Fix Maxwell gain when 'lsb' is not in settings

[alejoe91]

In some older files, the lsb field might not be present in settings. In that case, the gain_uV can be computed as:

gain_uV = 3.3 / (1024 * gain) * 1e6

where gain is the amplifier gain, 3.3 is the ADC voltage range, and 1024 (10^10), is the number of bits of the ADC.

[pep8speaks]

Hello @alejoe91! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-07-09 15:51:19 UTC

[JuliaSprenger]

@samuelgarcia Any last comments from your side before we merge?