SF-G / SF-L Granier Sap Flow Sensors

    Sap flow sensors are used to continuously measure water uptake in woody plants. The SF-G model corresponds to the classic, two-needle model developed in 1985 by André Granier.

    Our four-needle SF-L sensor is an updated Granier sensor. The patented improvements correct the naturally occurring and time-varying vertical temperature gradients in the sapwood. Without correction (i.e. the original Granier sensor, SF-G) and despite isolation, these natural temperature gradients can lead to a temporary over- or underestimation of the measured sap flow values of up to 50% in extreme cases (cf. Do, F., & Rocheteau, A., 2002). Additional temperature measurements with the SF-L sensor enable a correction of the measured sap flow values, which prevents errors caused by the natural vertical stem temperature gradients. This results in a significantly higher accuracy and a stabler zero-point (ΔTmax) of the xylem (sap) flow.

    A very helpful option to exactly determine this zero-point would be to use a dendrometer in order to continuously measure the water saturation level of the tree body. This additional measurement allows for a precise determination of zero sap flow conditions: sap flow = 0 if the relative humidity in the crown at 100% and the tree body is 100% saturated with water (no change in diameter according to the dendrometer data). The improved SF-L sensor combined with dendrometer-aided precise determination of zero flow conditions, makes a running nocturnal zeroing of the sap flow (according to Granier) unnecessary. This process enables the recording of a nocturnal xylem flow.

    Advantages

    Specific to the SF-G model

    • Suitable for tree diameters > 1 cm

    Specific to the SF-L model

    • Greater measurement accuracy
    • Correct determination of the xylem flow zero point when supplemented with dendrometer measurements
    • Allows measurement of nocturnal xylem flow
    • Additional information about tree growth provided by installing supplementary dendrometers

    Limits

    Specific to the SF-G model

    • The measured values are superimposed by naturally occurring vertical temperature fluctuations in the trunk (up to +/- 2.5 ° C). This leads to measurement errors greater than 50% and may impact the reliability of measurement results.
    • Nocturnal sap flow cannot be measured. Because of the temperature overlaps, nocturnal measurement values have to be set to zero.

    Specific to the SF-L model

    • Not suitable for trees with a diameter < 8 cm
    • 3 logger channels are required per sensor

    Models

    Model name

    Suitable for diameters

    Sensor needle // heater element length in mm


    SF-G
    > 1 cm18 // 10

    > 2 cm
    33 // 20
    43 // 20
    63 // 20
    SF-L> 8 cm18 // 10
    33 // 20
    43 // 20
    63 // 20

    Technical Data

    Sensor model name

    Sap Flow Sensor

    Type SF-G

    Type SF-G

    Scope of application

    For continuous measurement of the sap flow in wood plants

    Suitable for diameter

    > 1 cm

    > 8 cm

    Number of sensor needles

    2

    4

    Sensor dimensions

    Needle diameter: 1.5 mm;

    Needle length//length heated in mm, available versions:

    18//10; 33//20; 43//20; 63//20

    Output signal

    Analog, DC voltage -100µV to +800 µV

    Required logger channels

    1x differential, resolution better than 10 µV

    3x differential, resolution better than 10 µV

    Power supply

    Sap flow sensors must be supplied via a constant current source (CCS). A CCS supplies up to 3 SF-G and / or SF-L sensors and continuously needs 85 mA x 12 V. This corresponds to 2.1 amps x hour / day.

    Sensor cable length

    5 m, extendable to max. 20 m

    Manual

    Technical data sheets

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    Accessories & Compatible Products

    Compatible sensors and peripherals:

    Our open and modular system is highly flexible and easy to expand in stages. In this case, virtually all sensors or other peripheral devices (such as a webcam) can be integrated.

    Ecomatik sensors include:

    • Dendrometers
    • Sap flow sensors
    • Temperature sensors
    • Leaf sensors
    • Humidity and air temperature sensor
    • Soil moisture sensors
    • And many more…

    Contact

    You need a quotation, have questions about a product, or need extensive technical advice in the context of your project planning. Starting with an initial determination of your needs, through the detailed planning of the required measurement equipment and data transmission technology, up to professional implementation on site, we are at your disposal at any time with advice and action.

    General information on order processing

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    Assessment of your needs

    With your consideration and input, we determine which of our products best meet your needs. We are also happy to design fully-integrated measuring stations (plant, climate, soil sensors), including an independent power supply and mobile data transmission, depending on your requirements.

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    Your contact details and Assessment of your needs

    Like so many things, everything started with an idea ...

    In the case of the plant scientist and founder of ECOMATIK, Dr. Liu, it was the idea that modern measurement technology should enable crucial plant physiological parameters to be measured directly, precisely and with high temporal resolution on the plant itself. It was obvious to him that there is an information potential of immense value in the detailed understanding of immediate reactions of plants to their environment...