The vast majority of RF survey instruments are comprised of two major components:

A broadband probe—the sensor

A meter

Most probes are isotropic, or omnidirectional. Isotropic probes are designed with a set of three identical sensors placed at 54.7° off the center axis of the probe. This geometric arrangement is designed to yield the same results from all directions. In reality, a good probe design yields very similar results in most directions, with the direction of the handle being a notable exception.

Although there are a few anisotropic (directional) probes on the market, they are of little value except to find leaks. Microwave oven instruments use anisotropic probes because the regulations for microwave ovens are emissions standards, not human exposure standards.

There are a couple of special designs where the sensor and probe are built into the same package, but this approach is rare because it results in a dedicated system with limited flexibility.