Additons regarding the amplitude of excitation

Here are a few ideas we have discussed that I'll list here as potential features of the code

- A user set hard limit on the amplitude and/or the rms of the injected excitation of the system. This would help ensure that the specified power does not accidentally drive the system too heavily at a particular frequency. This would be a preventative measure rather than the current features that exist for this which seem to only check after the signal has been injected.
- Sending in a small test excitation (0.1% or 1%) of the planned excitation as a safety check.
- A way to specify the power of the excitation relative to the background measurement taken. This would allow the magnitude of the injected signal to be specified in terms of a metric related to SNR rather than total power, which may be an easier way to quickly determine how much power this injected signal will have.

No files, tests, or entry points are named. First locate the code that injects excitation and records background measurements, then clarify which of the three proposals is in scope and define acceptance criteria for its amplitude, RMS, test-excitation, or relative-power behavior.

Written by the indexing model from the issue text.