Instrument Ranges Used in Process Control System Design ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

Instrument Ranges Used in Process Control System Design

In process control design process variables such as temperature, pressure, flow, level, valve signals, analyzers etc are ranged in such a manner to be proportional to the primary signal as much as possible for control purposes. The table below shows the typical instrument scales employed in process control system design:

Instrument Variable

Scale

Temperature

Direct Reading

Pressure

Direct Reading

Flow (differential)

0 – 100 linear

Flow (Linearized)

0 – 100 linear

Level

0 – 100 linear

Analyzer

Direct Reading

Signal to Valves

0 – 100%

As far as possible, the instrument ranges will be selected such that the normal value will be between 50 and 75% of the adjusted range taking into account the specified minimum and maximum values and trip settings will lie between 10% and 90% of the adjusted range.

Typical accuracy of the pressure and differential pressure Smart transmitters will be +/- 0.25% of the calibrated span.

Typical accuracy of temperature Smart transmitters will be +/- 0.3% of the calibrated span.

Typical accuracy of the other transmitters will be as far as possible better than +/- 0.5%.



You May Also Like: