Cable testing 101 question-and-answer series 】
Understanding of copper balance method
Cable testing 101 question-and-answer series 】
Understand copper balance method known as you may have heard of copper network cabling balanced twisted-pair copper wiring, maybe have you ever heard of a known as unbalanced dc resistance test parameters.
But all these balance related terms really mean?
Why to think of you?
Balance is the key electrical signals in two modes transfer -
Common mode and differential mode.
Differential mode is considered to be 'balanced' mode, the signal in each reference on two wire transfer, basically in the opposite force transmission.
Instead, common mode or unbalanced mode, the signal transmission at the same time, and as a reference.
Due to balance reference signal cables carry each other, they usually have symmetrical design, such as network the twisted-pair cable.
Unbalanced cables including those Shared a axis coaxial cable.
Understand the dc power supply and external power of electromagnetic noise to be common mode into the cable it is very important.
When the common-mode noise coupled to the perfect balance of the two wires twisted pair, the balance design can offset signal, the perturbation resistance implementation.
Balanced twisted-pair cable, however, has never been a 'perfect' balanced, this is we provide balance in accordance with the provisions of the standard of performance parameters.
PoE problem so now you understand the common mode (
And the difference (
Pattern differences, then we look at the power supply and Ethernet (
Applications via the twisted-pair wiring the relationship between the direct current transmission.
In 4 wire transmission power and data at the same time, in the application of the power supply to common mode voltage transmission, the voltage is the average distribution of the individual wires to the line.
This is the balance of another important effect.
If the line fully equal to the dc resistance of each wire in, is no difference in resistance.
This is to make average distribution of common-mode voltage.
Too much resistance difference can cause data signal distortion, which leads to the error, the retransmission even data link is invalid.
Also, it is impossible to realize perfect balance, and this is why we also offer the cause of the performance parameters of this type of balance.
The balance, then, produce have an adverse effect upon data signals of the cause of the imbalance is what?
Imbalance of the reason may be that bad work, termination and poor quality of cable.
Ensure more small bending radius and keep the twisted-pair cable as much as possible close to the end of the contact is the key to maintain balance.
In order to prevent PoE application of unbalanced dc resistance, solid conductor termination consistency is very important.
The overall quality of the cable and maintain appropriate physical geometry is also crucial for maintaining balance.
When poor quality of the cable diameter, concentricity,
, the weekly line of copper wires and the differences in terms of smoothness, there is a higher risk of imbalance.
Balance test when it comes to maintain proper balance to a greater degree to reduce the noise interference cable certification, schema transformation should be paid attention to.
Unbalanced cables, cable is injected in a model of common mode noise, lead to voltage and reduce the network performance, unequal will appear this kind of phenomenon.
Said the balance of two kinds of transformation parameters based on the standard model is the horizontal transmission loss (
And both ends of the equivalent lateral conversion loss (
, by injecting differential mode signal and then measuring line on the common mode signal to measure.
For these two parameters, the common mode signal is smaller, the better balance.
Test resistance is poor, should focus on dc resistance unbalance, industry standard specifies more dc resistance unbalance between the wires.
The line parameter validation for the two wire have equal enough resistance to achieve the effective support PoE common-mode current needs, and to avoid in the same line for transmission of data signal distortion.
Fortunately, DSX CableAnalyzer has the ability of measuring the difference and the common mode signal, which means that it can pass test mode conversion and unbalanced dc resistance test to verify the balance of the two types.
With data speed continuously improve, more and more transmission power and data at the same time, PoE equipment validation of balance is more important than ever before.
If you have any questions or problems, you are welcome to contact us at any time