- DLPCA-200 trans-impedance amplifier was calibrated.
  Keithley source meter 2450 was connected to the amp. Provide current and read the output voltage with the precision digital voltage meter (Agilent/Keysight).
  Gain: 999.7V/A@7mA, 999.6V/A@8mA

- From the power meter spec, Thorlabs S401C seemed the best (+/-3%). So the QEs of the 9 PDs were checked with this power meter again.

- All PDs exhibited the QE of 0.95~0.96. It's all relative as the power meter has a systematic error.
- Tried to clean B1-22 and B1-23 PDs. They didn't show significant improvement after the cleaning. To avoid the unnecessary risk of damaging the PDs, further cleaning was not performed. (Some photos were attached)

- What we can do is use this result as the relative measurements.
- For OMC#2, B1-22 is the DCPD(T) and B1-23 is the DCPD(R). C1-03 and C1-12 are the spares, according to this latest result.
- At LLO, we track down the source of the throughput reduction (-10%). The QEs of the PDs are going to be tested in the same setup at once to compare their PDs and our PDs.