Fruit Dendrometer

Dendrometer for fruit growth measurement

  • Attaches to the plant in seconds
  • Lightweight and will not damage the fruit or trunk
  • Installation resistant to wind and rain
  • Sizes to accommodate different sizes of fruit and trunks
  • Stable and adjustment-free operation
  • Real-time measurement of fruit and trunk growth
  • Swiss design and manufacture


Technical data


The fruit dendrometer measures the following:

  • Diameter
  • Temperature

The data is transferred via an I2C-bus interface. Multiple dendrometers as well as other sensors may be combined on the same bus and share a single radio transceiver hub to transfer data for monitoring and analysis.

There are two categories of I2C registers within the dendrometer:

  1. Ram registers: values which change often and are not saved after a reset.
  2. Flash registers: configuration values which are saved after a reset.

Writing to and reading from registers

Configurations registers are read-only by default.  ENABLE_MODE_CONFIG must be set to enable write-mode.

Packet format

Register Mapping


Address Name Description Read/Write
0x00 DIAMETER_OUTPUT_L low byte diameter 0.01 mm/LSB R
0x01 DIAMETER_OUTPUT_H high byte diameter 0.01 mm/LSB R
0x02 TEMPERATURE_OUTPUT_L low byte temperature 0.1℃/LSB R
0x03 TEMPERATURE_OUTPUT_H high byte temperature 0.1℃/LSB R
0x06 START_MEAS write 1 to start measurement. always 0 when read R/W
0x7F ENABLE_MODE_CONFIG when set all addresses may be written W


Address Name Description Read/write
0x8A CALIBRATION_OFFSET_L low byte offset on the diameter 0.01 mm/LSB R
0x8B CALIBRATION_OFFSET_H high byte offset on the diameter 0.01 mm/LSB R
0x8C TEMPERATURE_OFFSET_L low byte offset on the temperature 0.1℃/LSB R
0x8D TEMPERATURE_OFFSET_H high byte offset on the temperature 0.1℃/LSB R
0x8E DIAMETER_LIMIT_LOW_L low byte low saturation of the diameter 0.01 mm/LSB R/W
0x8F DIAMETER_LIMIT_LOW_H high byte low saturation of the diameter 0.01 mm/LSB R/W
0x90 DIAMETER_LIMIT_HIGH_L low byte high saturation of the diameter 0.01 mm/LSB R/W
0x91 DIAMETER_LIMIT_HIGH_H high byte high saturation of the diameter 0.01 mm/LSB R/W

The fruit dendrometer comprises:

  • Spring-loaded arm-assembly with integral sensors and signal conditioning
  • Screened cable
  • 4-pole waterproof connector (to connect to our transceiver unit or a bus-extender


Temperature Diameter
Units of measurement Degree Celsius mm
Resolution 0.1°C 0.01 mm
Precision +- 0.3°C +-0.05 mm
Range of measurement 0°C to 65°C 19mm to 90mm


  • 3.3V
  • 7.4mA (operating)

Initial configuration

Dendrometers are all delivered with a default I2C address. To combine multiple dendrometers on the same bus each needs to be re-programmed with a unique I2C address; this configuration may either be made at the time of ordering or programmed on-site prior to deployment.

Making measurements

To make a measurement

  1. Write 1 in the START_MEAS register
  2. Wait 50 ms for the measurement to be made
  3. Read the measurement (diameter, temperature) in the output register