The continuity test (also called low resistance measurement) is measuring the low resistance of cables, from 1 mΩ to 250 Ω.
The continuity test can be made in 2 or 4 wires according to the resistance to be measured : 2 wires for resistances > 1 Ω, and
4 wires for resistances < 1 Ω.
The continuity test in 2 wires mode consists in injecting a programmable current and measuring voltage and current at the terminals of the resistance to be tested. Ohm's law will give the exact value.
The continuity test in 4 wires mode (Kelvin method) divides the switching matrix into two internal buses, the first directing the test current, the second conveying the voltage of the terminals of the element under measurement. Even-addressed points are allocated to the SENSE of the measurement, odd points to injection of the current. This arrangement is possible throughout the switching matrix and can be combined with 2-wire continuity tests (see appendix).
To give you an example, the continuity test in 4 wires mode lets you carry out measurements on wires of 50 cm length and 5/10 mm cross-section (between 7 and 13 mW) with good resolution.