The Dynamax Dynagage sap flow sensor consists of a flexible heater, a thermopile to measure radial heat loss, and differential thermocouple pairs to measure the axial temperature differences qu-qd.
All of these sensors and heater are mounted on a cork substrate and housed inside a white, reflective foam, thermal insulating collar. Once the sensor is installed on the stem surface, both the sensor and the stem sections above and below the sensor are completely covered by a heat insulator to minimise thermal perturbations caused by the ambient environment. Power is supplied continuously to the heater from a regulated DC power source.
The Dynagage Sap Flow Sensors are designed for measuring the sap flow, and thus the water consumption of plants. These energy balance sensors measure the amount of heat carried by the sap which is converted into Real-Time sap flow in grams or kilograms per hour. The sensors are non-intrusive and not harmful since the plants are heated up 1°C to 5°C typically.
The principles of heat balance sensors are scientifically proven and references exist for most major crops and many tree species. Unlike other methods, Dynagages require no calibration since sap flux is directly determined by the energy balance and rates of heat convection by the sap flow.
This technology is an affordable and practical way to measure the water use by plants of agricultural, economic and ecological importance. Plants in greenhouses, nurseries or natural environments can be measured with the same ease. Dynamax introduced the first sap flow sensor prototypes in 1988 and today offers a full range of sensors from 2mm up to 125mm.
|Model No||Diameter Min mm||Diameter Max mm||Height mm||2Input Volts||Typical Power watts||Number TC pairs||TCGap dx mm|
Baker, J. M., & Bavel, C. H. M. V. (1987). Measurement of mass flow of water in the stems of herbaceous plants. Plant, Cell & Environment, 10(9), 777–782. https://doi.org/10.1111/1365-3040.ep11604765
Baker, J. M., & Nieber, J. L. (1989). An analysis of the steady-state heat balance method for measuring sap flow in plants. Agricultural and Forest Meteorology, 48(1), 93–109. https://doi.org/10.1016/0168-1923(89)90009-9
Dugas, Wm. A. (1990). Comparative measurement of stem flow and transpiration in cotton. Theoretical and Applied Climatology, 42(4), 215–221. https://doi.org/10.1007/BF00865981
Grime, V. L., Morison, J. I. L., & Simmonds, L. P. (1995). Including the heat storage term in sap flow measurements with the stem heat balance method. Agricultural and Forest Meteorology, 74(1), 1–25. https://doi.org/10.1016/0168-1923(94)02187-O
Ham, J. M., Heilman, J. L., & Lascano, R. J. (1990). Determination of soil water evaporation and transpiration from energy balance and stem flow measurements. Agricultural and Forest Meteorology, 52(3), 287–301. https://doi.org/10.1016/0168-1923(90)90087-M
Heilman, J. L., Brittin, C. L., & Zajicek, J. M. (1989). Water use by shrubs as affected by energy exchange with building walls. Agricultural and Forest Meteorology, 48(3), 345–357. https://doi.org/10.1016/0168-1923(89)90078-6
Heilman, J. L., & Ham, J. M. (1990). Measurement of Mass Flow Rate of Sap in Ligustrum japonicum. HortScience, 25(4), 465–467. https://doi.org/10.21273/HORTSCI.25.4.465
Lascano, R. J., Baumhardt, R. L., & Lipe, W. N. (1992). Measurement of Water Flow in Young Grapevines Using the Stem Heat Balance Method. American Journal of Enology and Viticulture, 43(2), 159–165.
Steinberg, S. 1988, Dynamax Trunk-Flow Gauge Test – Technical Application Report 2. Insulation and Time of Attachment Test. Houston, Texas, Dynamax Inc.
Steinberg, S. L., Van Bavel, C. H. M., & McFarland, M. J. (1990). Improved Sap Flow Gauge for Woody and Herbaceous Plants. Agronomy Journal, 82(4), 851–854. https://doi.org/10.2134/agronj1990.00021962008200040037x
Steinberg, S., van Bavel, C. H., & McFarland, M. J. (1989). A gauge to measure mass flow rate of sap in stems and trunks of woody plants. Journal of the American Society for Horticultural Science, 114(3), 466–472.
Tan, C. S., & Buttery, B. R. (1995). Determination of the water use of two pairs of soybean isolines differing in stomatal frequency using a heat balance stem flow gauge. Canadian Journal of Plant Science, 75(1), 99–103. https://doi.org/10.4141/cjps95-016
van Bavel, M. G., & Ine, D. (1992, May). Stem flow gauges for measurement of crop water use. In National Irrigation Convention Proceedings, pp. 59-72.
van Bavel, M. G. (1995, April). Advances in microirrigation control by sap-flow monitoring systems. In Proc. Fifth Int’l Microirrigation Congress ASAE, Orlando, Florida. 2-6 April 1995 pp. 234-238.
Wiebel, J., & Chako, E. (1992, May). Sap flow, weight loss and transpiration in Mangosteen. In Loxton, Australia: CSIRO Div. of Hort., Darwin, Sap Flow Workshop, Loxton Res. Centre. S.A. 6 May 1992.