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HD3901-Leaf Wetness Sensor

Make: Delta ohm                                      Model: HD3901
✅ HD3901 leaf wetness sensor detects the presence of condensation on its sensitive surface and has been designed to reproduce in an extremely accurate way the thermodynamic behaviour of a leaf.
✅ Measurand : Leaf Wetness
✅ Sensor Type : Capacitive
✅ Signal Output : Two analog outputs (one output for each of the two sensitive surfaces).
✅ Supplied With : Cable, Factory test/ Calibration Certificates.

HD3901-Leaf Wetness Sensor:

The HD3901 leaf wetness sensor detects the presence of condensation on its sensitive surface and has been designed to reproduce in an extremely accurate way the thermodynamic behavior of a leaf. Leaf wetness degree is basic information in the agricultural and floriculture fields to determine the most appropriate phytosanitary treatment to prevent mold and fungal infections in general that can affect the plants and crops in the presence of condensation on the leaves.

The double-sensitive surface allows for determining the wetness degree both on the top and on the bottom of the leaf, an important feature to get accurate indications, being that the two sides of the leaf have different drying times. In order to ensure a long lifespan of the sensor, the surface of the sensor is specially treated to resist both the atmospheric agents and the chemical agents present in pesticide products.

The sensor is factory calibrated and does not need to be calibrated by the user. With a fixed 5 (HD3901.5) or 10 (HD3901.10) m connecting cable, the output is 0.5… 3 V analog voltage. Power supply: 5—18 Vdc.


On the sensitive surface of the sensor, two grid-shaped electrodes are placed. The sensor detects the change of the dielectric constant between the two electrodes caused by the presence of water drops on the surface.
Thanks to its operation principle, the sensor HD3901 is able to detect even the presence of small water droplets, unlike common sensors which are based on the resistance or conductivity measurement, which require that the drop of water to be detected between the two electrodes has a minimum size.
The construction materials and the white colour of the sensitive-surface have been chosen to simulate, in the most reliable way as possible, the thermal and radiative properties of a real leaf.
The 0.5 … 3 V analog voltage output corresponds to the degree of wetness 0 … 100%. The degree (percentage) of wetness indicates how much sensitive surface is covered by the water compared to the total surface of the sensitive area.

Application and features of HD3901-Leaf Wetness Sensor:



✅ Agriculture
✅ Floriculture
✅ Study of phytopathogen models forecasting
✅ Reliable reproduction of the thermodynamic properties of a leaf
✅ Capacitive measurement principle for the accurate detection of even the smallest drops of water
✅ Double sensitive surface
✅ High resistance to chemical and atmospheric agents
✅ It can be installed in the field thanks to the IP67 degree of protection

Delta ohm



Weight (Mass)

About 100 g (including the 5 m cable)


61 x 115 x 11 mm (excluding cable). Width of the sensor 1.6 mm

Measurement Principle



Analog (0.5…3 V)

Power Supply

5…18 Vdc


± 5%

Power Consumption

< 1 mA

Measuring Range

0…100% of leaf area wetness

Operating Environment

-30…+60 °C

Protection Degree



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