With the AEM analog wideband (part #30-5130) AEM's wideband/AFR gauges have come a long way. They released the original AEM UEGO with the red digital display about five years ago, and it was hunk of crap and completely useless for datalogging. Besides a high rate of manufacturing defects, even a working unit had had electrical noise problems for the analog signal and the voltage range was not truly linear. A couple years ago AEM revised the digital models, which now have a 0-5v AFR reading. The analog signal is still susceptible to electrical noise and won't fully agree with the display, even if you run a common ground to the Datalogit AN2 wire.
The AEM analog gauge appears to have finally fixed both the voltage range and the quality of the signal. It is designed to run with a signal wire and a floating ground wire. I just got to mess with one of these and it seems to work well. I am linking to two diagrams to help with setting it up.
The first diagram is the wiring. A white and brown wire comes off the main wideband harness. There is no blue serial wire like on the older models. The white wire should go to AN1 and the brown wire should go to AN2. The second shot shows how to set up the DL auxiliary input screen using the data provided by AEM. Click the "Poly" button and set the values as shown in the screenshot. Just FYI, AEM listed the transfer function as AFR = 2.375(V) + 7.3125
After that you should be good to go. It's not a digital display so therefore not as precise to read, but from what I can tell the gauge and the Datalogit seem to agree closely enough. The cool thing about an analog wideband is that you don't have to worry about a choppy display.
Hope this helps,