TJ, Eric, Oli

Yesterday TJ noticed that the 3-10 Hz and 10-30Hz seismic blrms for EX X-axis shifted up at some point in time and then later in the day, the values shifted back down(attachment1). The same thing happened today. It looks a lot like something turning on and off, so I tried looking at a bunch of FMC and PEM channels to try and narrow down what could be causing it. Looking through the PEM End Floor summary pages, the noise seems to be seen in the EBAY FLOOR accelerometers much more than in the VEA FLOOR accelerometers(attachment2,attachment3). It also looks like this on/off noise started showing up on February 20th.

I plotted the EX EBAY FLOOR accelerometer channel along with the 3-30Hz blrms channels and when the blrms channels are sitting higher, the EX floor accelerometer is less noisy, which seems backwards to me(attachment4). The fan accelerometer readings also match with this movement(attchment5). There also seems to be somewhat of a correlation between the acceleration and whether the EX_AH_DSCHRG temperature is higher or lower; when the acceleration is larger, the discharge air temperature is generally lower and vice versa, but that doesn't seem to be true 100% of the time.

I also don't know if this noise couples into DARM - I briefly checked the range blrms and didn't visually see any obvious drops or rises in the different bands with the changes in acceleration. I also didn't see any glitches on the glitchgram from when things go from on->off/higher->lower output/whatever is changing. I've told Eric about it.