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What are the performance indicators of twisted pair power cords (1)

Update:17-04-2020
Summary:

(1) Attenuation Attenuation is a measure of signal loss […]

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(1) Attenuation
Attenuation is a measure of signal loss along the link. The attenuation is related to the length of the power cable. As the length increases, the signal attenuation also increases. The unit of attenuation is "db", which represents the ratio of the signal strength at the source transmitting end to the signal strength at the receiving end. Since the attenuation varies with frequency, the attenuation at all frequencies in the application range should be measured.
2) Near-end crosstalk
Crosstalk is divided into near-end crosstalk and far-end crosstalk (FEXT). The tester mainly measures NEXT. Due to line loss, the effect of FEXT magnitude is small. Near-end crosstalk (NEXT) loss measures the signal coupling from one pair of wires to another pair of wires in a UTP link. For UTP links, NEXT is a key performance indicator and the most difficult to accurately measure. As the signal frequency increases, the difficulty of its measurement will increase. NEXT does not indicate the crosstalk value generated at the near endpoint, it only indicates the crosstalk value measured at the near endpoint. This value will vary with the length of the cable, the longer the cable, the smaller the value becomes. At the same time, the signal at the sending end will also be attenuated, and the crosstalk to other pairs will be relatively small. Experiments show that only NEXT measured within 40 meters is more real. If the other end is an information socket farther than 40 meters, it will produce a certain degree of crosstalk, but the tester may not be able to measure this crosstalk value. Therefore, it is best to perform NEXT measurements at both endpoints. The tester is equipped with corresponding equipment, so that the NEXT value at both ends can be measured at one end of the link.
(3) DC resistance
TSB67 does not have this parameter. The DC loop resistance consumes part of the signal and converts it into heat. It refers to the sum of the resistance of a pair of conductors. The DC resistance of the twisted pair of 11801 specifications shall not be greater than 19.2 ohms. The difference between each pair should not be too large (less than 0.1 ohm), otherwise it indicates poor contact and the connection point must be checked.