Cancellation Loops

To cover large areas, compensate for the effects of metal and or control spill, a range of different induction loop configurartions can be used. The choices are Cancellation Loop, Figure 8 loop™,, Super 8 Loop™ and Univox SuperLoop ^series®.

A cancellation loop is a simple and cost effective way of controlling the spill field in 1 or 2 directions. In its simplest form, it is a figure 8 loop where the ratio of the 2 areas circumscribed by the cable are such that the magnetic fields extending beyond the loop in 1 direction cancel, as shown in the diagram. This design is simple to install and relatively low cost using just 1 induction loop amplifier. However, the cancellation loop must be installed in the room so not all of the space in the room will be covered to standard.

Installing a cancellation loop along a second side of the room will reduce the area coverage in the room further, but in some circumstances, it is still preferable to using Univox SuperLoopSeries^® technology.

The exact induction loop area ratios to achieve optimum cancellation of magnetic field can be found by trial and error or by using a software based design tool. Cancellation loops can also be designed using an antiphase Super 8 (+-)loop or by driving 2 independent loops with different current values, either by using 2 separate induction loop amplifiers or a custom designed ratio transformer.