1. DAQ Errors John Zweizig LIGO/Caltech LSC Analysis Meeting Tufts June 6, 2004

2. Error Description ● Invalid VME-bus protocol in timer module – Low byte modified when IRQ5 asserted during block transfers. – Errors occur every 62.5ms for a ~0-25 s. ● Control crate – Weakly synchronized with data – all channels can be affected

3. Appearance ● Errors separated by multiples of 16 bytes ● Errors seen in clusters of 1 to ~5. ● Bits usually jammed 'on' – Int_16: signed value increases by ~2 × 10 -3 – Float: Absolute value increases by ~10 -5 Example errors in int_16 channel

4. Examples Seen ● Steady int signals, e.g. SUS Sensors (IFO locked) ● Signals with known LSB – Data Valid word – Floats containing small ints. ● Known signals – Calibration lines ● Collateral damage: Data zeroed if DataValid !=0. Errors in calibration lines black: Lines notched out × 10 3

5. Position in LHO DAQ Stream H1-AS_QH2-AS_Q Note: Black arrow: my estimate, magenta arrow: Ben's calculation AS_Q length = 4100 bytes (small) (Plot by B. Johnson)

6. Position in LLO DAQ Stream L1-AS_Q Note: Black arrow: my estimate, magenta arrow: Ben's calculation AS_Q length = 4100 bytes (small)

7. Simulation ● Stochastic DaqErr “filter” in DMTGen – Fixed- or random-width error clusters – Random times ● rate parameter ● anchored to slice boundary – LSB forced to 0xFF – Applied to any channel

8. Effect on Spectra Inject errors in AS_Q: =4, =1Hz Conclusions: Extra power ~10 -5 × noise, distributed through spectrum. Not visible! red: AsQ data with generated errors (AsQ ERR ) black: Difference in PSD w/wo errors ( psd{AsQ ERR } - psd{AsQ}) x10 3

9. Induced Glitches? ● Prepared prepared H1, H2 AS_Q samples without and with errors (2 Hz errors, 4 sample clusters) ● Ran through PSLmon glitch tool with 6  threshold, various filters. ● No excess triggers found in error-injected data.