To understand how to determine whether a PoE switch is powered by standard PoE, you must first figure out what a POE switch is.
A PoE power supply switch refers to a switch capable of providing network power to a remote power receiving terminal through a network cable, and includes two functions of a network switch and PoE power supply. It is a relatively common power supply device in a PoE power supply system.
Classification of POE switches
1.Standard POE switch
Complying with IEEE802.3af and 802.3at standards, it is a standard POE switch (commonly known as 48V). The complete POE includes power supply equipment (PSE, Power Sourcing Equipment) and power receiving equipment (PD, Power Device). The poe switch is PSE A kind of equipment. PSE is a device that supplies power to the terminal and is also the manager of the POE Ethernet power supply process. PD is a terminal device that accepts power (48V national standard equipment contains PD chips).
2. Two types of non-standard POE switches.
On the contrary, it is a non-standard POE switch ("non-standard" for short, "non-standard" is commonly called 24V, but non-standard is 48V, 24V, 12V, 5V, etc.).
Main application areas of POE switches
The POE switch mainly provides the network and power for monitoring (powering the camera), wireless coverage (powering the AP), and wireless transmission (powering the bridge).
Working process of standard POE power supply switch
1. Detection: The poe switch first outputs a small voltage, and detects that it contains a power receiving device that supports the IEEE802.3at / af standard chip (supporting the IEEE802.3at / af standard chip for short "PD").
2. PD classification: After detecting PD, the poe switch classifies the PD device and evaluates the power of the PD device.
3. Power supply: During the startup period (usually less than 15 μs), the poe switch supplies power to the PD from a low voltage until the voltage required by the PD is sufficient to supply stable and reliable DC power to the PD equipment.
4. Power failure: If the PD device is disconnected, the poe switch will stop powering the PD quickly (usually within 300-400ms), and repeat the detection process to detect whether the terminal of the cable is connected to the PD device.
Multimeter test method for true and false POE
Start the device, adjust the multimeter to the voltage measurement position, and use the two multimeter pens to touch the PSE device power pin (usually 1/2, 3/6 or 4/5, 7/8 of the RJ45 port) ), If a device with a stable output of 48V or other voltage values ​​(12V, 24V, etc.) is measured, it is a non-standard product. Because in this process, the PSE does not detect the power receiving equipment (here, the multimeter), and directly uses 48V or other voltage values ​​to supply power.
Conversely, if the voltage cannot be measured, the multimeter's needle jumps between 2 and 10V, which is standard PoE. Because at this stage, the PSE is detecting the PD end (here is the multimeter), and the multimeter is not a legitimate PD. The PSE will not supply power and no stable voltage will be generated.
After mastering the above judgment methods, you can distinguish whether a PoE switch is powered by standard PoE.
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