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Sap flow sensors

🌿 Sap Flow Sensors – Accurate Monitoring of Liquid Flow in Trees

The primary function of all sap flow sensors is to measure temperature changes along the tree after applying heat to a specific point. This process is based on the principle that the applied heat is transferred by the sap moving through the tree, and the rate of heat transfer correlates with the sap flow rate.

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Available Models:

SF-G & SF-L Sap Flow Sensors (Granier’s Principle)

  • SF-G Model: This model is based on the classic sensor developed by André Granier in 1985, featuring two insertion needles.

  • SF-L Model: An enhanced version of the Granier sensor with four needles. Patented improvements correct natural vertical temperature gradients in the tree sap. Without these corrections, natural temperature variations can cause measurement errors of up to 50%. The SF-L sensor provides more accurate data by measuring and adjusting for these gradients.

Advantages of SF-L Model:

  • Higher accuracy in sap flow measurement.
  • Correct determination of zero sap flow using additional dendrometer measurements.
  • Enables measurement of nighttime sap flow.

Limitations of SF-G Model:

  • Measurement values can overlap with natural vertical temperature fluctuations, leading to errors of over 50%.
  • Nighttime sap flow cannot be measured as nighttime values must be set to zero.

Limitations of SF-L Model:

  • Not suitable for trees with diameters smaller than 8 cm.
  • Requires 3 data recording channels per sensor.

SF-HP-N3D2 & SF-HP-N3D3 – Heat Pulse Sap Flow Sensors

These sap flow sensors work on the principle of a heat pulse instead of constant heating. A brief heat pulse is applied, and the spatial spread of the heat is measured to determine sap flow speed and direction. Multiple measuring points along the needles allow for a detailed radial profile of sap flow.

Advantages of HP Sensors:

  • Significantly reduced power consumption compared to constant-heating sensors (e.g., TDP sensors).
  • Equipped with multiple measurement points to capture the radial depth profile of sap flow.
  • Capable of detecting reverse flow and utilizing the “Dual Method Approach” for accurate measurements across all flow rates.

HP Sensor Customization:

  • Needle lengths and measurement point positions can be adjusted upon request for plants with smaller diameters.

Limitations:

  • Measurements cannot be conducted continuously; the maximum time resolution is 10 to 15 minutes.

🌿 Benefits of HP Sap Flow Sensors:

  • Lower energy consumption.
  • Stronger analog output signals (in the volt range).
  • Durable and resilient sensors.

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