Sheila, TVo
In attempts to switch DARM control from ETMY ESD to other methods (see aLOG-37984), we wanted to see if the ITM ESDs had enough range to be able to take on the DARM control signal during locking as well as estimate the ratio of low noise response.
Configuration:
| ETMX | ITMX | |
| Digital Gains | -39.2 | -7.0 |
| L3 Filters | Same | Same |
| Analog Driver Gains | 2 | 2 |
We can compare the respective responses by dividing out the digital and driver gains and then taking the ratio between ITMX and ETMX TFs.
The first picture is the individual TFs and the second picture is the ratio of the magnitudes as a function of frequency.
Sheila trended a lock acquisition and found a time where the ETMX ESD was driving the hardest so we made an RMS measurement to get a sense of what is needed to lock. Then we can estimate what is needed from the ITMX ESD and see if it is close to saturating the 18-bit DAC, also attached is the calculation.
Conclusions:
1) The ratio of ETMX to ITMX ESD drive is about 3.
2) The ITMX ESD range has enough range to lock with DARM, we'd only use up about 12% of DAC range.
