All installed cabling should be tested after installation is completed using a cabling certification tester, i.e. a tester that can perform all of the test procedures required within the cabling standards. Cabling verification testers, i.e. those that perform only a limited range of tests such as wiremap and length measurement, are not suitable for certifying the performance of newly installed cabling.
It is Important to be clear on which standard(s) the cabling is to be tested to. This will be defined within the project specification document or by the manufacturer of the cabling system that is offering an extended warranty.
Make sure that the test equipment is suitable for the testing to be carried out. Test equipment is defined within certain performance levels:
Typical test equipment used for testing up to Class EA/Cat 6A
Before commencing testing make sure that the test equipment is within the calibration timescales set by the test equipment manufacturer and that the test leads/heads are in good condition and within the maximum number of tests recommended by the test equipment manufacturer.
Make sure that the correct cable type and NVP are set for the cable under test. Some testers have a database of various manufacturers’ cables to be selected from but others may require manual setup. The NVP (Nominal Velocity of Propagation) is the speed that the electrical signal travels down the cable relative to the speed of light and is often expressed as a percentage. Setting the correct NVP is vital if the cable length measurements are to be correctly recorded.
Most manufacturers require the testing of the Permanent Link, i.e. the fixed, installed cabling between the patch panel and the consolidation point (CP) or work area outlet (WAO) if a CP is not present. Testing of the Channel, which includes the patch/equipment cords at each end is not recommended as the performance of the Channel will change each time the patch cords are changed.
If the cabling components are of good quality and the installation has been carried out within the specification guidelines then only ‘PASS’ test results should be seen. Star PASS or Star FAIL (*PASS/*FAIL) results are those where the margin of performance of the cabling system is within the test equipment’s limits of accuracy. These, together with FAIL results, will not generally be accepted by the manufacturer of the cabling system for warranty application purposes. Steps should be taken to determine the cause of the marginal PASS/FAIL or full FAIL and carry out remedial action to overcome the issue. As a rule of thumb, poor/FAIL results can be determined as follows:
NEXT - usually down to poor quality terminations such as cable pairs untwisted too much.
Return Loss (RL) - usually down to cable issues such as too many/too tight bends, excess
pulling force or over-tight cable ties.
Where available use the test equipment’s diagnostic tools to help locate causes of failures.
Save the test results using the outlet labelling convention for ease of tracing. Full test results, including graphs, should be saved in the test equipment’s native format, e.g. .flw for Fluke test equipment. Test results should be downloaded from the tester on a regular basis in order to minimise the risk of lost test results. Test results should be submitted to the cabling system manufacturer as part of the extended warranty application process, with electronic copies of the test results kept by both the client and the cabling installer for future reference.