What are the specifications of the power cord

A power line is a wire that transmits current. Generally, the mode of current transmission is point-to-point transmission. Power line can be divided into AC power line and DC power line according to the purpose. AC power line is usually made of high voltage AC wire. This kind of wire needs unified standard to obtain safety certification before it can be formally produced. The DC line is basically through low voltage DC, so the safety requirements are not as strict as AC line, but for the sake of safety, countries still require unified safety certification.

Performance index of twisted pair in power line

For twisted pair, users are most concerned about the performance indicators. These indexes include attenuation, near end crosstalk, impedance characteristics, distributed capacitance, DC resistance, etc.

(1) Attenuation

Attenuation is a measure of signal loss along the link. The attenuation is related to the length of the cable. With the increase of the length, the signal attenuation also increases. Attenuation is expressed in dB, which is the ratio of signal strength from the source transmitter to the receiver. Since the attenuation varies with frequency, the attenuation should be measured at all frequencies within the application range.

(2) Near end crosstalk

Crosstalk can be divided into near end crosstalk and far end crosstalk (FEXT). The tester mainly measures next. Due to the existence of line loss, the value of FEXT has little influence. Near end crosstalk (next) loss is the measurement of signal coupling from one pair of wires to another in a UTP link. For UTP link, next is not only a key performance index, but also the most difficult index to accurately measure. With the increase of signal frequency, the difficulty of measurement will increase. Next does not represent the crosstalk value generated at the near end, it just represents the crosstalk value measured at the near end. This value varies with the length of the cable. The longer the cable is, the smaller the value becomes. At the same time, the signal at the transmitter will be attenuated and the crosstalk to other wire pairs will be relatively small. Experiments show that only the next measured within 40 meters is true. If the other end is a 40 meter information socket, 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 make next measurements at both endpoints. Now the tester is equipped with corresponding equipment, so that the next value of 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's the sum of the resistances of a pair of wires,

The DC resistance of 11801 twisted pair shall not be greater than 19.2 ohm. 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.

(4) Characteristic impedance

Different from loop DC resistance, characteristic impedance includes resistance, inductance impedance and capacitance impedance with frequency of 1-100mhz. It is related to the distance between a pair of wires and the electrical performance of insulators.

Various cables have different characteristic impedances, while twisted pair cables have 100 ohm, 120 ohm and 150 ohm.

(5) Attenuated crosstalk ratio (ACR)

In some frequency ranges, the proportional relationship between crosstalk and attenuation is another important parameter to reflect the performance of cable. ACR is sometimes expressed as signal-to-noise ratio (SNR),

It is calculated by the difference between the worst attenuation and the next value. Larger ACR value indicates stronger anti-interference ability. Generally, the system requires at least 10 dB.

(6) Cable characteristics

The quality of a communication channel is described by its cable characteristics. SNR is a measure of data signal strength considering interference signal. If the SNR is too low,

When the data signal is received, the receiver can not distinguish the data signal from the noise signal, resulting in data error. Therefore, in order to limit data errors to a certain range,