How to read ethernet with oscilloscope?
How to read ethernet with oscilloscope?
Hello, I'm trying to connect my Tektromnix 2335 100Mhz oscilloscope to a Cat 5e Ethernet cable at 10BaseT. It seems to be on the orange wire pair, which should carry data, but the signal isn't showing up. I'm unsure if I'm using the device correctly. Any advice would be greatly appreciated. Thanks!
What connects your ground lead? Edit: You mentioned it links to the orange wire pair, so I’ll assume you have ground lead on either the orange or white/orange wires. Because Ethernet uses differential signaling, both wires are driven to specific voltages. Most instruments tie the ground lead straight to the mains earth. If this is true, your measurements might be affected—voltages shift, there could be noise, or readings become unreliable.
With your scope's math capabilities, you can apply the A-B function and link both probes to one wire from a pair. Connect the ground of both probes to the shielding on the Ethernet cable. In this setup, your scope should work by using the vertical mode "add" and selecting channel two, which acts like an A-B function. Ensure you use appropriate probes. If you only have standard X10 probes, operate them in X10 mode since most can only reach up to their maximum frequency there; in X1 mode they typically cover only 1...3MHz.