Different level measuring systems : A Comparison

ADVANTAGES/DISADVANTAGES OF LEVEL MEASURING SYSTEMS:

Here below is a table showing the comparison of different level measuring systems I have posted before. The table gives the advantages and disadvantages of different methods along with the principle they use.

PRINCIPLE	SYSTEM	CHARACTERISTICS
		ADVANTAGE	DISADVANTAGE
SIGHT	DIPSTICK	Simple, cheap, instant	Need to remove to read
	SIGHT GLASS	Cheap, fairly foolproof, pressure up to 700 Mpa and 300oC	Need to careful handling, brittle.
	TAPE/FLOAT	Cheap, can be used with corrosive liquids, but opening for tape.	Low pressure/ atmospheric only. Can Stick.
	POTENTIOMETER FLOAT	Voltage output as above	Stiction
	MAGNETIC	As above	Stiction
DISPLACERS	SPRING BALANCE	Can be used for interfaces, limited range.	Expensive
	TORQUE  TUBE	Most displacer transmitters use this, accurate but limited range.	Limited range.
PRESSURE	PRESSURE GAUGE	Cheap, open and closed tank.	Not available readily in low range in H2O.
	BUBBLER METHOD	Can be used for slurries, or corrosive mixtures.	Requires air supply.
WEIGHT	LOAD CELLS	Accurate non-contact method.	Need frequent recalibration.
ELECTRICAL	CONDUCTIVITY	Rugged, requires little maintenance.	Limited to conductive liquids.
	RESISTANCE	Rugged, requires little maintenance.	First few inches not accurate.
	CAPACITIVE	Rugged and accurate.	Tank must be metal if only probe is used.
ULTRASONIC	ECHO TYPE	Non-contact	High pressurize wont work, expensive.
RADIATION	ABSORPTION	Non-intrusive.	Expensive, not accurate, hazardous source.
THERMAL	THERMISTOR	New method, cost reasonable.	On/Off only

Article Source: Level Measurement by N. Asyiddin