The standard PoE power supply device has a PoE control chip inside, and has the function of detection before power supply. When the device is connected, the PoE power supply device will send a signal to the network to detect whether the terminal in the network supports PoE power supply PD device, and then provide the corresponding voltage and current according to the power required by the power receiving device.
The working principle of non-standard PoE power supply is to belong to the switching power supply class, no PoE chip, just through a transformer to turn 220V AC voltage down into low-voltage direct current, do not detect PD receiving equipment, directly in each RJ45 port uninterrupted output fixed voltage and current. Non-standard PoE products are strong power supply network cable power supply device, a power supply, there is no detection step, regardless of whether the terminal is PoE power supply equipment, if you can not determine the power and voltage of the power device, there will be a certain risk of burning.
1, look at the specification parameters, if the output voltage is not between 48-57V, then you can basically determine the non-target.
Each PoE power supply device will have a nameplate (below), whether it is PoE power supply, or PoE switch as long as the output voltage is not in the range of 48-57V, the common is 48V, basically determined to be non-target. Because the IEEE802.3AT /AF protocol stipulates that the standard PoE port output voltage range is between 48-57V, so this is known at a glance. However, if the output of the PoE power supply device is between 48-57V, it can not be judged that it must be the standard PoE power supply device, and it is necessary to use the simple test of the instrument to judge.
2，Use a multimeter to check the sequence of ports or network cables to test the voltage output of the network cables.
Start the device, adjust the multimeter to the voltage measurement gear, and touch the PoE power supply pin (usually 1/2,3/6 or 4/5,7/8 of the RJ45 port) with the two pens of the multimeter. If the device with 48V or other voltage values (12V, 24V, etc.) and stable output is measured, it is a non-standard PoE power supply device. Because in this process, the PoE power supply device does not detect the power device (here is a multimeter), and directly uses 48V or other voltage values for power supply.
On the contrary, if the voltage is not measured and the multimeter needle beats between 2 and 10V, it is standard PoE.
Because at this stage, the PoE power supply device is detecting the PD end (here is a multimeter), and the multimeter is not a legitimate PD device, the PoE power supply will not be powered, so a stable voltage cannot be detected. Engineering friends who have done monitoring and wireless engineering know that the reliability of engineering products is very important; The reliability is low, and the reliability of the whole system is lower, which not only affects the company's business development, but also increases the system maintenance cost to the engineering company greatly, and some can not even be accepted, resulting in serious losses.
Is non-standard PoE or standard POE selected in practical applications? This mainly depends on how many volts of input voltage the receiving device supports, as well as engineering cost considerations？
● The power receiving equipment requires the input voltage between 48-57V, especially the power of some power receiving equipment is variable, it is recommended to choose standard PoE power supply equipment, which is safer and more stable.
● The power equipment requires the input voltage between 48-57V, in fact, non-standard and positive PoE can be selected, according to the project cost, project requirements to decide.
● If the input voltage is not between 48-57V, the non-standard PoE power supply equipment can only be selected, and the non-standard cost will be lower. Before installation, we must understand the electrical parameters of the electric equipment.
