Repeatedly in the past we had found the ISS PD's DC level jump to a state past 10Volts to somewhere arount 12V. The last time this occured last night (alog 9637). Staring at the PSL ODC screen, it told us that two things were wrong: BIT7 "ISS actuation saturation" and BIT11 "NPRO Relaxation Oscillation" were red.
Last night we fixed the ISS actuation saturation by readjusting the set point, but the PDs remaind in the odd 12V state.
Staring at the ODC screen this morning, BIT11 "NPRO Relaxation Oscillation" remained red. Taking that suggestion by ODC seriously, I went out to toggle the NPRO noise eater. Sure enough - the the ISS PD's switched back to the normal "<10V" state, and BIT11 went green.
Conclusions:
- Our long-standing ISS PD mystery is caused by noise eater oscillations.
- The PSL ODC system correctly announced this problem.
FYI, The ODC overview screen is available from the SYS tab on the site overview, and has links to all subsystem screens. The subsystem screens have a description string for each bit. Currently fully operational -including meaningful thresholds -are PSL, IMC, ISI and HPI for all currently commissioned systems, as well as SUS for MC1, MC2 and MC3. (All SUS's have a working ODC system installed, but the good settings are still a moving target due to commissioning.
I put the ODC master screen on video5. Due to the many not yet commissioned systems, there is still a lot of red there. In the attached plot, there is even more red due to the ongoing IMC length measurement. (stay tuned)
Related previous alogs:
