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Rechner Sensors

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Rechner Sensors / applications / hotmeltglue / Hotmelt Glue

Level Detection of Hotmelt Glue

Download this application note as a PDF with connection diagrams: PDF


Level detection of hot melt glue has many technical hurdles that need to be overcome. Most sensors will not work in the extreme heat inside of the melting tank and will not be reliable due to the viscous nature of glue. This is especially true when the machine is turned off and the glue is allowed to harden. This also creates other stresses with expansion and compression of the glue changing states.

The solution is Rechner's KFS series of sensors. These durable sensors are designed to work in direct contact with the glue in extreme temperatures of up to 250 degrees Celcius for PTFE or PEEK housings (200 degrees Celcius for GFK housings) and can ignore massive amounts of glue build-up on the sensor to give you a reliable switching point the very first time you turn your machine on.

Hot melt glue level sensor


The sensor is mounted in the hot melt glue tank above the melting element. When the level of glue falls below the sensing point of the KFS sensor, a low level signal is sent to ask for more glue pellets.

The electronics for the sensor are kept in a remote location away from the hot melt tank. The adjustment for the KFS sensor is made on this KFA amplifier.

Adjustment of the amplifier takes place only after the KFS probe has been installed (mounted) and all electrical connections have been wired. Ensure that the Grounding Electrode (BE) is grounded to the tank in which the sensor is mounted.

For Hot melt tanks with grid systems, the sensor is mounted above the grid and detects when the level of glue is below a specified height. Refilling is usually accomplished manually or automatically with a short filling timer.

After installation, a 'full adjustment' of the amplifier is done in this order:

  1. Locate the sensitivity adjustment potentiometer on the amplifier. The actual adjustment potentiometer is recessed and may be located under a metal or plastic screw that is there to keep dust out.
  2. Fully immerse the sensor up to the switching point in hot melt glue after mounting the sensor in the tank.
  3. Reset the sensor's sensitivity by turning the potentiometer counter-clockwise 20 full turns, or until the sensor no longer sees the product (whichever comes first).
  4. Adjust the sensor to the product to be detected by turning the potentiometer clockwise until the sensor sees the product.
  5. Add 1/4 turn for safety by turning the potentiometer a further 90 degrees clockwise.

Parts Required:

  1. Sensor: KF0136
  2. Amplifier: AF0064
  3. Mounting Adapter: SA7004
Hot melt glue level sensor