|The process defined below will demonstrate how to measure voltage applied to a device via Power over Ethernet (PoE) using the DTX-NSM Network Connectivity test. |
What is PoE?
Power over Ethernet or PoE is the ability to provide required power to a Powered Device (PD). This power is applied by detecting the link for a device requiring power, then supplying the required power.
"Excessive Voltage" reported
- A POE source is not supposed to put out power until a device negotiates for it.
- The negotiation voltages are in the sub 10 volt range.
- If the NSM sees over 15 volts, it will report excessive voltage.
- Once negotiated, the output voltage should be in the 44 to 57 volt range.
- It will also report excessive voltage over the "Safe" level of 58 volts.
To measure the power applied to a device with the DTX-NSM:
b. PoE is red if the device advertised PoE but did not supply power during the test.
c. If PoE is not displayed the device did not advertise PoE capability.
d. Fiber shows for a fiber link.
Note: The DTX-NSM will detect PoE voltage, but will not run on links with ground loops, analog telephone Voltages, ISDN voltages, or other voltages. The DTX will warn you if it detects these conditions.