I investigated why the H1 frame is about 20% larger than the L1 frame. Using the set of INI files in the running configuration for both DAQs, I ran them through Jim's inicheck program. I removed the systems which are H1 only (PEM at midstations and SUS-QUADTST in LVEA). To remove the frame size compression ration, I am comparing raw data rates not size of frames on disk.

So H1 has 0.4% more slow and 0.25% LESS fast channels but 4% MORE data in the science frame.

I took the H1 and L1 science frame channels lists, removed all 16Hz channels, converted L1 to H1, sorted them alphabetically and compared for fast channels missing from L1 frames or having higher datarates in the H1 frame. The PEM system stood out with the biggest differences.

This summer Robert asked for many 2kHz channels to be increased to 8kHz and some added to the science frame. Looking at the PEM channels for EX, EY and CS, H1 has 1.8MB/s more data than L1. In the above table, 28.9 + 1.8 = 30.7, close to the H1 number of 30.2 (difference is most probably due to L1-only channels like CS-CAL).

As an aside, I was surprised that the science uncompressed rate was so high compared with the frame size. For H1 this ratio is 30.2 vs 12.5 which is a compression factor of 2.4. Greg confirmed that he is seeing compression rates around 2.7 using frcheck.

I also found that the compression rate and therefore the frame size depends on the state of the interferometer. As one would suspect, if ADC data has higher AC components, the compression factor will decrease. For example, I trended the frame size against the Guardian state of the DRMI locking system, there is a clear correlation (see attached plot). The size of the frame has varied by 6%.