CM-3 Rebar Continuity Tester

The CM-3 verifies electrical continuity directly by measuring resistance with a relatively large current (0.5 Amp) through a rebar connection for 0.5 seconds.

When using Cathodic Protection to stop corrosion on steel reinforcement in concrete, it is extremely important that all the steel rebar are electrically continuous.

Unconnected rebar will not be protected and are likely to corrode.

When the rebars are connected, we say that they are in electrical continuity.

Operation

In addition to verifying that the resistance is below 1 Ohm (ref. ISO 126969) the CM-3 also verifies the continuity check, confirming the residual voltage between the test points falls to 0 within 100 ms after the resistance measurement is complete.

A common Digital Multi Meter [DMM] is not a reliable instrument to verify reinforcement continuity. Concrete can be seen as a “solid electrolyte” that will generate its own small potentials. A DMM uses very small currents to measure resistance and can be influenced by the concrete potentials. The alternative and indirect method of measuring potentials between the rebars with a DMM is better and almost certain to give valid results.

CM-3 can remove the “almost” by using a current that may be as much as 1000 times higher than a DMM. The test current applied by the CM-3 is also more in line with the level of currents that must be expected though the rebars from an ICCP installation.

Specifications

A probe for easy rebar contact is supplied with the CM-2. The Probe is a spring loaded punch style contact that can penetrate surface rust. 

The instrument and the probe accepts common 4 mm banana connectors, cable is not included. Resistance in measurement cables may easily be eliminated through the CM-2's calibration feature.