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
