Please click for enlarged view; The hose pump generates a pressure in the bubbling through tube (pulse). At the end of the tube air escapes, when the hydrostatic pressure is reached (density x filling height). The existing pressure is transferred continuously to the system. After each break the process repeats again. If the level of the liquid changes during the break, the output signal follows because the built-up pressure in the tube changes at the same time. Note: Maximum distance of point of bubbling through 50 m

For applications in all ranges where conventional level measuring is not possible or too expensive, Müller Industrie-Elektronik offers the ADLM-P using the procedure of the bubbling-through method for pneumatic liquid level measurement. Ranges of application are clarification plants, pump houses, in well building and construction of special vehicles (tanks for water and fuel) and even so in chemical and in foodstuff industry.

Procedural, for the ADLM-P air is pressed through a tube dipped down into the medium. The lower end of the immersion tube has a fixed distance from the bottom of measuring site (container, drain). The pressure of the injected air in the tube is increased until the hydrostatic pressure of the liquid is reached. This condition becomes manifest in the form of tiny air bubbles escaping from the tube end and are noticeable at the surface.

Thus, this hydrostatic pressure is a measure of the pressure at the bottom of the tube, which consists of the medium level. Since the pipe has a fixed mounting position, this pressure changes whenever the level of the medium changes. The variable pressure signal will be evaluated and read out as a standard signal. Even a volume calculation over 20 interpolation points for linearization (calculated by density-pressure-determination) as well as system integrations to Modbus, CANopen and Profibus are easily feasible with the ADLM-P.

Advantages of bubbling-through pressure transducer

• Level measuring possible in all liquids
• No contact between sensor and medium, aggressive media are smoothly measurable (disadvantage with diving probes)
• No extensive mechanical construction required (e.g. pressure sensors need an access below the tank)
• Cost-effective solution (in contrast to radar technique)
• Foaming has no influence (problem with ultrasonics)
• Easy mounting
• Reliable function

Technical Characteristics

• Input: positive relative pressure (hydrostatic pressure)
• Analog output: 4...20 mA / 0...10 V (standard version)
• Voltage supply: 24 VDC +/-20%
• Combined error: ±1% FS
• Limit contacts: 2 relays (optionally)
• Indication: LCD-display
• Electrical connection: plug-in terminal strip
• Pressure connection: for 6 mm plastic pipe
• Degree of protection: IP 65
• Interface (option): RS485 Modbus/CAN-Bus/Profibus
• Data output: interfaceRS232
• Volume calculation: 20 interpolation points for linearization