Evan G., Travis S., Heather F.

Since our previous measurement of the EY Pcal PD calibration had excess noise and glitches associated with other electronics, we made another round of measurements to verify the calibration of the Pcal PDs (see LHO aLOG 33392).

This time, we made sure that no other electronics were plugged into our supply, which resulted in better measurements and more accurate calibration, see attached figures. The peak-to-peak variation on the working standard (WS) measurements is ~4x smaller.

We find that that the calibration of the PDs is consistent with measurements made at the start of O2 to <=0.8% (see attached PDF). This appears consistent with historical variations made over the past 1.5 years. As additional measurements of the Pcal PDs are made, we will better constrain the variation in these measurements.

Finally, note that in early November 2016, we transitioned to a new working standard, so there is an offset in calibration values attributed to a new working standard PD responsivity.