sensor for soil moisture and temperature | HD 3910

general information:

The probes HD3910.1 (two electrodes) and HD3910.2 (three electrodes) measure
the soil volumetric water content (VWC) by using a capacitive measurement principle

which allows fast measurements in the field and with minimal invasiveness.

The three-electrode probe HD3910.2 is particularly suitable for the measurement in

small volumes, for example for cultivations in pots.

The probes are factory-calibrated and do not require any further calibration by the

end user.

The circuit board is protected inside a housing made of plastic material and sealed
with epoxy resin which allows achieving reliable measurements even in harsh

environmental conditions.

The version with RS485 digital output with MODBUS-RTU protocol allows the use of
even very long connection cables. It can be connected to the data loggers HD32MT.1

and HD32MT.3 or to any other data logger with RS485 MODBUS-RTU input.

The version with SDI‑12 digital output is compatible with version 1.3 of the protocol
and can be connected to the data logger HD32MT.3 or to any other data logger with

SDI‑12 input.

The version with analog output has two 0.5…3 V standard voltage outputs: one for
the volumetric water content and one for the temperature. On request, 0…2.5 V,

0…5 V or 0…10 V outputs.

The probes are equipped with a fixed cable, 5 or 10m standard length, with open
wires at the end.

measurement of the soil volumetric water content with 2 electrodes (HD3910.1) or 3 electrodes (HD3910.2) for restricted volumes
measurement of the soil temperature
various output options available (depending on model): digital RS485 with MODBUS-RTU protocol, digital SDI‑12 or analog voltage
Accurate and stable measurements over time
ingress protection IP 67
minimal invasiveness in the soil
easy to install

applications:

agriculture
hydrology
geology

specifications:

volumetric water content
measuring principle:	capacitive
measuring range:	0 % to 100 % VWC (60 % for versions with analog output)
resolution:	0.1 %
accuracy (at 23°C):	±3 % between 0 and 50 % VWC (standard mineral soil, EC <5 mS/cm)
measuring volume:	∅ = 60 mm x H = 150 mm for 2-electrode probe ∅ = 40 mm x H = 110 mm for 3-electrode probe
sensor operating temperature:	-40°C to +60°C

temperature
sensor:	NTC 10 kW at +25°C
measuring range:	-40°C to +60°C
resolution:	0.1°C
accuracy:	±0.5°C
long-term stability:	0.1°C / year

power supply:	• 3.6 to 30 V DC for versions with 0 to 2.5 V analog output • 5 to 30 V DC for versions with RS485 output and versions with 0.5 to 3 V analog output • 6 to 30 V DC for versions with SDI‑12 output • 7 to 30 VDC for versions with 0 to 5 V analog output • 12 to 30 V DC for versions with 0 to 10 V analog output
consumption:	• version with RS485 output: 2 mA average / 15 mA peak at 12 V DC • versions with analog output: 2.5 mA average / 15 mA peak at 12 V DC • versions with SDI‑12 output: 300 μA at 12 V DC in standby <15 mA at 12 V DC during measurement
output:	depending on model: • RS485 mit MODBUS‑RTU protocol • SDI‑12 • 0.5 to 3 V analog voltage (0.5 V = 0 % VWC or ‑40°C, 3 V = 60 % VWC or +60°C, minimal load resistance 10 kΩ)
materials:	handle: thermoplastic material and epoxy resin electrodes: epoxy glass, thickness 2 mm
connection:	fixed cable with open wires at the end, standard length 5 or 10 m
ingress protection:	IP 67
weight:	approx. 150 g (incl. 5 m cable)