22.09.2024 /Testing

DC Resistance Unbalance Between Pairs

DC resistance unbalance between pairs is a measure how much the DC resistance of one wire pair differs from the resistance of another pair which is important to know when using Power over Ethernet. Read on to find out more about it.

DC resistance unbalance between pairs shows how much the resistance of one wire pair differs from the resistance of another pair. Other terms for DC resistance unbalance between pairs are Unbalance Pair-to-pair, Pair-to-pair Unbalance or P2PUbl.

DC resistance unbalance between pairs should be as small as possible.

As the wire pairs in a data cable have a different twist, they have a different total length and thus a different DC resistance. When devices are powered via the data cable the electrical current running down one pair differs from that running down another pair. The uneven load can lead to an oversaturation of the transmitter’s transformer and thus to lower power transmission. An oversaturation of the receiver’s transformer can cause signal distortion and thus to data transmission problems.

Trouble-shooting tips if DC resistance unbalance between pairs tests fail

Typical cause of the problem	This might help (without engagement)
Contacts in patch panel. outlet or plug are dirty	Clean contacts
Contacts in patch panel. outlet or plug are worn	Replace patch panel/outlet/plug
Contacts in patch panel. outlet or plug are corroded	Replace patch panel/outlet/plug
Wires in patch panel, outlet or plug are connected badly	Reconnect the wires
Wires in patch panel, outlet or plug have become loose	Reconnect the wires
Contacts of the test cord are dirty	Clean contacts
Contacts of the test cord are worn	Replace plug/test cord
Contacts of the test cord are coroded	Replace plug/test cord
Twist of wire pairs of the patch cord differs too much	Replace patch cord
Patch cord defective	Replace patch cord
Twist of wire pairs of the horizontal cable differs too much	Replace cable
Cable defective (material defect)	Replace cable