Patent Publication Number: US-2023152264-A1

Title: Method and device for measuring humidity indicative of moisture in a structure

Description:
TECHNICAL FIELD 
     The present invention relates to a method for measuring humidity indicative of moisture in a structure, for example in a structure of a recreational vehicle or a caravan. The present invention also relates to a device for measuring humidity indicative of moisture in a structure, and to a system comprising a plurality of such devices. 
     BACKGROUND 
     One of the costliest damages that can happen to a recreational vehicle or caravan is ingress of water causing moisture (dampness) in the floor, walls, and ceiling/roof of the recreational vehicle or caravan. This often leads to extensive and expensive repairs, bad smell, and a large decrease in value when reselling the recreational vehicle or caravan. 
     Manufacturers of recreational vehicles and caravans issue guarantees with respect to ingress of water, but the guarantee requires a yearly check of any presence of moisture. Insurance companies also has insurances that covers ingress of water, but with the same requirement of check-up. 
     However, water ingress check-ups (inspections) are costly, and requires that the recreational vehicle or caravan is in the workshop or that service personnel comes to the recreational vehicle or caravan. 
     Overall, one can say that damages due to moisture is the recreational vehicle/caravan industry’s unsolved problem. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome or at least alleviate the aforementioned problem(s), and to provide an improved method and device for (indirectly) measuring moisture in a structure of especially a recreational vehicle or caravan. 
     According to a first aspect of the present invention, this and other objects is achieved by a method for measuring humidity indicative of moisture in a structure, wherein the method comprises: providing a measuring device comprising a housing and a tubular element, wherein the housing accommodates humidity sensor electronics of a humidity sensor of the measuring device, a battery, and wireless communication means, wherein the battery is adapted to power the humidity sensor and the wireless communication means, wherein the wireless communication means is adapted to wirelessly transmit measurement data of the measuring device to a remote apparatus, wherein the tubular element extends from the housing and forms a channel adapted to provide air, which air is affected by moisture of the structure via at least one opening in the tubular element, to a humidity sensor element of said humidity sensor, wherein the tubular element of the measuring device is arranged in a hole of the structure, wherein the housing of the measuring device is positioned on or over a surface of the structure surrounding said hole of the structure and exposed to ambient air, except (possibly) a surface of the housing facing said surface of the structure; and measuring the humidity of the moisture-affected air, which humidity is indicative of moisture in the structure, using the humidity sensor of the measuring device, while the tubular element of the measuring device is arranged in the hole of the structure and while the housing of the measuring device is positioned on or over said surface of the structure surrounding said hole of the structure and exposed to ambient air, except (possibly) the surface of the housing facing said surface of the structure. 
     According to a second aspect of the invention, there is provided a device for measuring humidity indicative of moisture in a structure, wherein the device comprises: a non-embedded housing accommodating humidity sensor electronics of a humidity sensor of the device, a battery, and wireless communication means, wherein the battery is adapted to power the humidity sensor and the wireless communication means, and wherein the wireless communication means is adapted to wirelessly transmit measurement data of the device to a remote apparatus; and a tubular element extending from the housing, wherein the tubular element is arrangeable in a hole in the structure, and wherein the tubular element forms a channel adapted to provide air, which air is affectable by moisture of the structure via at least one opening in the tubular element, to a humidity sensor element of said humidity sensor. This aspect may exhibit the same or similar features and technical effects as the first aspect, and vice versa. 
     ‘Non-embedded’ may mean that the housing, also in normal use when humidity/moisture is measured, never is embedded in the structure. Instead, the housing may be position on or over a surface of the structure surrounding the aforementioned hole in which the tubular channel is (to be) arranged. Apart from the housing surface facing said surface of the structure, the housing may remain exposed to the ambient (air) when humidity/moisture is measured by the device. 
     The present invention is based on the understanding that humidity indicative of moisture in a structure, for example the floor or wall or ceiling of a recreational vehicle or caravan, readily can be measured - preferably continuously or repeatedly - using the battery driven and wirelessly communicating measuring device(s) as defined hereinabove. In this way, the aforementioned yearly inspections can be avoided. 
     Also, since humidity/moisture is measured using the tubular element arranged in a hole of the structure, i.e. inside the structure, a water leak may be detected before it is noticeable on the outside of the structure, whereby damage due to moisture, and subsequent mould and rot damage, can be reduced or eliminated. For example, (humidity caused by) moisture in a structure with aluminium plates on both sides can easily be measured with the present method and device, something that is not possible with typically used manual measurements in recreational vehicles and caravans. 
     Furthermore, since only the tubular element of the measuring device is arranged in a hole of the structure, whereas the housing of the measuring device is on the outside of the structure, the measuring device a) can be mounted on a relatively thin surface component (e.g. 1-6 mm) followed by some insulation material or woodwork of the structure, b) can easily be retrofitted to a structure of an existing recreational vehicle or caravan, and c) requires a relatively small hole in the structure, thereby having little effect on the structure. 
     Also, since the housing is exposed on the outside of the structure, the housing can readily be accessed without having to uncover the housing, for example when changing the battery. 
     It can be noted that US20140216143, unrelated to recreational vehicles and caravans, discloses a body part comprising an embeddable tube separating a space and at least one hole or opening or the like. An upper part of the body part is provided such that data and energy transferring electronics for e.g. data and energy transfer fits inside. A sensor is connected with the electronics and located in such a way that it can measure the moisture content in the separated space. A water vapor penetrating filter placed to protect the sensor and the electronics from extraneous substances. 
     However, the body part in US20140216143 is embedded in a material to be measured during its casting such that the distal end surface of the upper part is provided in the same level with the surface of the material. And in the measuring process when the structure is in normal use, the body part has been covered with insulation material and/or coating, as can be seen in  FIG.  3    of US20140216143. Hence, the body part in US20140216143 is mounted in a completely different way than the present measuring device. 
     The present humidity sensor may be a capacitive humidity sensor or a resistive humidity sensor, for example. 
     The humidity sensor element (of the humidity sensor) may be arranged in the housing. 
     As indicated above, the structure may be included in a recreational vehicle (motorhome) or a caravan. The structure may for example be the floor or a wall or the ceiling of the recreational vehicle or caravan. Alternatively, the structure could be included in some other mobile unit, such as an isolated trailer (for refrigerated transport), an isolated container, etc. Basically, the present invention could be used for any type of wall, floor, or ceiling/roof (-’structure”) where moisture damage could occur. 
     As indicated above, the humidity may be measured continuously or repeatedly, for example once every second day. 
     Furthermore, a surface of the housing surrounding the tubular element may be provided with adhesive means. The adhesive means may for example be a double sided (foam) tape, but other adhesive means - such as glue - could be used as well. Apart from facilitating mounting of the (measuring) device to the structure, the present inventor has realized that the adhesive means also may prevent that the humidity of the ambient air (negatively) affects the measurement, which in turn provides for a more accurate measurement. To this end, the adhesive means preferably forms a continuous area around the tubular element. In other words, the adhesive means/continuous area acts as a seal between the ambient air and the hole in the structure. 
     The at least one opening in the tubular element may be a plurality of longitudinal slots. As the slots are longitudinal, the humidity measurement can be influenced by moisture from a range of depths (corresponding to the length of the longitudinal slots) possibly covering different layers in the structure. Furthermore, the plurality of longitudinal slots could be (uniformly) distributed about the circumference of the tubular element, whereby the humidity measurement can be influenced by moisture from different directions. 
     A portion of the tubular element closest to the housing may be circumferentially closed and devoid of said at least one opening. This portion of the tubular element may for example be an open or hollow cylinder. This portion has several advantages. It may allow measurement in the right place (depth) in the structure. Furthermore, it may protect the humidity sensor element from debris from the structure. Furthermore, it may allow this portion of the tubular element to function as an integrated humidity chamber, thereby forming an air gap (with the moisture-affected air) between the humidity sensor element and the structure. 
     A free end portion of the tubular element opposite the housing may be pointed. This may serve to centre the tubular element and the humidity sensor element when the tubular element of the (measuring) device is inserted in the hole in the structure. 
     The housing may include a partition such that the humidity sensor element is exposable for the air affectable by moisture of the structure but not the humidity sensor electronics, battery, and wireless communication means. This may ensure proper functionality and prolong the lifetime of the humidity sensor electronics, battery, and wireless communication means. The partition is conveniently formed by a portion of a printed circuit board in the housing, on which portion the humidity sensor element is mounted, and a ring-shaped element surrounding the humidity sensor element. Hence, no filter in front of the humidity sensor element is needed in the present (measuring) device. 
     According to a third aspect of the invention, there is provided a system, comprising: a plurality of devices according to the second aspect of the invention; and a remote apparatus comprising communication means adapted to receive measurement data wirelessly from the plurality of devices and to transmit the received measurement data wirelessly to a server. 
     The devices may be mounted to different structures of a recreational vehicle or caravan, for example one or more devices in the floor, one or more devices in the walls, and one or more device in the celling. 
     The server, which may be included in the system, may be adapted to receive the measurement data transmitted by the remote apparatus, and to detect if a water leak has occurred based on relative humidity data in the received measurement data. The server may for example detect that a water leak has occurred if the relative humidity data in the measurement data of at least one of the devices exceeds a threshold, for example 80% RH. 
     The measurement data of each device may be accompanied by a device identifier, wherein the server further is adapted to detect where a water leak has occurred based on the device identifiers. The server may here consult a record which specifies to which structure (e.g. the floor, a wall, or the ceiling of a recreational vehicle or caravan) each device is mounted. 
     To improve the accuracy of the water leak detection, the server may take into account natural fluctuations in humidity, preferably by comparing the relative humidity data of each device to an average of the relative humidity data of all of the plurality of devices and/or the ambient air humidity (measured e.g. by a conventional hygrometer) at a given time. For example, if the relative humidity measured by one of the devices increases from one time to another to a high level, generally indicating a water leak, it may be that the later measurement does not deviate significantly from the average measured relative humidity at that time because of more humid weather, whereby the server may refrain from detecting that a water leak has occurred. In another example, if the relative humidity measured by one of the devices is constant from one time to another, generally indicating no water leak, it may be that the later measurement is significantly higher than the average measured relative humidity at that time, which average has decreased because of dryer weather, whereby the server nevertheless may detect that a water leak has occurred. 
     The measurement data may further comprise temperature data provided by a temperature sensor in each device, wherein the server is adapted to detect a water leak or (potential) moisture damage taking into account at least one dew point calculated based on the relative humidity data and the temperature data in the received measurement data. By measuring both relative humidity and temperature, it is possible to calculate when condensation occurs (dew point). For example, 60% RH in warm weather may not result in condensation, whereas 60% RH in cold weather may result in condensation, wherein condensation increases the risk of moisture damage. Hence, in the former case the sever may not “detect” (potential) moisture damage, but in the latter detect (potential) moisture damage for the same RH, which leads to accurate (potential) moisture damage detection. 
     The server further may further be adapted to issue or cause issuance of an alarm if it detects that a water leak (or moisture damage) has occurred. The alarm may for example be issued as a message or notification to a smartphone or the like of the owner of a recreational vehicle or caravan in which the system is installed. The server may further be adapted to issue, or cause issuance of, a warning if the relative humidity data in the measurement data of at least one of the devices exceeds a lower threshold, for example 60% RH. The warning may likewise be issued as a message or notification to a smartphone or the like of the owner of a recreational vehicle or caravan in which the system is installed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing a currently preferred embodiment of the invention. 
         FIG.  1   a    is a cross-sectional perspective view of a measuring device according to an embodiment of the second aspect of the present invention. 
         FIG.  1   b    shows an enlarged detail of the measuring device in  FIG.  1   a   . 
         FIG.  2    is a perspective view, slightly from below, of the measuring device of  FIGS.  1   a - b   . 
         FIG.  3    is a bottom view of the measuring device of  FIGS.  1   a - b   . 
         FIG.  4    is a cross-sectional perspective view of the measuring device of  FIGS.  1   a - b   , when mounted to a structure. 
         FIG.  5    is a flowchart of a method according to an embodiment of the first aspect of the present invention. 
         FIG.  6    illustrates a system according to an embodiment of the third aspect of the present invention, which system is installed in a recreational vehicle. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1   a - b  and  2 - 3    illustrate a device  10  for measuring moisture in a structure  12  (the structure  12  is shown in  FIG.  4   ). 
     The device  10 , which may also be referred to as a measuring device  10 , comprises a housing  14 . The housing  14  may be shaped substantially like a disk or puck or (low) cylinder. The housing  14  has a flat underside  16 , a top side  18 , and a side wall  20  connecting the flat underside  16  and the top side  18 . The top side  18  and the side wall  20  could be made in one piece, which one piece  18 ,  20  may be removably attached to the flat underside  16 . 
     The housing  14  accommodates (houses) a humidity sensor  22   a - b , a battery  24 , and wireless communication means  26 . That is, the humidity sensor  22   a - b , the battery  24 , and the wireless communication means  26  are provided in(side) the housing  14 . 
     The humidity sensor is adapted to measure relative humidity (RH), whereby measurement data of the device  10  may include relative humidity data. The humidity sensor may be a capacitive humidity sensor or a resistive humidity sensor, for example. The humidity sensor includes a humidity sensor element  22   a  and humidity sensor electronics  22   b . The humidity sensor element  22   a  and humidity sensor electronics  22   b  are mounted on, and interconnected via, a printed circuit board  28  in the housing  14 . The printed circuit board  28  may be parallel to the flat underside  16 . 
     The battery  24  is connected to, and adapted to power, the humidity sensor  22   a - b  and the wireless communication means  26 . The battery  24  may be placed on the printed circuit board  28 . The battery  24  may be replaceable, and it can be accessed by temporarily removing the aforementioned one piece  18 ,  20  from the flat underside  16  of the housing  14 . 
     The wireless communication means  26  is adapted to wirelessly transmit the measurement data of the device  10  to a remote apparatus ( FIG.  6   ). The wireless communication means  26  could for example be a Bluetooth unit. Alternatively, the wireless communication means  26  could be based on UHF proprietary radio, ZigBee, ANT, etc. The wireless communication means  26  may be mounted on the printed circuit board  28 . An antenna of the wireless communication means  26  may be arranged along the perimeter of the printed circuit board  28 . 
     The device  10  may further comprise a temperature sensor  27 , whereby the measurement data of the device  10  may further include temperature data. The temperature sensor  27  may be position on the printed circuit board  28 , near the humidity sensor element  22   a . 
     The device  10  further comprises a tubular element  30  extending from the housing  14 . Namely, the tubular element  30  extends perpendicularly from the flat underside  16  of the housing  14 . The tubular element  30  may have a length in the range of 2-4 cm, preferably approximately 3 cm. The tubular element  30  may be circular in cross-section. The (maximum) diameter of the tubular element  30  may be about 6 mm. 
     The tubular element  30  forms a channel  32 . The channel  32  is adapted to provide air A, which air A in use is affected (dampened) by moisture M of the structure  12  (see  FIG.  4   ) via at least one opening  34   a - d  in the tubular element  30 , to the humidity sensor element  22   a  in the housing  14  (via an aperture  36  in the flat underside  16  of the housing  14 ). The channel  32 , aperture  36 , and humidity sensor element  22   a  may be coaxially arranged. 
     The at least one opening  34   a - d  may be a plurality of longitudinal slots  34   a - d . As such, the longitudinal slots  34   a - d  are elongated, and extend generally parallel to a (central) longitudinal axis  38  of the tubular element  30 . The number of longitudinal slots  34   a - d  is here four, but could alternatively be two or three, for example. The longitudinal slots  34   a - d  may be of equal size, shape, and position, except that they are uniformly distributed about the circumference of the tubular element  30 , i.e. one at 0/360 degrees, one at 90 degrees, one at 180 degrees, and one at 270 degrees (see  FIG.  3   ). The longitudinal slots  34   a - d  may for example have a length in the range of 1.5-2 cm, and a width of about 1.5 mm. 
     A portion  40  of the tubular element  30  closest to the housing  14  is preferably circumferentially closed, and hence devoid the longitudinal slots  34   a - d . In other words, the longitudinal slots  34   a - d  do not extend on the portion  40 . The portion  40  may for example be an open or hollow (right circular) cylinder. The length of the portion  40  may for example be about 5 mm. 
     Furthermore, the free end portion  42  of the tubular element opposite the housing  14  may be pointed, as shown in for example  FIGS.  1   a  and  2   . The longitudinal slots  34   a - d  may partly extend on this pointed free end portion  42 . The length of the free end portion  42  may for example be about 25 mm. 
     Furthermore, a surface of the housing  14  surrounding the tubular element  30 , i.e. the flat underside  16 , may be provided with adhesive means  44 , for example a double sided foam tape. The adhesive means  44  preferably forms a continuous area around the tubular element  30 , as can be seen in particular in  FIG.  3   . The adhesive means  44  may cover substantially the complete underside  16 . 
     Furthermore, the housing may include a partition formed by a portion  46  of the printed circuit board  28 , on which portion the humidity sensor element  22   a  is mounted, and a ring-shaped element  48  surrounding the humidity sensor element  22   a . Namely, the ring-shaped element  48  is arranged around the aforementioned aperture  36 , extends from the flat underside  16  towards the inside of the housing  14 , and is closed off by said portion  46  of the printed circuit board  28 , on which portion  46  the humidity sensor element  22   a  is mounted such that it faces and is in fluid communication with the aforementioned channel  32  of the tubular element  30 . In this way, only the humidity sensor element  22   a  may be exposed to the (damp) air A, but not the humidity sensor electronics  22   b , battery  24 , and wireless communication means  26 , which are either on the opposite side of the ring-shaped element  48  or on the opposite side of the printed circuit board  28 . The partition may be sealed by a ring-shaped seal  50 . 
     In use, when humidity indicative of moisture in the structure  12  is measured, the measuring device  10  is mounted to the aforementioned structure  12 , see  FIG.  4   . 
     Namely, the tubular element  30  of the measuring device  10  is arranged in a hole  52  of the structure  12 . The hole  52  extends from a surface  54  of the structure  12  and into the structure  12 . The hole  52  may for example be a bore hole. The hole  52  usually has a bottom  56 . 
     The housing  14  of the measuring device  10 , on the other hand, is on the outside of the structure  12 . Specifically, the housing  14  is positioned on the surface  54  of the structure  12  (which surface  54  thus surrounds the hole  52 ), whereby the housing  14  - apart from the flat underside  16  which faces the surface  54  of the structure  12  - is exposed to ambient air  58 . The measuring device  10  is secured to the structure  12  by the aforementioned adhesive means  44 . 
     Moisture M in the structure  12  affects (dampens) via at least one of the longitudinal slots  34   a - d  the air A in the channel  32  between the structure  12  and the humidity sensor element  22   a  (especially at portion 40). In other words, the concentration of water vapour present in the (damp) air A is influenced by the moisture M in the structure  12 . The channel  32  provides the damp/dampened air A via the aperture  36  to(wards) the humidity sensor element  22   a , whereby the humidity in the air A indicative of moisture in the structure  12  may be measured using the humidity sensor. The adhesive means  44 /continuous area may act as a seal between the ambient air  58  and the hole  52  in the structure  12 , which in turn provides for a more accurate measurement. 
     A method for measuring humidity indicative of moisture in the structure  12  may (hence) comprise: providing the measuring device  10  (S 1  in  FIG.  5   ), wherein the tubular element  30  of the measuring device  10  is arranged in the hole  52  of the structure  12 , and wherein the housing  14  of the measuring device  10  is positioned on the surface  54  of the structure  12  surrounding said hole  52  and exposed to ambient air  58 , except the flat underside  16  of the housing  14  facing the surface  54 ; and measuring humidity (S 2 ) indicative of moisture in the structure  12  using the humidity sensor  22   a - b , while the tubular element  32  is arranged in the hole  52  and while the housing  14  is positioned on the surface  54  and exposed to the ambient air  58 , except the flat underside  16 . 
       FIG.  6    illustrates a system  60  comprising a plurality of measuring devices  10  of the type described above. The system  60  is installed in a recreational vehicle  62 . The measuring devices  10  may for example be mounted on the floor  64 , in the walls  66 , and in the ceiling  68  of the recreational vehicle  62 . In the illustrated embodiment, the system  60  comprises twelve measuring devices  10 , but it could comprise more or fewer measuring devices  10 . 
     The measuring devices  10  may be installed then the recreational vehicle  62  is manufactured, or they could be retrofitted to an existing recreational vehicle  62 . A measuring device  10  may be installed by drilling a suitable hole  52  in the structure (floor, wall, ceiling) to be measured, then a protection of the double sided foam tape adhesive means  44  is peeled off, and then the tubular element  30  is inserted into the hole  52  until the housing  14  is stopped by the surface  54  and the measuring devices  10  is secured to the structure in questions by the double sided foam tape adhesive means  44 . Since the measuring devices  10  are battery driven and communicate wirelessly, no wiring is needed. 
     The system  60  further comprises a remote apparatus  70  in the form of a modem. The modem  70  may be paired with the measuring devices  10 . The modem  70  is adapted to receive measurement data wirelessly from the plurality of devices  10  sent by the wireless communication means  26 , and to transmit the received measurement data wirelessly to a server  72 . The modem  70  may be a mobile broadband modem (wireless modem), for example based on 5G. The modem  70  is also installed in the recreational vehicle  62 . 
     The server  72  may be adapted to receive the measurement data transmitted by the modem  70 , and to detect if a water leak has occurred in the recreational vehicle  62 . 
     In use, the devices  10  continuously or repeatable measure relative humidity in the floor  64 , walls  66 , and ceiling  68  of the recreational vehicle  62 , and transmits the measurement data to the modem  70 , which relays the measurement data to the server  72 . The (twelve) devices  10  may for example measure the relative humidity once every second day. 
     Except relative humidity data, the measurement data can include temperature data provided by the temperature sensor  27  in each device  10 . Furthermore, the measurement data may be accompanied by a device identifier and a time stamp. Hence an exemplary data transmission from one of the devices  10  could be device identifier = lD1, time stamp = 2020-03-17 11:06, relative humidity data (=measured (relative) humidity) = 35 RH%, and temperature data = 17° C. 
     The server  72  detects if a water leak has occurred in the recreational vehicle  62  based on the relative humidity data in the received measurement data. The server  72  may for example detect (estimate) that a water leak has occurred in the ceiling  68  of the recreational vehicle  62  if the relative humidity data in the measurement data from at least one measuring device mounted to the ceiling  68  exceeds a first threshold. The first threshold may for example be set in the range of 60-80% RH. 
     To improve the accuracy of the water leak detection, the server  72  may take into account natural fluctuations in humidity by comparing the relative humidity data of each device  10  to an average of the relative humidity data of all the devices  10  and/or the ambient air humidity (measured e.g. by a conventional hygrometer; not shown) at a given time. For example, if the relative humidity measured by one of the devices  10  increases from one time t1 to another t2 from say 20% RH to 65% RH, generally indicating a water leak, it may be that the later measurement at t2 does not deviate significantly from the average measured relative humidity (e.g. 60% RH) at that time t2 because of more humid weather, whereby server  72  may refrain from detecting that a water leak has occurred. In another example, if the relative humidity measured by one of the devices  10  is constant (e.g. about 40% RH) from one time t1 to another t2, generally indicating no water leak, it may be that the later measurement at t2 is significantly higher than the average measured relative humidity (e.g. 15% RH) at that time t2, which average has decreased because of dryer weather, whereby the server  72  nevertheless may detect that a water leak has occurred. 
     The server  72  may also detect a water leak or (potential) moisture damage in the recreational vehicle  62  taking into account at least one dew point calculated based on the relative humidity data and the temperature data in the received measurement data. Dew point may be defined as the temperature at which a vapor (such as water) begins or would begin to condense. The server  72  may for example detect potential moisture damage if the temperature of the temperature data is below the calculated dew point, but not if the temperature of the temperature data is above the calculated dew point for the same measured relative humidity value. 
     The server  72  may further issue, or cause issuance of, an alarm if the server  72  detects that a water leak or moisture damage has occurred in the recreational vehicle  62 . The alarm may for example be issued as a message (e.g. e-mail and/or SMS) or notification to a smartphone  74  or the like of the owner  76  of the recreational vehicle  62 . 
     The server  72  may further issue, or cause issuance of, a warning to the owner  72  if the relative humidity data in the measurement data of at least one of the devices  10  exceeds a second, lower threshold. The second, lower threshold could be set in the range of 40-60% RH, for example. 
     The person skilled in the art realizes that the present invention by no means is limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the humidity sensor element  22   a  could alternatively be placed a short distance into the channel of the tubular element.