An IR Free Potential is a potential measured at the exact point where the surface of the structure meets the surrounding environment. A potential measurement at this point is not distorted by the soil resistance between reference electrode and the structure's surface.
IR-Free Stationary Reference Probe
The "Stelth7" IR-Free reference probe is designed to provide an IR Free Potential reading that is as close as theoretically possible to that point where the structure and environment meet. This is achieved by combining into a "PROBE" the proven Stelth technology and a precision mild steel coupon which, when placed in the same soil conditions as the structure, will be exposed to the identical forces acting upon this structure's flaws or holidays (exposed areas) such as the cathodic protection system, stray currents and environmental conditions.
How to set-up and measure with the "Stelth 7" probe
The "Stelth7" probe is connected to your structure through a test station. Two wires are connected to the structure and are brought into the test station and connected to terminals four and five. Two wires connected to the steel coupon in the probe are brought into the test station and connected to terminals one and two. The third wire connected to the reference electrode in the probe is brought into the test station and connected to terminal three. A shunt is placed across terminals one and four Your potential reading is taken across terminals two and three.