TCL and eltcl? Cdnext and CMRL?

2022 year 4 month 8 Japan , A customer calls to inquire about using DSX2-8000 When choosing test standards “+PoE” and “+All” Options , I don't know the difference between the standard without this symbol and the ordinary standard ？ I have to mention that , This is the same as before DTX series , such as DTX-1800, The difference between the test results , The following items are more than traditional test parameters ：

1.TCL( Transverse conversion loss );

2.ELTCL（ Transverse conversion transmission loss ）;

3.CDNEXT（ Common mode to differential mode near end crosstalk ）;

4.CMRL（ Common mode return loss ）.

 

 

 

Let's talk about fluke cable certification tester in detail . When testing twisted pair wiring , Some key parameters need to be set on the tester to test that the permanent link meets the industry standard parameters , Such as Insertion loss 、NEXT、PSNEXT、ACR-N、PSACR-N、ACR-F、PSACR-F And return loss . In the test Cat 6A（ or ISO11801 The standard Fa class ） when , We also use PSANEXT（ Integrated external near end crosstalk ） and PSAACR-F（ Integrated external far end crosstalk ） Conduct external Crosstalk Test .

Although the required parameters will be automatically tested according to the test limits you choose , But have you noticed the of fluke network DSX There are （+All） Suffix series test this option , Want to know what this means , Why and when should I choose it ？

Fluke DSX The latest version of series tester 6.1 Simplified identification of limits , And in many TIA and ISO The bottom of the limit provides “+PoE” and “+All” Options . If these are not checked , Then only the field test limit is displayed . Choose them , The list will follow “（+PoE）”“（+All）” The measured value of the version is added to the list and becomes longer .

When you choose with （+PoE） or （+All） When testing the suffix , You are actually adding ANSI/TIA or ISO/IEC Other test parameters not required for field testing . about “+PoE”, These measurements are internal DC resistance imbalance and inter pair DC resistance imbalance , And the limit value of DC loop resistance .”+“ all ” Including these and ELTCTL、TCL、CMRL and CDNEXT Measured value . Although field tests do not require these additional measurements , But manufacturers need many of these parameters to establish compliance , This is why you will find them listed on the wiring specification sheet .

Although for certification purposes , You may not need to test these limits , And they do increase your testing time slightly , But they can provide you with more information about the performance of cabling equipment . Let's take a closer look , To help you decide whether to choose （+PoE） or （+All）.

TCL and ELTCL
Ethernet signals are used in differential mode , Noise signal is applied to common mode . When noise is injected into the cable , Part of the common mode signal can be converted into differential mode , And become part of the Ethernet signal . This phenomenon, called mode switching, is not a good thing for Ethernet signals .
TCL（ Transverse conversion loss ） and TCTL（ Transverse conversion transmission loss ） Are two parameters for measuring mode conversion .TCL Measure the mode conversion of one end to the inside ,TCTL Measure the mode conversion inside the other end . However , because TCTL The common mode semaphore under test depends on the link length caused by insertion loss , So you have to use ELTCTL（ Isoelectric level TCTL） Balance .
TCL and ELTCTL Only about 6 Second test time , They are excellent indicators of noise immunity and whether cable links can provide sufficient performance in a noisy environment , Including external crosstalk from adjacent cables or from other external sources （ Such as noise in industrial environment ）. therefore , If you install in a noisy environment , And a simple method is needed to determine the noise resistance , Then you may need to choose （+All）. Besides , It can reassure you in the manufacturer's statement , And it is an ideal choice for troubleshooting – fault TCL and ELTCTL It may cause bit error and retransmission , Even if other required transmission parameters provide a good margin above the standard limit .

CDNEXT and CMRL
CDNEXT（ Common mode to differential mode near end crosstalk ） Is a parameter for troubleshooting only , The manufacturer does not need this parameter , And in TIA or ISO/IEC There is no test limitation specified in the standard . However ,TSB-1197“ Mode conversion parameters of balanced twisted pair wiring ” This is mentioned in , To help wiring professionals better understand the impact of noise on twisted pair wiring , Including external crosstalk and other external sources .
CDNEXT Is the difference between the common mode voltage and the differential mode voltage applied to a pair .
Voltage measured on other pairs at the same end of the cable . better CDNEXT Value corresponds to better noise immunity and lower emission . because CDNEXT It mainly appears in the connection hardware , So bad CDNEXT It's mainly about connector selection , May indicate low quality . It's unlikely that , But it may also be a process problem .
CMRL（ Common mode return loss ） Is the difference between the common mode signal power applied to the pair and the reflected common mode signal power . These signal reflections are caused by changes in cable impedance , It may only be worthwhile to support transmission speeds that exceed 10 Gig Analysis of cabling equipment , Although the manufacturer did not require , There is no test limit specified in the industry standard
Now? , You've got it DSX Series examples DSX2-5000 CH DSX2-8000 CH On the tester （+PoE） and （+All） The meaning of the suffix , You can decide whether to add these measurements .

I hope a little simple introduction , Can help you .