sap flow meter

Sap Flow Meter

Sap Flow Meter

sap flow meter

The measurement of sap flow in trees enables the calculation of daily and seasonal water use. Using this, irrigation requirements (urban parks, orchards & forests), tree health, the impact of climate change and calculation of carbon storage can all be derived through sap flow measurement. The SFM1x Sap Flow Meter quantifies tree water use in litres by measurement of sap flow.

The SFM1x is a self-contained instrument comprising sensor, signal processing, data storage and data transmission. The SFM1x is available with Internet of Things (IoT) connection, including LoRaWAN, CAT-M1 and NBIoT. The standard Bluetooth connectivity enables quick wireless device configuration, and data transfer in the field once installed.

IoT connectivity enables the SFM1x to transmit data directly to the cloud. This allows for further processing and analysis, visualisation and presentation, or integration into existing dashboards through an Application Programming Interface (API).

Using the established Heat Ratio Method, the SFM1x can measure high, low, and reverse flow rates in small woody stems and roots, as well as large trees. The SFM1x remains key for both researchers and industry to understand tree water use. Typically raw temperatures are stored and converted to sap velocity.

The SFM1x can optionally measure sap flow using the Compensated Heat Pulse Method (CHPM) and TMax methods. These methods can be used because the SFM1x stores the raw temperature data (recorded every 1 second) as JSON or CSV files. The JSON or CSV file result in ease of data access for the additional processing required outside of the instrument. The use of Senaps can allow this processing to be undertaken in the cloud in real time (this will incur additional charges).

The Sap Flow Meter (HRM30 and SFM1) has over 400 listings in Google Scholar, highlighting the wide acceptance by the research community. ICT International has an active library of over 75 leading publications that can be accessed here.

Communication Technology Options

The SFM1x is an IoT enabled Sap Flow Meter is available in the following versions:

  • SFM1C uses CATM1
  • SFM1L uses LoRaWAN
  • SFM1B uses a dedicated, long range Bluetooth with external antenna

The use of these communication technologies enables the SFM1x to be deployed wherever there is cellular network coverage, or if there is no cellular coverage, a network using LoRaWAN and subsequent internet connection via 4G or satellite backhaul.

All SFM1x versions contain a Bluetooth module with an internal antenna for wireless data access and configuration of the unit. The SFM1B has a dedicated external Bluetooth antenna allowing long range connection.


The principles behind the SFM1x – the Heat Ratio Method – have been used to measure plant and tree water use in many applications. Example applications of the SFM1 and HRM30 can be found in:

4 thoughts on “Sap Flow Meter”

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