As sales rate is low, ideally we'd buy an adaptor box with Ether to the PC and USB to our system. These are available for $30 from several companies.
Maybe, you are talking about USB-Ethernet dongles, like IOGEAR GUC210T.http://www.iogear.com/product/GUC210T/
Unfortunately, you can't use this kind of products. These products connect USB host (PC) to Ethernet.
To connect a USB device (your sensor) to ethernet, you need a Network USB hub / device server,
like Digi AnywereUSB, Lantoronix UBOX, etc.