Ethernet cables include eight wires and should be configured as four unshielded twisted-pairs (UTP). Each pair is twisted together to cancel noise that can interfere with the data signal. These twisted-pairs provide a circuit path for network signals, as well as power for a PoE-enabled device. The cables are commonly available, and designated as Cat5, Cat5e, or Cat6.
Cat5 cables allow data transfer rates at 100 megabits per second (Mbps). A Cat5e cable provides data transfer rates at 1000 Mbps, which is equivalent to 1 Gigabit per second (Gbps). A Cat6 cable allows data transfer rates at 1-10 Gbps and has larger gauge wires, so the communication integrity is higher. The maximum length of any cable should not exceed 100 meters (328 feet), and they are backward compatible.
Simply stated, use the cable of your choice and connect it to the PD’s network port. PoE standards do not specify which wire pairs carry the specific polarity for the DC voltage. Consequently, if a connection has reverse polarity, the PoE-based equipment should have design elements to protect the circuitry.
Particle Measuring Systems’ Airnet® II and IsoAir Particle Sensors include circuitry that corrects for reverse polarity and assures the sensor receives the proper power requirements. The Airnet II power requirements are listed as a Class 0 device, which requires a small amount of current. The top right image shows an operational Airnet II operating on a PoE system. It requires only a vacuum line and a Cat5/5e/6 cable.
If a PoE-enabled PSE is not available, the Airnet II will require a PoE injector (PMS part number 1000015865) and a power cord (IEC 60320-1 Type C13). The power injector includes a status LED and can display three status conditions:
- Amber: Power On.The injector is connected to a wall outlet and is powered.
- Green: Power Active. A connected device is receiving power.
- Blink: Load Error. A connected device is not communicating with the network.
PoE is a simple, convenient method to build a network infrastructure that is flexible, efficient, and allows for future growth. As more devices connect to the PoE-enabled system, a PSE that provides more power may be required—but this option is much cheaper than installing new power outlets and network ports. In addition, a single UPS can provide reliable power and protect all devices connected to the system. Finally, since PDs like the Airnet II and IsoAir are lower power, they consume less energy and help reduce the impact upon natural resources.
To download the full Particle Counters and PoE paper, click here.