The Process Chiller Pro
The Process Chiller Pro
PLC Control Series– Understanding PLC INPUTS – Process Chiller Pro Podcast
There is an old term I want to bring back to life because I think it fits well within the context of this episode in my series on PLCs.
This term is “Garbage is equal to Garbage Out.”
This term zero’s in on when you feed a computer bad or unexpected data, the output or result will also be bad or unexpected.
Well, PLCs used in HVACR and Process Chiller equipment is no different.
We will first explore what digital and analog inputs are, and I will refer to these as classes of inputs.
After that, we will look at three of the most common input types within the two classes.
The three specific input types we will look at are:
- Dry Contacts are commonly used for event confirmation.
- Thermistors that measure temperature.
- Transducers are commonly used in refrigeration machines to measure refrigerant pressure.
Once you understand PLC input classes and the three most commonly used types, we will look at how to diagnose each of the input types using an ohmmeter and the hopscotch electrical diagnostic method.