Cable Diameter Standards
|Area (metric)||Diameter||American Wire Gauge||Resistance||Ampacity||Typical Use|
|0.08 mm²||0.32 mm||AWG28||200 mΩ/m||0.8 A||Thin wires inside a data cable|
|0.10 mm²||0.36 mm||AWG27||160 mΩ/m||1 A||Thin hobby wire (home electronics for up to 30cm)|
|0.14 mm²||0.40 mm||AWG26||125 mΩ/m||1.3 A||Cat5 UTP, Flexible hobby wire|
|0.25 mm²||0.50 mm||AWG23 / AWG24||65 mΩ/m||3 A||Cat5e UTP, breadboard wires, Thicker hobby wire|
|0.50 mm²||0.80 mm||AWG20 / AWG21||32 mΩ/m||5 A||High quality Cat6 STP, Low voltage power cable (e.g. for phone or doorbell or powering electronics)|
|0.75 mm²||1.0 mm||AWG18 / AWG19||20 mΩ/m||10 A||Power cable between outlet and device|
|1.5 mm²||1.3 mm||AWG16||13 mΩ/m||12 A||Thin power wire in walls (black wire for switches)|
|2.5 mm²||1.6 mm||AWG14||8 mΩ/m||15 A||Normal power wire in walls (power, zero and earth wire)|
|6.0 mm²||2.5 mm||AWG10||3 mΩ/m||30 A||Thick wire in electric panel (groepenkast)|
The metric area is the advertised area, equivalent of mm² copper. The actual diameter, when translated from AWG specification may differ.
The ampacity is the sustained current that can be transported through the wire without exceeding its temperature rating. In this case, the Ampacity at 60°C is given. For higher acceptable temperatures (75°C or 90°C), multiply by 1.5. Peak currents may be 10 times larger if they are short enough (< 10 seconds).
Note that the thickness of the cable is determined by the current (amperage), not by the voltage or power. So a lower-voltage installation requires thicker cables than a higher-voltage installation with the same power consumption. The current (in Ampere) can be calculated by dividing the Power (in Watts) by the Voltage of the appliance.
The thickness of the insulation depends on the voltage, and is not mentioned in this table.
- solid or flexible. A solid core is often used for fixed wiring, and for breadboard wires. Flexible wire contain multiple small strands and is used for flexible cables.
- copper of CCA (copper cladded aluminium). Copper is considered slightly better. CCA is cheaper and is consider good enough.
|Ethernet Category||Max. Frequency||Max. Transmission Speed (@ Max. distance)||Cable type||Number of wires||Remark|
|Cat3||16 MHz||10 Mbps @ 100m||U/UTP||2||Obsolete. Used for voice.|
|Cat5||100 MHz||100 Mbps @ 100m||U/UTP||8 (4 used)||Obsolete. Replaced by Cat 5e.|
|Cat5e||100 MHz||1 Gbps @ 100m||10 Gbps @ 45m||U/UTP||8|
|Cat6||250 MHz||1 Gbps @ 100m||10 Gbps @ 55m||F/UTP||8||Has separator between the 4 wire pairs|
|Cat6a||500 MHz||10 Gbps @ 100m||F/UTP||8|
|Cat7||500 MHz||10 Gbps @ 100m||S/FTP||8||Uses GG45 or TERA connectors. Obsolete by Cat 6a|
|Cat7a||600 MHz||10 Gbps @ 100m||S/FTP||8||Obsolete by Cat 8|
|Cat8.1||2000 MHz||40 Gbps @ 30m||U/FTP||8||Uses regular 8P8C ("RJ45") connectors.|
|Cat8.2||2000 MHz||40 Gbps @ 30m||S/FTP||8||Uses GG45 or TERA connectors.|
|Systematic Name||Old name||Cable protection||Wire-pair protection|
|SF/UTP||S-FTP||Braiding and foil||None|
|SF/FTP||Braiding and foil||Foil|
|U = unshielded|
|F = foil shielding|
|S = braided shielding (outer layer only)|
|TP = twisted pair|
When shielding is applied to a collection of pairs, it is usually referred to as screening, hence STP (Shielded Twisted Pair) is sometimes abbreviated to ScTP (Screened Twisted Pair).
Power over Ethernet
|Standard||Non-standard||802.3af (802.3at Type 1)||802.3at Type 2||802.3bt Type 3||802.3bt Type 4|
|Power available at device||9.0 W||12.95 W||25.50 W||51 W||71 W|
|Maximum power delivered by power supply||12.0 W||15.40 W||30.0 W||60 W||100 W|
|Voltage range (at power supply)||24.0 V||44.0–57.0 V||50.0–57.0 V||50.0–57.0 V||52.0–57.0 V|
|Voltage range (at device)||17.5-24.0V||37.0–57.0 V||42.5–57.0 V||42.5–57.0 V||41.1–57.0 V|
|Maximum current Imax||500 mA||350 mA||600 mA||600 mA per pair||960 mA per pair|
|Maximum cable resistance per pairset||8 Ω (2× 4 Ω)||20 Ω (2× 10 Ω)||12.5 Ω (2× 6.25 Ω)||12.5 Ω (2× 6.25 Ω)||12.5 Ω (2× 6.25 Ω)|
|Power management||None (always on)||Three power class levels negotiated by signature||Four power class levels negotiated by signature or 0.1 W steps negotiated by LLDP||Three power class levels negotiated by signature or 0.1 W steps negotiated by LLDP||0.1 W steps negotiated by LLDP|
|Derating of maximum cable ambient operating temperature||None||None||5°C with one mode (two pairs) active||10°C with more than half of bundled cables pairs at Imax||10°C with temperature planning required|
|Supported cabling||Category 5||Category 3 and Category 5||Category 5||Category 5||Category 5|
Note that there are many "Passive PoE" applications. The given 24V is common for Ubiquiti devices that support Passive PoE. Other applications carry up to 1.0 A at 24V, 48V or even 56V.
The tables allow for calculations of power budget of PoE devices. Imagine an access point powered by 24V passive PoE, using a good Cat 5e cable, which has a 42 mΩ/m resistance. A 15 meter cable has 30 m wire (going forth and back) and has thus 12.6 Ω resistance in total. With a maximum current of 0.5 A (determined from either the PoE table or the Ampacity of AWG22 wire), this translated to a drop in voltage of 0.63 Volt. Thus only 23.37 Volt of the original 24 Volt is left for the access point, translating to maximum of 11.7 Watt (with the 0.5 A).
In general, you will find that there is no problem with short cable of 10 or 20 meter, but you may hit power limitations when using a cable of the maximum length of 100 meter.
For UTP cabling:
- Welke kabel moet ik kiezen? by Daniel Spijker (Dutch)
- Demystifying Ethernet Types— Difference between Cat5e, Cat 6, and Cat7 by Rita Mailheau