Educational Articles

Don’t get caught short in your reverse loop design!

Limit your liability! Don’t let your installer get caught short in their reverse loop design.

BD Loops has larger sizes available, standard sizes up to 52 feet (6’ x 20’).
Depending on the application custom loops sizes available up to 132 feet (6’ x 60’).

Why specify a larger loop size?

Below is an example of what could result from this type of compromise:

Any loop providing the function of reverse/obstruction/safety or close needs to span the full driveway width coming within 2ft from the curbs on each side. If you leave a gap larger than 2ft on each side of the loop from the curb a small vehicle or motorcyclist will be able to pass by without being detected if they drive near the side. Which is likely to happen, especially if the motorcyclist is driving close to the curb because they are planning on turning left or right after passing through the gate, or if a telephone entry system that is used to open the gate is located on the far left (or right, in some countries) side.

Many installers are taught that if a loop’s detection height or field will extend around the loop in all directions. This causes installers to install loops up to 4 – 4.5ft away from the curbs or side of the roadway.

This simply isn’t true. The detectable field that a loop generates is an electromagnetic field. This field will behave like a magnet.  This rough diagram below shows the direction that current is flowing in this loop.

The loop legs are labeled: North, South, East, and West. 

When you look at the diagram you can see that the current is flowing in opposite directions for the N & S and the E & W legs of the loop. Because the current is flowing in opposite directions, the EM Fields that are being generated act like magnets and attract (opposites attract) and pull the fields in towards the opposite legs. This is why the usable detection fields that surround outside of the loop only extend for a few inches beyond the outside perimeter of the loop. This attraction effect is also the reason why the detection field height of a loop increases as the short leg of the loop gets longer. For example if you install a loop with a 2ft short leg, the N and S sides of the loop are closer together, which means the magnetic attraction is stronger, which is why the fields stand lower. If a loop has a 6ft short leg the N & S sides are further apart, and the attraction is weaker, which is why the detection fields stand taller.

The detection fields are mostly concentrated above and below the loop because of this magnetic attraction. This is why loops need to span the full driveway width to be within 2ft of the curbs or side of the roadway. Protect the gate path, and limit your liability, do not install a loop that is too small to protect the gate path!

If you have any questions about loop layout design please give us a call: 714-723-0946

BD Loops

The Loop Experts!

BD Loops was founded in 2001. Their preformed loops and accessories are designed with the installer in mind. BD Loops offers a complete loop system solution including preformed direct burial loops, preformed saw-cut loops, loop sealant, blades, testing devices, and installation tools. BD Loops has a reputation for reliability and ease of installation. They pride themselves on the quality of their products and their commitment to providing excellent customer service and support. BD Loops preformed loops are made in the USA at their facility in Placentia, CA.