentiometer, variable resistor or rheostat. Both the thermistor  68  and the membrane potentiometer  50  are connected to the data logger  24  via the cable  28 . The clip  52  is a folded stainless strip, and the clip  52  is fixed to the end of the circuit band  32 . The clip  52  further provides a slot  59  such that the plunger band  34  can slide within the clip  52  for extending length of the dendrometer band  26 . The membrane potentiometer  50  is adhered to a broad side (length versus width) of the stainless steel ribbon  46 , and mutually aligned in their longitudinal directions. The membrane potentiometer  50  comprises a connector  54 , which is a Crimpflex solder tab for attachment of the cable  28 . 
         [0049]      FIG. 3  illustrates the dendrometer band  26  as assembled, but not mounted onto the tree trunk  22 . In this form, the plunger band  34  has been serially connected to the circuit band  32  by the first rivet  39  such that they  34 ,  32  form an elongated ribbon or belt. The plunger band  34  is further inserted through the gap  59  on the clip  52  that is fixed to an end of the circuit band  32 . Respective movement between plunger band  34  and the circuit band  32  is limited by the clip  52  and the plunger  40  because the plunger  40  cannot move beyond the clip  52 . 
         [0050]    The spring  36  has two ends that are at opposite ends, consisting of a plunger end  63  and a circuit end  65 . The plunger end  63  is hooked to an end  67  of the plunger band  34 , whilst the circuit end  65  is to be joined to a riveted tag  69  (not visible) on the circuit band  65 . Of course, when installing the dendrometer band  26  in the field (e.g. forest plantation), the first rivet  39  may be only connected after adjusting and mounting the spring  36 . 
         [0051]      FIG. 4  illustrates the clip  52  of the dendrometer  20 . The clip  52  is made from a single stainless steel sheet, which is folded with two wings  55 ,  57 . The clip  52  has a base  58  that is substantially parallel to the two wings  54 ,  56  respectively. A first wing  55  and a second wing  57  have a gap  61  of 5 mm in-between them throughout a length of the clip  52  (in a vertical direction of  FIG. 4 ). Furthermore, each of the first wing  55  and the second wing  57  are detached from the base  58 , creating the slit  59  of 0.6 mm for receiving and sliding plunger band  34 . 
         [0052]      FIG. 5  illustrates the membrane potentiometer  50  of the dendrometer  20 . The membrane potentiometer  50  is a resistive element, which comprises a conductive resistor (bottom circuit and top circuit), a sealed encasement and a simple wiper  42  assembly. The membrane potentiometer  50  can also function as a voltage divider. In use, by pressing the standard wiper  42  down onto a top circuit, the membrane potentiometer  50  produces desired electrical output. The standard wiper  42  is a non-conductive mechanism that depresses the top circuit actuating the membrane potentiometer  50  from the outside of the circuits. The top and bottom circuits are separated by 0.15 mm (0.006″) of spacer adhesive build-up and contact between the circuits occurs by pressure (usually 1 to 3 Newton) from the wiper  42  on the top circuit, pushing down until the top circuit connects with the bottom circuit for creating an electrical potentiometric output. The membrane potentiometer  50  has a three-wire system with two resistive output channels and an electrical collector channel. The electrical collector channel is activated by the standard wiper  42  when pressed again the top circuit and bottom circuit. In  FIG. 5 , three electrical leads of the connector  54  are exposed, which consist of Pin A (i.e. Pin 1 connected to bottom bus bar, V+)  56  for receiving positive voltage potential, Pin B (Pin 2) 58  as input pin for connecting to the collector or plunger  40  and Pin C (Pin 3)  60  for joining the Ground potential (GND) or top bus bar. The potentiometer  50  generally has several layers that are sequentially attached together, which includes bottom adhesive layer, bus bar(s), resistor, circuit spacer and collector. 
         [0053]      FIG. 6  illustrates a schematic diagram of the data logger  24  for the potentiometer  50 . The data logger  24  has a microcontroller (microprocessor)  62 , an EEPROM (Electrically Erasable Programmable Read-Only Memory)  64 , a PC (personal computer) interface  70 , an Analog-to-Digital Converter  72 , an amplifier  74 , a potentiometer connector  76  and an antenna  78 . The EEPROM  64 , the Analog-to-Digital Converter  72  and the PC interface are connected to the microcontroller  62  such that preloaded operating system and data logging application software package can operate automatically for data collection and transmission. The potentiometer connector  76  is connected to the Analog-to-Digital Converter  72  via the amplifier  74  such that minor voltage signals can be augmented and filtered for processing by the microcontroller  62 . The antenna  78  (aerial) is connected to the microcontroller  62  for providing wireless communication by a data logger application software package. 
         [0054]      FIG. 7  illustrates measurement results of the tree trunk over one month period by using the dendrometer  20 . The tree trunk belongs to a sugar maple tree in central Illinois State, which is measured by the dendrometer band (TreeHugger™) with onboard data storage (SD card). Raw data (orange colored) have been illustrated together with temperature-corrected (thermal expansion compensated) data (blue colored). These data correspond very well with manually obtained data by using a Vernier Caliper. 
         [0055]      FIG. 7  indicates that the dendrometer  20  is able to capture circumference variation of the tree trunk  22  over a relatively short period automatically. Data of  FIG. 7  clearly indicates the consistent growth rate of the tree trunk  22  at about 0.076 mm/day, which is otherwise not discernable by conventional manual measurement technique. Reliable, accurate and real-time data of tree growth will greatly facilitate tree cultivation and forest plantation. In fact, the dendrometer  20  is so accurate that measurement data of the dendrometer  20  are subjected to temperature variations of its ambient environment. 
         [0056]    Effect of thermal expansion and contraction on the dendrometer band  26  has been calibrated for further improvement of measurement accuracy. The effect of thermal expansion has been calculated according to following equation: 
         [0000]      Δ X=L*ΔT*C   TE   (Equation A)
 
       Where 
       [0057]    Δx means the change in length;
 
L means the length of material;
 
ΔT means the change in temperature (degree Celsius); and
 
C TE  means the coefficient of thermal expansion.
 
         [0058]    Since the membrane potentiometer  50  is adhered to the stainless steel ribbon  46  by a strong adhesive backing of 3M™, the adhered membrane potentiometer  50  has the coefficient of thermal expansion (C TE ) of about 14.82 μm/m° C. (micrometers per meter per degree Celsius). In contrast, an un-mounted (non-installed) membrane potentiometer  50  has the coefficient of thermal expansion (C TE ) of about 23.29 μm/m° C. In other words, thermal expansion of the membrane potentiometer  50  has been adapted to the thermal expansion of the stainless steel ribbon  46  after assembling or installation. 
         [0059]    Compensation of thermal expansion to the dendrometer band  26  is calculated by taking reference from a base point, which is provided by using Equation B (see below). This base point provides the reference for the change in temperature. The change in temperature is multiplied by the previous recorded diameter of the trunk  22  and the coefficient of thermal expansion. 
         [0000]      Δ X=D   L ( T−T   B )* C   TE   (Equation B)
 
         [0000]      Δ T=T−T   B   (Equation C)
 
       Where: 
       [0060]    Δx means the change in length;
 
D L  means the previously recorded diameter of the trunk;
 
T means temperature value (degree Celsius) of the recording of interest;
 
T B  means temperature value (degree Celsius) of the previous recording as reference (base point); and
 
C TE  means the coefficient of thermal expansion.
 
         [0061]    According to experimental results by using above-mentioned equations, the coefficient of thermal expansion for the membrane potentiometer  50  is 23.29 μm/° C., the coefficient of thermal expansion for the adhered/assembled the membrane potentiometer  50  on the circuit band  32  is about 14.82 μm/° C. Since the coefficient of thermal expansion for the stainless steel banding is about 14.83 μm/° C., the coefficient of stainless steel can be used for the thermal expansion correction Equations A˜C without affecting measurement accuracy. 
         [0062]      FIG. 8  illustrates a sensor network  220  that utilizes the dendrometer  20 . The sensor network  220  comprises sensor nodes  20 ,  201 - 207 , a gateway node  210 ,  20  and base station  212 . Each of the sensor nodes  20 ,  201 - 207  and the gateway node  210 ,  20  comprises a radio transceiver with an internal antenna or connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or an embedded form of energy harvesting, which are not shown. The base station  212  is connected to these nodes  20 ,  201 - 207 .  210  via one or more forms of low energy wireless network (e.g. ZigBee based on IEEE 802.15 standard) such that the base station  212  can obtain real-time data of tree trunk growth and configure these nodes in response to temperature (e.g. due to season change). 
         [0063]    [Method of Use] 
         [0064]    In use, bark of the trunk  22  is trimmed for providing two parallel narrow strips of relatively smooth surface around the trunk  22 . Inner bark of the trunk  22  is prevented from the trimming so that normal growth of the trunk  22  is not affected by the trimming. In other words, living tissue of the trunk  22  is not affected by the trimming. 
         [0065]    For installation, the plunger band  34 , the circuit band  32  and the data logger  24  are taken to the trunk  22  for installation. The plunger  40  is readily fitted onto the plunger band  34 . A free end  67  of the plunger band  34  is inserted into the clip  52  such that the plunger band  34  can slide along the circuit band  32 . Two opposite ends  63 ,  65  of the stainless spring  36  are hooked to the free end  67  and the rivet tag  69  such that the plunger band  34  and the circuit band  32  are linked together in forming a single long belt  26 . 
         [0066]    The single long belt  26  is wrapped around the trunk  22  such that overlapped parts (not shown) of the two bands  32 ,  34  are marked out. The overlapped parts are trimmed off, leaving sufficient portions for riveting the two bands  32 ,  34  together. The stainless spring  36  may be taken off when trimming the bands  32 ,  34  for convenience. Particularly, the standard wiper  42  is located with 10% of the beginning portion of the membrane potentiometer  50  when marking and trimming the overlapped parts. After riveting the two ends  35 ,  37 , the two opposite ends  63 ,  65  of the stainless steel spring  36  are hooked back to the dendrometer band  26  at the end of the plunger band  67  and the riveted tag  69  on the circuit band  32 . 
         [0067]    The stainless steel belt  30  is inserted through a mounting slot (not shown) of the data logger  24 . The stainless steel belt  30  is tied around the trunk  22  such that the data logger  24  is slight above and adjacent to the plunger  40 . The connector  54 , which is at the end of the cable  28 , is plugged into the data logger  24  such that electrical connection is established between data logger  24  and the dendrometer band  26 . 
         [0068]    For data logging, the data logger  24  is switched on so that application software of the dendrometer  20  starts to operate. The data logger  24  comprises a lithium battery (not shown), a temperature sensor (thermocouple), a circuit board (not shown) having microprocessor (not shown) and a solid state memory (not shown). Initial values of trunk circumference and local temperature are entered into the data logger  24  via configuration files held within a SD (Secure Digital) card. After configuration, the data logger  24  operates autonomously for recording variations of the circumference values of the trunk  22 . These values are recorded locally at the solid state memory, and transmitted wirelessly to a remote station via the antenna  78 . 
         [0069]    [Method of Configuring or Repairing] 
         [0070]    Periodically, a technician, engineer or researcher visits the dendrometer  20 , which is installed on to the trunk  22  in a remote forest. The technician firstly opens a cover (not shown) of the data logger  24  so that he replaces depleted lithium battery with a new fully-charged battery. Both external surfaces and internal electrical terminals of data logger  24  are cleaned for returning the data logger  24  back to the optimum condition. The dendrometer band  26  is also cleaned such that rust and debris are removed from exposed parts of the dendrometer band  26 . Particularly, the plunger  40 , the standard wiper  42  and contacting portion of the membrane potentiometer  50  are thoroughly cleaned, free from debris. The technician further cut off the riveted joint  39  that connects the circuit band  32  and the plunger band  34 . An additional stainless band of similar width is provided for connecting the circuit band  32  and the plunger band  34  together. A suitable length of the additional stainless band is provided such that the standard wiper  42  will return to the beginning 10% portion of the membrane potentiometer  50  (collector and resistor). If necessary, the stainless spring  36  is replaced when hooking the circuit band  32  and the plunger band  34  together again. Other parts of the dendrometer  20  may also be replaced when necessary. 
         [0071]    In the application, unless specified otherwise, the terms “comprising”, “comprise”, and grammatical variants thereof, intended to represent “open” or “inclusive” language such that they include recited elements but also permit inclusion of additional, non-explicitly recited elements. 
         [0072]    As used herein, the term “about”, in the context of concentrations of components of the formulations, typically means +/−5% of the stated value, more typically +/−4% of the stated value, more typically +/−3% of the stated value, more typically, +/−2% of the stated value, even more typically +/−1% of the stated value, and even more typically +/−0.5% of the stated value. 
         [0073]    Throughout this disclosure, certain embodiments may be disclosed in a range format. The description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. 
         [0074]    It will be apparent that various other modifications and adaptations of the application will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the application and it is intended that all such modifications and adaptations come within the scope of the appended claims. 
       REFERENCE NUMERALS 
       [0000]    
       
           20  dendrometer 
           22  tree trunk 
           24  data logger 
           26  dendrometer band 
           28  cable 
           30  stainless belt 
           32  circuit band 
           34  plunger band 
           35  first end of the circuit band 
           36  spring 
           37  first end of the plunger band 
           38  stainless steel strip 
           39  first rivet 
           40  plunger 
           42  standard wiper 
           44  cylindrical casing 
           46  stainless steel ribbon 
           48  anchoring tag 
           50  membrane potentiometer 
           52  clip 
           54  connector 
           55  first wing 
           56  Pin A 
           57  second wing 
           58  Pin B 
           59  slit 
           60  Pin C 
           61  gap 
           62  microcontroller 
           63  plunger end 
           64  EEPROM 
           65  circuit end 
           67  end of the plunger band 
           68  thermistor 
           69  riveted tag 
           70  PC interface 
           72  Analog-to-Digital Converter 
           74  amplifier 
           76  potentiometer connector 
           78  antenna 
           201  sensor node 
           202  sensor node 
           203  sensor node 
           204  sensor node 
           205  sensor node 
           206  sensor node 
           207  sensor node 
           210  gateway node 
           212  base station