|Despite the standards permitting marginal passes, some customers want to know if any of the measurements were marginal immediately after the AUTOTEST has finished. |
When we talk about a result being marginal, we are referring to the results falling within the accuracy of the field tester. When the result is marginal, the standards require us to report the result with an asterisk (*). This cannot be turned off.
In the SETUP you will find TOP LEVEL PASS * INDICATION:
If you enable this, an asterisk will appear on the summary screen at the end of the AUTOEST, as shown below:
This does not necessary indicate that NEXT was marginal. Its highlighting that one of the measurements was found to be marginal. In this case it was Return Loss.
Here we see that the result is marginal for Pair 3,6 on Return Loss. Even if you disable TOP LEVEL PASS * INDICATION, this asterisk will remain here and on the test report as required by the standards.
We are aware that the Agilent Wirescope 350 and Ideal Industries LANTEK 6/7 permit you to disable the asterisk. Although the standards do not allow this, the feature is added as a benefit to the installer but at the cost to the end user.
If the TOP LEVEL PASS * INDICATION is enabled, and one of the measurements is found to be marginal, the analyzer will automatically run the diagnostics to determine the source. By pressing FAULT INFO, you can see where improvements can be made if desired.
Standards dictate that any marginal passes are considered the same as a pass and therefore compliant.
What the standards dictate (In detail)
ANSI/TIA-1152 which supports category 5e, 6 an 6A installations states in section 4.2.4 Pass/Fail results.
A pass or fail result for each parameter shall be determined by the specified limits for that parameter. The test result of a parameter shall be marked with an asterisk (*) when the result is closer to the test limit than the measurement accuracy published by the field tester manufacturer for the permanent link and channel. Refer to clause 4.4 for detailed information on measurement accuracy requirements. The field test manufacturer shall provide documentation as an aid to interpret results marked with asterisks. An overall pass or fail condition shall be determined by the results of the required individual tests. Any fail or fail* shall result in an overall fail. In order to achieve an overall pass condition, all individual results shall be pass or pass*.
Figure 1. Accuracy Region
IEC61935-1 which supports both ISO/IEC 11801 and EN 50173 Class D & E systems states in 5.4 Data reporting and accuracy 5.4.1 General - A Pass or Fail result for each parameter shall be determined by the allowable limits for that parameter. The test result of a parameter shall be marked with an asterisk (*) when the result is closer to the test limit than the measurement accuracy for the permanent link or channel
The graph (Figure 1.) shows an example of an equipment tolerance region around a NEXT pass/fail test limit. The red lines above and below the test limit are offset by a dB value equal to the specified instrument accuracy. If the measurement falls within the region below the limit, the measurement is marked with a Fail*. If the measurement falls within the region above the test limit, the measurement is marked with a Pass*. An overall Pass or Fail condition shall be determined by the results of the required individual tests. Any Fail or Fail* shall result in an overall Fail. In order to achieve an overall Pass condition, all individual results shall be Pass or Pass*.
Operating Procedures to avoid unnecessary costs
The contractor can take several precautionary measures that avoid high and unexpected costs related to marginal pass test results at the end of the project.
All technicians involved with the installation should be trained and should be knowledgeable about the installation procedures and practices to avoid workmanship problems. They must be held to execute their tasks in full compliance with the recommended tools and utilizing the approved practices.
Test equipment Accuracy
Select a tester that is repeatable, accurate and fully complies with the applicable industry standards. One way to assure your-self that a tester meets the standards in all aspects is to look for an independent certification of the tester. For instance, the Fluke Networks DSP- 4000, DSP-4100 and DSP-4300 have been independently certified by Underwriters Laboratories (UL). They independently certify that these testers exceed the TIA/EIA Level III accuracy specifications. The newest member of the product family the DSP-4300 is scheduled to undergo this independent certification in the very near future.
Some tester manufacturers allow you to manually disable the * to hide marginal results. Disabling the * makes the test(er) non-compliant. This disabling feature is NOT possible within the DSP-4000 Series CableAnalyzers. Hiding marginal results only puts your reputation and business at risk, so why do it? The best thing you can do is select a tester with exceptional accuracy to minimize or eliminate marginal results.
Test equipment Interface adapter cables
Tester interface cables are a very significant component in the accuracy and reliability of the test results especially for the Return Loss parameter. A worn interface cable contributes itself in a very significant way to the measured Return Loss value of the link-under-test. The definition of the Permanent Link model in all the industry standards specifies that tester interface cabling cannot contribute in any way to the test results. In order to be compliant with this requirement, contracts should specify that the installation shall be tested using the Permanent Link test standard with the appropriate tester interface adapters. The Fluke Networks DSP-LIA101S permanent link interface adapters far exceed the standards requirements.
Test equipment - Diagnostics
Another significant time saving characteristic of the tester is its ability to identify the location of a possible defect that causes the link to produce a marginal test result. The DSP-4000 Series testers can be configured in the SET UP menu to report the result of the Autotest with a Pass* if any one test parameter yields a Pass* result. In this configuration of the test tool when a Pass* Autotest result appears, the technician presses the FAULT INFO button to learn which parameter(s) produced a marginal pass result as well as the wire pair or wire pair combination. In addition, the DSP Series testers identify the location of each defect in a graphical format measured in meters or feet from the main test unit. This diagnostic report allows the technician to identify a marginal connector, a suspect termination or whether the cable itself is the source of the marginal performance. Obtaining this diagnostic information immediately upon completion of the certification test (Autotest) allows the installation team to identify the problem, execute the corrective action and retest. This immediate resolution saves time and costs.
If the end-user is expected to receive a warranty from the premise-wiring manufacturer, the contractor should be fully aware of the warranty criteria and conditions. For instance, if the warranty program states that marginal passes are not accepted for any of the test parameters, the contractor may want to construct some sample or trial-links and verify that the technicians obtain good results with the hardware components obtained through the distribution channel.
Lastly, the statement of work for the project, agreed to by all parties involved before any work commences, should clearly set all expectations with regard to the test procedure, the industry test standard, the accepted field test equipment, and the format for the deliverable test results.