Contractors must know the truth and insider PoE power supply(2)

- Nov 14, 2017-

Question 5: how to choose PoE switch?

1. How Much Power Consumption Needs to Be Powered: PoE switches use different standards and have different output powers. For example, the IEEE802.3af maximum does not exceed 15.4W. Due to the loss of transmission wires, the maximum power consumption does not exceed 12.95W Powered by equipment. PoE switches conforming to the IEEE802.3at standard provide power to devices up to 25W.

2. How many devices can be powered by at most: An important indicator of a PoE switch is the total power of the PoE power supply. Under the IEEE802.3af standard, a 24-port PoE switch can provide 24 ports (370 / 15.4 = 24) when the total PoE power supply reaches 370 W. However, if the port has the largest single port according to the IEEE802.3at standard Power supply 30W calculation, at the same time, only up to 12 ports (370/30 = 12).

3. Need the number of interfaces, with or without optical fiber port, with no network management, speed (10/100 / 1000M).

Question 6: PoE power supply safe transmission distance? What is the choice of network cable?

PoE powered security transmission distance of 100 meters, so the proposed use of ultra-five copper cable within 100 meters. PoE power grid lines require this issue only in countries such as China rampant fake bargaining is a problem in many developed countries is not a problem. The PoE IEEE 802.3af standard requires the output power of the PSE output port to be 15.4W or 15.5W. The power received by the PD device after transmitting 100 meters must be no less than 12.95W. According to the calculation of the typical current value of 802.3af is 350ma, the resistance of the 100- (15.4-12.95W) / 350ma = 7 ohms or (15.5-12.95) / 350ma = 7.29 ohms. The standard cable is natural to meet this requirement, IEEE 802.3af poe power supply standard itself is determined by the standard cable. OPTFOCUS Monitoring Dedicated Data Cable The POE power supply function is applied to data cables for safe and long-distance transmission and power supply up to 300 meters. The reason why a PoE power supply network cable will be required is because many network cables in the market are non-standard network cables, which are not produced in strict accordance with the requirements of a standard network cable. The non-standard network cable materials are mainly copper clad steel, copper clad aluminum, copper clad iron, the resistance of these network lines, are not suitable for PoE power supply. PoE power supply must use the oxygen-free copper network cable, which is the standard network cable.

Previous:Under what circumstances need to use the PoE power supply module to power the camera Next:Contractors must know the truth and insider PoE power supply(1)