How to determine what instrument is best for your application?
Well, It require very intense experience to do that. You know it when you have made mistakes and have a change to correct them. Only by facing the problems you can appreciate the impact of instrument selection, documentation, and installation on its serviceability.
Your instrument is like the window to look into the process and the selection and sizing of it requires a basic philosophy on how the equipment and processes is supposed to operate. Sometimes, the best instruments is the oldest and invented before you were born. Innovative and radical methods are good but it can make the plant engineers nervous.
But there are some simple guides for choosing your field instrument shows below:
For flowmeters, use orifice and DP transmitters as the first choice. For waste disposal type, acid, and bases services, you can use ultrasonic or magnetic flowmeters. For petroleum type liquid, use turbine in up to 12" pipe size and positive displacement type for the bigger pipe size.Vortex meters can be use for steam in up to 8" pipe size. For mass balance use coriolis type (but its only operated accurately in single phase homogeneous) .
For pressure transmitters, you can use anything. Just pick a range with your pressure in the middle.
Temperature transmitter, use 3-wire platinum RTDs. If you use thermocouples, use “J” thermocouples
Level transmitter, you can use a nuclear detector so you don’t have to ask the process engineer what the temperature, pressure, and specific gravity. for other type level transmitter you can read it in this link
To establish the integrity of your instruments, make sure there are three ways to measuring in critical operating parameter.