TM1K2 PLC limits and IM4K2 ppm 24-bit readout fix

[jyotiphy]

Description

• Disable PLC limits for TM1K2 for now until we have all targets setup with their setpoints/delta
• Fix fTermMin for IM4K2 ppm 24-bit readout

Motivation and Context

Attempt to fix scaling for 24-bit ppm readout

How Has This Been Tested?

Haven't yet tested

Screenshots (if appropriate):

Pre-merge checklist

• Code works interactively
• Code contains descriptive comments
• Test suite passes locally
• Libraries are set to fixed versions and not Always Newest
• [ x] Code committed with pre-commit (alternatively pre-commit run --all-files)

[ZLLentz]

Reference link to the underlying bug that requires us to handle the analog input this way: pcdshub/lcls-twincat-general#54

[jyotiphy]

@ZLLentz Changing TermMin value to 0 gives, raw voltage of about -68mV. Phil said that he's expecting ~10mV. 🤔

[ZLLentz]

Well, that's much better than the -10V we saw before!
Maybe it's worth checking the pins with a multimeter to confirm the behavior?

We need to separate any potential grounding/wiring issues from code issues and address them separately.