Planar Field Antenna: Construction Details
Planar Field Antenna – The concepts associated with planar field antenna design (reinforcing fields and grounded shields, specifically) are introduced in the Antenna Design Overview. We recommend that you familiarize yourself with these concepts before you attempt to construct your planar field antenna.
Antenna Construction – The antenna should be rectangular in shape and may be constructed of ½” or ¾” tubing or ½” flat stock – copper, steel or aluminum are the preferred materials, but any rigid conductor is usable. Cut the material to the desired lengths and either weld the corners or solder them together with copper elbow fittings. The maximum length for the narrowest dimension is limited to thirty-six inches (91.6 cm).
Insulator Construction – Use the illustration as a guideline for making your insulators. They should be made from PVC or nylon bar stock that is one inch (2.54 cm) in diameter. They should be two inches (5.09 cm) in length, with holes top and bottom – tapped for 5/16″-18 screws. The bottoms of the tapped holes must be at least one inch (2.54 cm) apart.
Antenna/Insulator Assembly – Drill clearance holes through the antenna, in the configuration shown in the illustration, and fasten the insulators to the antenna with the appropriate length screws and lockwashers. A minimum of eight insulators must be used, but the number and the span between insulators will vary with the materials used for the antenna element – rigidity is the controlling factor.
Grounded Shield Construction – The grounded shield should be constructed of two inch (5.09 cm) wide and eighth inch (.32 cm) thick steel or aluminum flat stock.
Measure the width of the antenna/insulator assembly to the outside edges of the insulators and cut two pieces of the shield material to this length. Then, make a measurement of the height and add two times the thickness of the shield material to the measurement. Now, cut two pieces of the shield material to this length. Weld the corners of the shield sections – corner braces may be used for added strength.
Antenna/Shield Assembly – Place the shield around the antenna/insulator assembly to insure that it fits properly. Then, make measurements for mounting the shield to the insulators. Drill clearance holes through the shield and fasten the shield to the insulators with the proper length screws and lockwashers.
Antenna/Coupler Assembly – Drill clearance holes through the antenna (refer to the 02A558 Coupler illustration below to determine the size and spacing of the holes) and fasten the coupler to the antenna with the hardware provided with the unit. You must sand the area of the tubing where the coupler contact plate meets it, to expose bare, clean metal and insure good electrical contact. Dress the coupler cable so that it exits the coupler perpendicular to the antenna. The cable must not be routed along or attached to the antenna element.
Planar Field Antenna Installation – To determine the proper mounting distance for your antenna, as mandated by OSHA regulation, refer to the PC1000 Antenna Design Overview (Formula for Calculating Minimum Safety Distance).
Secure the Planar Field Antenna to the machine. The antenna must be firmly mounted and incapable of movement in any direction. Machine parts or fixtures must not extend inward past the plane of the grounded shield, as this can result in a reduction in field sensitivity.
Attach a copper ground wire to the shield and connect the other end to the machine control ground.
Now, you must refer to the Installation section of the PC1000 User’s Manual and follow the procedures to complete your installation. You must also complete all the test procedures in the Operation section of the PC1000 User’s Manual.
As a final word of caution, grounded shields may create a situation where a person can reach around the outside of the shield to a pinch point. If this is the case in your application, you must provide a means of guarding the accessible pinch points. In the types of applications where planar field antennas are employed, that usually means installation of fixed barrier guards.
Please read the manual carefully before attempting an actual installation.