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Enabling better global research outcomes in soil, plant & environmental monitoring.

SFM1 Sap Flow Meter

The SFM1 Sap Flow Meter is a self contained, stand-alone instrument for the measurement of sap flow or transpiration in plants. The SFM1 is a complete package containing sap flow sensors, data logger, interface software and internal battery which can be charged with an external solar panel. The SFM1 Sap Flow Meter is a new model which replaces the HRM30 sap flow measurement sensor.

Utilising the Heat Ratio Method (HRM) principle the SFM1 Sap Flow Meter is able to measure high, low and reverse flow rates in both small woody stems & roots as well as large trees. Like the Heat Field Deformation (HFD) principle, the HRM Sap Flow Meter is the only instrument that can measure zero flow and reverse sap flow rates. The SFM1 Sap Flow Meter is the most powerful and flexible instrument for the direct measurement of plant water use.


  • Low & Zero Sap Flow Rates
  • Reverse Sap Flow Rates
  • Night Time Water Loss
  • Stem Sizes>10mm
  • Sap Flow in Roots
  • Arid Ecosystems & Drought
  • Radial Sap Velocity Profiles
  • Sap Flow of Grapevines




A Selection of SFM1 Sap Flow Meter Youtube Videos:


Unboxing Video – Indonesian

SFM1 Sap Flow Meter Unboxing Video


Installation Video – Indonesian

The Heat Ratio Method

Developed by the University of Western Australia and partner organisations, ICRAF and CSIRO, the HRM principle has been validated against gravimetric measurements of transpiration and used in published sap flow research since 1998. Burgess, S.S.O., et.al. 2001 An improved heat pulse method to measure low and reverse rates of sap flow in woody plants Tree Physiology 21, 589-598. Heat Ratio Method (HRM) is an improvement of the Compensation Heat Pulse Method (CHPM). Being a modified heat pulse technique power consumption is very low using approx 70 mAmp per day at a 10 minute temporal sampling interval under average transpiration rates. The HRM needles have two radial measurement points for the characterisation of radial sap flow gradients making measurements more accurate.

 Installed SFM1
Through microprocessor control, the inner measurement point can be activated or deactivated dependent on the specific wood anatomy of the species being measured. This provides a great flexibility in stem diameter range from >10 mm diameter woody stems or roots to the world’s largest trees, thus enabling water flows to be monitored in stems and roots of a wide range of different species, sizes and environmental conditions including drought or water stress.

Instrument design

The SFM1 probes consist of three 35mm long needles integrally connected to microprocessors. The top and bottom probes contain two sets of high precision thermistors located at 7.5mm and 22.5mm from the tip of each probe. The third and centrally located needle is a line heater that runs the full length of the needle to deliver a uniform and exact pulse of heat through the sapwood.

Instrument Configuration & operation

All aspects of the instruments operation and calculations are controlled by the microprocessors which automatically convert the analogue signals to a calibrated output. Programming variables such as heat pulse interval, energy input, probe spacings, and measurement frequency are all held resident in non-volatile memory. The SFM1 displays information such as internal battery status, external supply voltage, logger current draw, Serial Number, firmware version, SD Card Status, Measurement interval, Data reporting options and correction factors. The utility software enables the Sap Flow Meter to be used in manual mode. This provides the ability to evaluate the efficacy of pulse intervals by viewing the raw measured temperatures on screen. Subsequent reports can then be viewed detailing the the duration of time the heat pulse required to deliver the exact amount of heat energy in Joules, the temperature rise following the previous heat pulse, temperature ratios between measurement points, sap velocity or sap flow.
Combined Instrument Software Interface - Sap Flow

Data Analysis

Data can be manually processed using a spreadsheet program such as Excel to open the comma separated value (CSV) file provided by the Sap Flow Meter. More powerful and immediate processing can be achieved by directly importing the data file into the Sap Flow Tool Software. Thus providing instant 2 dimensional and 3D graphing of the raw heat pulse velocity and processing of sap velocity and sap flux. The entire data set can be instantly reprocessed if correction factors require modification or additional information becomes available.
Sap Flow Rate



Output Options Raw Temperatures: °C
Heat Pulse Velocity: cm hr-1
Sap Velocity: cm hr-1
Sap Flow: cm3 hr-1 (Litres hr-1)
Range -100 to +100 cm hr-1
Resolution 0.01 cm hr-1
Accuracy 0.5 cm hr-1
Measurement Duration 120 seconds
Heat Pulse User Adjustable: 20 Joules (default) approx. Equivalent to a 2.5 second heat pulse duration, auto scaling.
Logging Interval User Adjustable: Minimum interval, 3 minutes, recommended minimum 10 minutes.


Computer Interface USB, Wireless RF 2.4 GHz
Data Storage MicroSD Card
Memory Capacity Up to 16GB, 8GB MicroSD card included.


Needle Diameter 1.3 mm
Needle Length 35 mm
Measurement Positions 2 per measurement needle
Measurement Spacings 7.5 mm and 22.5 mm from the needle tip
Dimensions L x W X D 170 x 80 x 35 mm
Weight 400 g



Temperature Range -10 to 50°C
R/H Range 0-99%


Internal Battery Specifications
950mAh Lithium Polymer, 4.20 Volts fully charged
External Power Requirements
Bus Power 8-30 Volts DC, non-polarised, current draw is 190mA maximum at 17 volts per logger
USB Power 5 Volts DC
Internal Charge Rate
Bus Power 60mA – 200mA Variable internal charge rate, maximum charge rate of 200mA active when the external voltage rises above 16 Volts DC
USB Power 100mA fixed charge rate
Internal Power Management
Fully Charged Battery 4.20 Volts
Low Power Mode 3.60 Volts – Instrument ceases to take measurements
Discharged Battery 2.90 Volts – Instrument automatically switches off at and below this voltage when no external power connected.
Battery Life varies
  • With a recommended power source connected, operation can be continuous.
  • Approximately 1.5 days with a heat pulse of 50 Joules and a measurement interval of 30 minutes – no external power present to recharge battery.
  • Carbon and Water Monitoring
    How can environmental research and monitoring help manage productivity, biodiversity and ecosystem services for a growing population?
  • CH24 - 24 Volt Power Supply
    The CH24 is a 100 - 240Volts AC Mains to 24Volts DC power supply adapter; capable of outputting up to 2.5Amps. For most ICT Instruments.
  • ICT CIS - Cloud Data Analysis and Display
    The ICT CIS and DataView.
  • ICT Universal Telemetry Hub
    ICT Universal Telemetry Hub
  • SFM-SK1 Installation Kit
    SFM-SK1 Installation kit
  • SFM-DR Dremel 8000
    Dremel 8000 for SFM1 installation
  • DR Dremel 800 Chuck Collet
    This DR Dremel 800 Collet is necessary in order that the small diameter drill bits, as used for the installation of the SFM1 needles, can be inserted into the SFM-DR Dremel Drill Chuck.
  • SFT1 Sap Flow Tool
    Sap Flow Tool software for HFD and HRM. Single License. Unlimited access to any number HRM or HFD datasets. Configured to analyse HRMx, CHPM, Tmax data from the SFM Sap Flow Meter. Visualise PSY1, soil moisture, and meteorological data.
  • SP22 - 20 Watt Solar Panel
    SP22 - 20 Watt Solar Panel with 4m cable suitable for powering our SFM1, PSY1, HFD, SOM1, SMM1 etc products.
  • The HRM Test Block
    The HRM Sap Flow Meter Test Block is a functional verification standard for use with the HRM Sap Flow Meter.

Ambrose, A. R., Sillett, S. C., Koch, G. W., Van Pelt, R., Antoine, M. E., & Dawson, T. E. (2010). Effects of height on treetop transpiration and stomatal conductance in coast redwood (Sequoia sempervirens). Tree Physiology, 30(10), 1260–1272. https://doi.org/10.1093/treephys/tpq064

Bader, M. K.-F., & Leuzinger, S. (2019). Hydraulic Coupling of a Leafless Kauri Tree Remnant to Conspecific Hosts. iScience. https://doi.org/10.1016/j.isci.2019.05.009

Barron-Gafford, G. A., Sanchez-Cañete, E. P., Minor, R. L., Hendryx, S. M., Lee, E., Sutter, L. F., Tran, N., Parra, E., Colella, T., Murphy, P. C., Hamerlynck, E. P., Kumar, P. and Scott, R. L. (2017), Impacts of hydraulic redistribution on grass–tree competition vs facilitation in a semi-arid savanna. New Phytologist, 215(4), 1451–1461. https://doi.org/10.1111/nph.14693

Bleby, T. M., Burgess, S. S., & Adams, M. A. (2004). A validation, comparison and error analysis of two heat-pulse methods for measuring sap flow in Eucalyptus marginata saplings. Functional Plant Biology, 31(6), 645-658. http://www.publish.csiro.au/paper/FP04013.htm

Buckley, T. N., Turnbull, T. L., Pfautsch, S., & Adams, M. A. (2011). Nocturnal water loss in mature subalpine Eucalyptus delegatensis tall open forests and adjacent E. pauciflora woodlands. Ecology and evolution, 1(3), 435-450. http://onlinelibrary.wiley.com/doi/10.1002/ece3.44/pdf

Buckley, T. N., Turnbull, T. L., & Adams, M. A. (2012). Simple models for stomatal conductance derived from a process model: Cross-validation against sap flux data. Plant, Cell & Environment, 35(9), 1647–1662. https://doi.org/10.1111/j.1365-3040.2012.02515.x

Buckley, T. N., Turnbull, T. L., Pfautsch, S., Gharun, M., & Adams, M. A. (2012). Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker. Forest Ecology and Management, 270, 1–10. https://doi.org/10.1016/j.foreco.2012.01.008

Burgess, S. S., Adams, M. A., Turner, N. C., Beverly, C. R., Ong, C. K., Khan, A. A., & Bleby, T. M. (2001). An improved heat pulse method to measure low and reverse rates of sap flow in woody plants. Tree Physiology, 21(9), 589–598. https://doi.org/10.1093/treephys/21.9.589

Burgess, S. S. O., M. A. Adams, N. C. Turner, C. K. Ong, A. A. H. Khan, C. R. Beverly and T. M. Bleby (2001) Corrections: An improved heat pulse method to measure low and reverse rates of sap flow in woody plants. Tree Physiology, 21(16), 1157. doi:10.1093/treephys/21.16.1157 http://treephys.oxfordjournals.org/content/21/16/1157.full.pdf

Carbone, M. S., Park Williams, A., Ambrose, A. R., Boot, C. M., Bradley, E. S., Dawson, T. E., … & Still, C. J. (2013). Cloud shading and fog drip influence the metabolism of a coastal pine ecosystem. Global Change Biology, 19(2), 484–497. https://doi.org/10.1111/gcb.12054

De Groote, S. (2013). Impact of dew and rain on the water relations of the mangrove species Avicennia marina (Forssk.) Vierh (Doctoral dissertation, Master’s thesis, University Ghent, Faculty of Bioscience Engineering). Click to view Paper

Doronila, A. I. (2015). Performance Measurement Via Sap Flow Monitoring of Three Eucalyptus Species for Mine Site and Dryland Salinity Phytoremediation. International Journal of Phytoremediation, 17(2), 101–108. https://doi.org/10.1080/15226514.2013.850466

Downey A., Winter, W., Cull, P. (2013). Smart trees, smart kids – empowering a generation through the science of sap flow. ICT International. Downey et al Smart Trees Smart Kids – Empowering a Generation through the Science of Sap Flow

Drake, P. L., Coleman, B. F., & Vogwill, R. (2013). The response of semi-arid ephemeral wetland plants to flooding: Linking water use to hydrological processes. Ecohydrology, 6(5), 852–862. https://doi.org/10.1002/eco.1309

Eliades, M., Bruggeman, A., Djuma, H., and Lubczynski, M. W. (2018). Tree Water Dynamics in a Semi-Arid, Pinus brutia Forest. Water, 10(8), 1039. https://doi.org/10.3390/w10081039

Eliades, M., Bruggeman, A., Lubczynski, M. W., Christou, A., Camera, C., Djuma, H. (2017). The water balance components of Mediterranean pine trees on a steep mountain slope during two hydrologically contrasting years. Journal of Hydrology, 562, 712–724. https://doi.org/10.1016/j.jhydrol.2018.05.048

Eller, C. B., Lima, A. L., & Oliveira, R. S. (2013). Foliar uptake of fog water and transport belowground alleviates drought effects in the cloud forest tree species, Drimys brasiliensis (Winteraceae). New Phytologist, 199(1), 151–162. https://doi.org/10.1111/nph.12248

Falge, E., & Meixner, F. X. (2008). Validation of a 3D gas exchange model for a Picea abies canopy in the Fichtelgebirge, Germany. In Geophys. Res. Abstr (Vol. 10). Download PDF.

Fuchs, S., Leuschner, C., Link, R., Coners, H., Schuldt, B. (2017). Calibration and comparison of thermal dissipation, heat ratio and heat field deformation sap flow probes for diffuse-porous trees. Agricultural and Forest Meteorology, 244–245, 151–161. https://doi.org/10.1016/j.agrformet.2017.04.003

Gharun, M., Turnbull, T. L., & Adams, M. A. (2013). Stand water use status in relation to fire in a mixed species eucalypt forest. Forest Ecology and Management, 304, 162–170. https://doi.org/10.1016/j.foreco.2013.05.002

Gharun, M., Turnbull, T. L., Pfautsch, S., & Adams, M. A. (2015). Stomatal structure and physiology do not explain differences in water use among montane eucalypts. Oecologia, 177(4), 1171–1181. https://doi.org/10.1007/s00442-015-3252-3

Mitchell, P. J., Veneklaas, E., Lambers, H., & Burgess, S. S. (2009). Partitioning of evapotranspiration in a semi-arid eucalypt woodland in south-western Australia. Agricultural and Forest Meteorology, 149(1), 25–37. https://doi.org/10.1016/j.agrformet.2008.07.008

Palmer, A. R., Fuentes, S., Taylor, D., Macinnis‐Ng, C., Zeppel, M., Yunusa, I., & Eamus, D. (2010). Towards a spatial understanding of water use of several land-cover classes: An examination of relationships amongst pre-dawn leaf water potential, vegetation water use, aridity and MODIS LAI. Ecohydrology, 3(1), 1–10. https://doi.org/10.1002/eco.63

Patankar, R., Quinton, W. L., Hayashi, M., & Baltzer, J. L. (2015). Sap flow responses to seasonal thaw and permafrost degradation in a subarctic boreal peatland. Trees, 29(1), 129–142. https://doi.org/10.1007/s00468-014-1097-8

Pfautsch, S., Dodson, W., Madden, S., & Adams, M. A. (2015). Assessing the impact of large-scale water table modifications on riparian trees: A case study from Australia. Ecohydrology, 8(4), 642–651. https://doi.org/10.1002/eco.1531

Pfautsch, S., Keitel, C., Turnbull, T. L., Braimbridge, M. J., Wright, T. E., Simpson, R. R., … & Adams, M. A. (2011). Diurnal patterns of water use in Eucalyptus victrix indicate pronounced desiccation–rehydration cycles despite unlimited water supply. Tree Physiology, 31(10), 1041–1051. https://doi.org/10.1093/treephys/tpr082

Pfautsch, S., Peri, P. L., Macfarlane, C., van Ogtrop, F., & Adams, M. A. (2014). Relating water use to morphology and environment of Nothofagus from the world’s most southern forests. Trees, 28(1), 125–136. https://doi.org/10.1007/s00468-013-0935-4

Reddy, K. S., Sekhar, K. M., Reddy, A. R. (2017). Genotypic variation in tolerance to drought stress is highly coordinated with hydraulic conductivity–photosynthesis interplay and aquaporin expression in field-grown mulberry (Morus spp.). Tree Physiology, 37(7), 926–937. https://doi.org/10.1093/treephys/tpx051

Resco de Dios, V., Díaz‐Sierra, R., Goulden, M. L., Barton, C. V., Boer, M. M., Gessler, A., … & Tissue, D. T. (2013). Woody clockworks: Circadian regulation of night-time water use in Eucalyptus globulus. New Phytologist, 200(3), 743–752. https://doi.org/10.1111/nph.12382

Rosado, B. H., Oliveira, R. S., Joly, C. A., Aidar, M. P., & Burgess, S. S. (2012). Diversity in nighttime transpiration behavior of woody species of the Atlantic Rain Forest, Brazil. Agricultural and Forest Meteorology, 158–159, 13–20. https://doi.org/10.1016/j.agrformet.2012.02.002

Staudt, K., Serafimovich, A., Siebicke, L., Pyles, R. D., & Falge, E. (2011). Vertical structure of evapotranspiration at a forest site (a case study). Agricultural and Forest Meteorology, 151(6), 709–729. https://doi.org/10.1016/j.agrformet.2010.10.009

Thom, J. K., Szota, C., Fletcher, T. D., Grey, V., Coutts, A. M., & Livesley, S. J. (2019). Transpiration and the water balance of tree-based stormwater control measures. Novatech 2019: Urban Water Planning and Technologies for Sustainable Management. Presented at the Novatech 2019, Lyon, France. Retrieved from www.novatech.graie.org/documents/auteurs/1D24-096THO.pdf

Van de Wal, B. A., Guyot, A., Lovelock, C. E., Lockington, D. A., & Steppe, K. (2015). Influence of temporospatial variation in sap flux density on estimates of whole-tree water use in Avicennia marina. Trees, 29(1), 215–222. https://doi.org/10.1007/s00468-014-1105-z

Zeppel, M. J., Lewis, J. D., Medlyn, B., Barton, C. V., Duursma, R. A., Eamus, D., … & Tissue, D. T. (2011). Interactive effects of elevated CO2 and drought on nocturnal water fluxes in Eucalyptus saligna. Tree Physiology, 31(9), 932–944. https://doi.org/10.1093/treephys/tpr024


Japanese Research Articles (written in Japanese)

Takeuchi, S., Matsuda, A., & Nishi, Y. (2014). Sap flow movement on Magnolia grandiflora L. and Acer palmatum Thunb. after transplanting for two years. Journal of the Japanese Society of Revegetation Technology, 40(1), 60–65. https://doi.org/10.7211/jjsrt.40.60

Takeuchi, S., Morita, K., Kishimoto, T., & Shinozaki, K. (2012). Sap Flow movement on Magnolia grandiflora L. through the process of transplanting work. Journal of the Japanese Society of Revegetation Technology, 38(1), 27–32. https://doi.org/10.7211/jjsrt.38.27

Takeuchi, S., Takahashi, R., & Iida, S. (2016). Growth diagnosis of a transplanted tree based on sap flow measurement: A case study of Magnolia grandiflora L. for four years after transplantation. Journal of the Japanese Society of Revegetation Technology, 42(1), 110–115. https://doi.org/10.7211/jjsrt.42.110