Ecomatik Granier - Model SF-G / SF-L -Sap Flow Sensors
Sap flow sensors are used to continuously measure water uptake in woody plants. It indicates if it is necessary to adapt the irrigation control. 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.
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
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
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…
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 | |