The selection of a level gauge should be based on specific operating conditions, medium characteristics, measurement requirements, and environmental conditions. It should not be based solely on price or accuracy.
Core Steps for Selection
Identify Medium Characteristics
Corrosiveness (e.g., acid, alkali) → Wetted materials must be corrosion-resistant (e.g., 316L stainless steel, Hastelloy, PTFE coating)
Viscosity / tendency to crystallize / presence of suspended solids → Avoid contact-type instruments such as float or magnetic flap gauges
Dielectric constant (εr) → Affects the reflection strength of radar/guide wave radar signals (caution if εr < 2)
Conductivity → Submersible and capacitive level gauges require the medium to be conductive
Analyze Process Conditions
Pressure: Atmospheric (open tank) vs. high pressure/vacuum (sealed tank)
Temperature: High (>150℃) or low (<-40℃) affects materials and electronic components
Agitation/Fluctuation: Violent liquid surface fluctuations affect ultrasonic and radar echoes; a stillpipe can be added
Foam/steam/dust: Interferes with ultrasonic; radar is more interference-resistant, but the antenna should be protected from clogging
Determine Functional Requirements
For local indication only: Magnetic flap, glass tube level gauge
Continuous analog output (e.g., 4–20mA): Radar, submersible, magnetostrictive, etc.
Switch output alarm: tuning fork, float switch
Requirement for explosion-proof / sanitary certification (e.g., food, pharmaceutical industry)
Installation and Environmental Constraints
Installation method: Top, side, bottom
Space limitation: Guide wave radar requires space for the probe
Protection level: IP68 suitable for long-term immersion (e.g., submersible)
Electromagnetic interference environment: Radar or magnetostrictive is preferred