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DEN2 Point Dendrometer Meter

Datalogger configured for use with the ZN series Point Dendrometers.

Supports up to 4 Point Dendrometer Potentiometers.
0.01mm accuracy.
Self contained datalogger with internal lithium-polymer battery, requiring a power supply from a 22 or 11w solar panel for extended use.

For complete monitoring solutions, the DEN2 can used in combination with the SFM1 Sap Flow Meter, PSY1 Stem Psychrometer, LSM1 Light Sensor Meter or the ICT International automatic weather station.

Analogue Channels 5 Differential Channels. 4 available;
Automatic supply voltage monitoring wire links on Channel 1 for greater accuracy
Accuracy 0.01mm
Minimum Logging Interval 1 second
Delayed Start Suspend Logging, Customised Intervals
Sampling Frequency 10Hz


Communications USB, Wireless Radio Frequency 2.4 GHz
Data Storage MicroSD Card, SDHC & SDXC Compatible (FAT32 format)
Software Compatibility Windows 7, 8 & 8.1, 10 and Mac OS X
Data Compatibility FAT32 compatible for direct exchange of SD card with any Windows PC
Data File Format Comma Separated Values (CSV) for compatibility with all software programs
Memory Capacity Up to 16GB, 4GB microSD card included.

Operating Conditions

Temperature Range -40°C to +80°C
R/H Range 0-100%
Upgradable User Upgradeable firmware using USB boot strap loader function


Internal Battery Specifications
960mAh 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
Example A: With a recommended solar panel and/or recommended power source connected, operation can be continuous.
Example B: Power consumption is dependent on number and type of sensors connected, frequency of measurement and measurement duration

What is detected?

Diurnal stem radius fluctuations are mainly influenced by changes of the thickness of living tissues of the bark (mainly phloem cells). However, the xylem also undergoes size changes.
The radial size changes depend on water tensions inside the stem and have an influence on the hydration status of the bark. While water is withdrawn from the bark through transpiration during the daytime, at night the tissue is replenished. As a result of this cycle, the diameter decreases during the day and increases at night. Over a period of weeks and months, this diurnal rhythm is altered by growth. New layers of xylem cells irreversibly increase the radius, particularly during wet periods in the growing season. In winter, ice formations in the wood induce strong decreases of the stem radius.

Advantages in comparison to other products

• No disturbances by deformations of the dead outermost layer of the bark, induced by temperature and air-humidity (a general argument in favour of point dendrometers and against band dendrometers).
• Materials and electronic parts insensitive to temperature allow for more accurate measurements.
• The point of measurement is not influenced by the thread rods because it is neither in the vertical nor in the horizontal line of the anchor points.
• The application to different stem expositions allows a spatial resolution of stem radius fluctuations.
• Compatibility to most logging systems and easy to power with a stable 5V DC supply.
• Easy to mount.
• Minor disturbance of the tree stem.
• Weatherproof materials.
• Constructed, produced and tested by experts in tree physiology. Made in Switzerland.

Mounting principle

The electronic part of the dendrometer is mounted on a carbon fibre frame which is fixed to the stem by stainless steel thread rods implanted into the inactive heartwood.
Sensing rods are pressed lightly against the tree stem by a spring. The combination of weatherproof materials and a solid anchorage in the stem make it possible to precisely detect changes in the stem radius with a resolution of less than 1μm with an accurate logging system.

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De Schepper, V., & Steppe, K. (2010). Development and verification of a water and sugar transport model using measured stem diameter variations. Journal of Experimental Botany, erq018. 61(8): 2083 – 2099.

Ehrenberger, W., Rüger, S., Fitzke, R., Vollenweider, P., Günthardt-Goerg, M., Kuster, T., … & Arend, M. (2012). Concomitant dendrometer and leaf patch pressure probe measurements reveal the effect of microclimate and soil moisture on diurnal stem water and leaf turgor variations in young oak trees. Functional Plant Biology, 39(4), 297-305. doi:10.1071/FP11206: A – I.

Etzold, S., Ruehr, N. K., Zweifel, R., Dobbertin, M., Zingg, A., Pluess, P., … & Buchmann, N. (2011). The carbon balance of two contrasting mountain forest ecosystems in Switzerland: similar annual trends, but seasonal differences. Ecosystems, 14(8), 1289-1309.

Zweifel, R., Eugster, W., Etzold, S., Dobbertin, M., Buchmann, N., & Häsler, R. (2010). Link between continuous stem radius changes and net ecosystem productivity of a subalpine Norway spruce forest in the Swiss Alps. New Phytologist, 187(3), 819-830. doi: 10.1111/j.1469 – 8137.2010.03301.x.

Zweifel, R., Steppe, K., & Sterck, F. J. (2007). Stomatal regulation by microclimate and tree water relations: interpreting ecophysiological field data with a hydraulic plant model. Journal of Experimental Botany, 58(8), 2113-2131.

Zweifel, R., & Zeugin, F. (2008). Ultrasonic acoustic emissions in drought‐stressed trees–more than signals from cavitation?. New Phytologist, 179(4), 1070-1079.

Zweifel, R., Zimmermann, L., & Newbery, D. M. (2005). Modeling tree water deficit from microclimate: an approach to quantifying drought stress. Tree physiology, 25(2), 147-156.

Zweifel, R., Zimmermann, L., Tinner, W., Haldimann, P., Zeugin, F., Bangerter, S, Hofstet-ter, S, Conedera, M., Wohlgemuth, T., Gallé, A., Feller, U. & Newbery, D.M. (2006). Salgesch, Jeizinen, ihre Wälder und der globale Klimawandel. Nationaler For-schungsschwerpunkt Klima (NFS Klima), Universität Bern, Bern, p. 23.

Zweifel, R., Zimmermann, L., Zeugin, F., & Newbery, D. M. (2006). Intra-annual radial growth and water relations of trees: implications towards a growth mechanism. Journal of Experimental Botany, 57(6), 1445-1459.