There was some speculation that we might have a ground issue in the T240s, similar to what we had earlier with the GS13s.

To test this we lifted the shield to ground jumper in the corner #1 T240 electronics box on the ETMX-ISI. We then drove the system in the z direction (loops on, blends = start)

and looked at the individual T240 channels

  the first thing is that all of the Z channels look the same, so lifting the shield ground didn't effect anything here.

  the other thing is the horizontal sensors which have some coherence and a flat response which is kind of odd

  WE should remember to put the jumper back

  The second plot is the same set up except now I'm plotting the transfer functions to the modal T240 signals. We expect some cross coupling at the level of a 1-3% due to gain mismatch in the electronics, which

is kind of what you see in the vertical signals, the rX and rY are smaller then the Z by about the right factor and show the same slope. While the horizontal signals show something completely different, the 1/f^2 coupling that we have been working on