Industrial Point Level Measurement

As opposed to continuous level measurement, point level measurement is used to measure liquid or bulk solids in a tank or vessel to a single, precise point. Most often used as a notification for high or low level, they are placed at the top or bottom of the vessel. When activated, the point level switch can activate an audible or visual alarm, start or stop a process, and/or notify a supervisory control system. There are several technologies that provide point level control, each with its own advantages and disadvantages. This post focuses the more advanced technology used for point level control, namely capacitance, vibration, microwave, and radiometric.

Capacitance Switch
Capacitance Switch

Capacitance Switches

  • Measure the capacitance of the process medium’s ability to hold an electrical charge.
  • Can be used with both conductive or non-conductive liquids and solids
  • Looks for step changes in standing capacitance.
  • When media reaches the area between the two plates, the capacitance changes, and the switch output changes state.
  • Must be installed and set up in process to know the different capacitance values for a vessel that’s full and a vessel that’s empty.

Vibration Switches

Vibration Switch
Vibration Switch
  • Constantly vibrate at a specific frequency.
  • The frequency or amplitude is monitored to determine when a liquid or a bulk solid has reached the switch point. 
  • Once the medium contacts the sensing probe, the frequency or the amplitude changes and this change activates the output.
  • Easy installation.
  • Are "plug and play".
  • No media calibration requirement.
  • Little or no maintenance costs.

Microwave Switches

Microwave Switch
Microwave Switch Emitter
  • Non-contact.
  • Utilizes an emitter and receiver.
  • Use a microwave beam to determine point level. Once the bean is broken, a switch changes status.
  • Not only used for high or low level, but also for determining id material is filling a vessel or falling to a conveyor.

Radiometric Switches

  • Non-contact
  • Utilizes an emitter and receiver.
  • A detector measures the amount of gamma radiation from an emitter and determines point level when a threshold is met.
  • Can be installed externally, with no vessel penetration.
  • Good for volatile and hostile processes.
  • Radiometric Switch
    Radiometric Switch
  • Can measure changes in gamma radiation and be used to detect building vapors.

For more information or any process level requirement, contact Classic Controls by visiting or by calling 863-644-3642.