The DT Wireless Sensor is easy to reliably attach at the desired location due to its low weight. It comes pre-mounted with a very thin self-adhesive Very High Bond (VHB) tape (3M F9460PC) that will work excellently for most common applications. The user only needs to remove the peel-off tape to expose the glue before attaching the DT Wireless Sensor to the surface.
The pre-mounted double-sided tape has a square opening in the middle, as shown in the picture, to allow using other types of glue without removing the tape in the few instances desired.
For best results, always start with a clean and dry surface. If required, clean the surface as by 3M in this application note. On the next pages, guidelines are given on how to attach the sensors under special conditions where the pre-mounted tape does not give the desired result. Special care should be taken for Temperature Sensors as discussed in the last section.
Trialing sensor location
A removable attachment may be desired for trialing placement of sensors. A clay glue is included in Disruptive Technologies Sensor and Starter Kits to enable impermanent installations. Apply a small piece of clay glue inside the center area at the backside of the DT Wireless Sensor or on top of the peel-off of the tape. This allows for using the pre-mounted double-sided tape at a later stage when the sensor location is confirmed. If additional clay glue is needed the below products are recommended.
Alternatively, a double-sided repositionable tape as suggested below can be used. In this case, attach the tape on top of the existing peel-off tape on the DT Wireless Sensor to save the original pre-mounted permanent tape for later use.
Mounting may require extra attention in some special cases. Below, guidelines for the following cases can be found
- Rough surfaces
- Permanent mount
- Cold environment
- Mounting Temperature Sensors
Inherently, thin tapes work best on smooth surfaces since there is little material to absorb unevenness. Thicker flexible foam tape is recommended for such applications. The following products can be suggested.
The pre-mounted tape on the DT Wireless Sensors is permanent VHB tape, and will in some instances damage the surface when removed. Even better adhesion can be achieved using glue to mount the sensors. The peel-off tape should be removed prior to gluing to allow the glue to attach to the double-sided tape in addition to the center area of the sensor without tape.
Note that the obtained strength in many cases is limited by the integrity of the surface. For example, the paint may come off the wall before the glue breaks. The following glues are tested on smooth surfaces with good results.
An alternative for rough surfaces is silicone-based glues. A glue giving some strength right after application makes assembly quicker. The following alternative is tested and found suitable.
Gluing to cold surfaces is challenging as most glues require temperatures around room temperature to cure. There are tapes that are designed for use at low temperatures. The two examples below from 3M can be used down to 0 deg C, and even below even though strength will be lower.
There is also a tape available from 3M suitable for use down to -20 deg C. This is meant for air sealing and is not double-sided, but it comes with a liner. However, the DT Wireless Sensor nodes can be glued to the top side of this tape using the pre-mounted tape. The liner can then be removed to expose the glue capable of assembly at -20 deg C. This is a relatively thin tape working best on smooth surfaces.
“Superglues” may also be suitable for use on cold surfaces. Good results were obtained with the following Loctite glue on both wood and metal kept is at -18 deg C.
Gluing to wet surfaces is challenging as most glues dissolve in water over time. But, there are tapes designed for use in wet environments, for instance, the two examples below from 3M. These tapes come in several widths, including 19mm, which perfectly fits the sensor. During installation in wet environments, make sure the surface is clean and dry. You can later remove the sensor using a sharp knife, fishing line, or a guitar string. Then, if the tape still is stuck to the surface, you can apply a citrus solution to the tape and let it work for a few minutes before rubbing off the glue. If you can not dry the surface before mounting, you can also use TEC7.
Mounting Temperature Sensors
The sensor will be thermally connected to the surface it is mounted on. The thin double-sided tape on the back of the sensor will attach the sensor close to the surface with a relatively low thermal resistance. Using the original tape will, therefore, result in a setup measuring mostly the surface temperature. In cases with a high thermal capacity of the surface (e.g. a concrete wall), the temperature response will be slow compared to the air temperature. In some cases measuring the surface temperature is desired. In other cases, the air temperature should be measured, and the sensor needs to be thermally insulated from the surface.
This can be achieved by using a thicker type of foam tape (e.g. Tesa 62612 or 3M VHB 4943F). However, in any case, a wall with high thermal capacity will impact the air temperature in the vicinity, so care must be taken to install sensors to measure what is desired. A good solution is to install multiple sensors to get an overview of the thermal dynamics of the total air volume and surfaces.
How to apply alternative tape on DT Wireless Sensors
Most double side tapes come in a width of 19 mm or ¾ inch (19.05 mm). The following should be done to assemble the tape:
- Cut a 19 mm length off the alternative tape
- Remove the peel-off-tape from the DT Wireless Sensor
- Attach the DT Wireless Sensor onto the glue side of the double-sided tape. This would ensure an excellent bond between the DT Wireless Sensor and the alternative tape
- Remove the peel-off-tape from the alternative tape when ready to attach the sensor
For large scale sensor mounting it is possible to buy pre-cut tapes from companies referred to as “converters”. These companies specialize in providing customized tape solutions on base products from tape manufacturers. Tape companies like 3M and Tesa have partner converters in each region. A recommended supplier for Europe would be Alfast in Denmark.
Removing tape from Sensor or wall
The best way to remove sensors from a surface is to lift it off with a thin sharp knife. Note that the surface and the sensor may be damaged depending on the strength of the surface. Use guidelines for trialing sensor location above if moving the sensor is desired.
Glue residues can best be removed by rubbing.
The advice can also be found in the following 3M guidelines