Instrumentation Question:
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What is Instrumentation Measurement?


Instrumentation can be used to measure certain field parameters (physical values):

These measured values include:

* pressure, either differential or static
* flow
* temperature - Temperature_measurement
* level - Level Measurement
* density
* viscosity
* radiation
* current
* voltage
* inductance
* capacitance
* frequency
* resistivity
* conductivity
* chemical composition
* chemical properties
* various physical properties

It is the process of comparing know and unknow value under measurment and get a resultas numerical value

1) In this range instrument shows linearity.
2) Almost all instruments uses 24V DC power supply hence at this level no major spark is possible.
3) 4-20 MA means 16 Ma so it is easy to use 4 bit system to form 16 combinations to measure value of current.
4) if instrument fails its output is lower than 4 MA so we can guess that something wrong is happening with an instrument. ( live zero an dead zero)
5) if someone ask why not 0-20? the answer is external noise can create current up to 3 MA,so to distinguish between field signal and noise signal we use 4-20 Ma range.


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