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

DEX Fruit Dendrometers

The DEX20, DEX70, DEX100 and DEX200 are highly precise electronic dendrometers that measure the growth and size of plant stems and fruits. The DEX is a caliper-style device with a full bridge strain gage attached to a flexible arm. The output signal is recorded by a data logger or computer in real time. The millivolt sensor output shows both the diurnal and long term growth of the plant. DEX dendrometers have been used to test plants under conditions of water stress, elevated ozone and other atmospheric pollutants. Applications for screening plants for growth rate and stress tolerance are also common. The effects of environmental factors on the water balance of plants and stem size variations over time are easily monitored with a temperature compensated dendrometer.

  • Non-destructive
  • Real-time measurements
  • Adaptable to computer systems
  • Long-term measurements possible
  • Weatherproof and rugged for field study
  • Caliper body – milled alloy
  • Stainless steel flex band
  • Four balanced, temperature compensated strain gages
  • Electronics sealed and weatherproofed
  • Five clamping blocks provided, 3 for stems and 2 for fruits
  • Wires directly to datalogger
Units DEX20 DEX70 DEX100 DEX200
Measurement Range 5 – 25 10 – 70 25 – 100 95 – 200
Expansion Range 0 – 5 0 – 13 0 – 13 0 – 13
Dimensions (mm)
Length 65 102 155 263
Width 19 25.4 25.4 38
Height 38 51 76 153
Weight 55g 180g 230g 572g
Standard Clamping Blocks
Dimensions Set 1 19 x 19 x 6 25 x 25 x 9.5 25 x 25 x 9.5 25 x 25 x 905
Face Radius 5mm 70 mm 108 mm 200 mm
Dimensions Set 2 19 x 19 x 6 25 x 25 x 13 25 x 25 x 13
Face Radius 25 mm 5 mm/50 25 mm / 75
Optional Clamping Blocks
Dimensions 19 x 19 x 6 25 x 25 x 9.5 25 x 25 x 13 38 x 38 x 7
Spherical Radius 25 mm 70 mm 105 mm 500 mm
Environmental Specifications
Operating Range -10 to 50ºC -10 to 50ºC -10 to 50ºC -10 to 50ºC
Temperature Stability 0.0025mm/ºC 0.0025mm/ºC 0.0025mm/ºC 0.0025 mm/ºC
Accuracy Over 20ºC Range 0.050 mm 0.050 mm 0.050 mm 0.050 mm
Electrical Specifications
Signal Output Range ±5 mV ±5 mV ±2.5 mV ±2.5 mV
Output Sensitivity .5 mV/mm .22 mV/mm .13 mV/mm .05 mV/mm
Conversion Mult 2.0mm/mV 4.5mm/mV 7.7mm/mV 20mm/mV
Output Linearity ±01 mV/mm ±006 mV/mm ±004 mV/mm ±004 mV/mm
Electrical Noise Limit ±0.01 mV ±0.01 mV ±0.01 mV ±0.01 mV

The device is connected to a data logger, clamped onto a stem and suspended with mounting monofilament guides on the centre of gravity of each calliper arm, which is then attached to the tree or a staked plant. Velcro straps are provided for easy installation on trees or woody plants. The screw adjuster can be tightened to adjust the clamping blocks on opposite sides of the dendrometer. Thereafter, the change in stem size increases the output, which directly converts to the diameter increase past the point one recorded as the device’s zero point. A calibration multiplier may be loaded directly into a logger multiplier command, as well as the zero offset, thus giving readings directly in mm or inches instead of millivolts. Users may install optional shading and shielding to minimise heating and radiation effects.