Using the Meter EC-5 Soil Moisture Probe in Biomet Systems

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The Meter (formerly Decagon) EC-5 soil moisture probe measures moisture content in soils and provides data to a datalogger using analog signals. This document describes basic installation and operating guidelines for using the EC-5 in LI-COR biomet data acquisition systems in a Basic biomet program or custom program. Refer to the manufacturer's documentation for more information:

ECH2O EC-5 Specifications:
Measurement Range: 0 to saturation
Operating Temp. -40 to +60 °C
Accuracy: Better than 0.03 m3/m3 for all soils, up to 8 dS/m
Response Time: 10 ms
Power Requirements: 2.5-3.5 VDC @ 10 mA
Output Signal: 10-40% of excitation

Siting the Soil Moisture Probes

Place the probes in undisturbed soil that is representative of the site. The Basic program supports two probes.

Installing the Soil Moisture Probes

Dig a hole to the desired depth. Orient the flat side of the sensor perpendicular to the soil surface to minimize the effects of water. Push the prongs into undisturbed soil at the bottom or side of the hole. Be sure there are no air gaps and that the sensor is in complete contact with soil. Be sure the prongs are covered completely up to the over-molding. Backfill the hole to match the bulk density of the soil.

Wiring the Soil Moisture Probes to the Datalogger

EC-5 probes are supported by the Basic program and custom programs. The following assignments apply to the Basic program.

Description Wire Color Probe 1 Probe 2
Signal Orange or Red A7 A8
Ground Bare G4 G4
Power Brown or White A15EXC A16EXC

Retrieving Data

The SmartFlux System will log these data in compressed files for processing by EddyPro Software and evaluation by Tovi Software. Data are stored on the USB drive on the SmartFlux System. Refer to the Data Acquisition System instruction manual for details.


The ECH2O EC-5 probe is a low maintenance sensor and little care is required as long as the sensor is performing as expected. If the sensor is providing questionable data:

  • Check the connections to the datalogger and ensure that they are correct and secure.
  • Check the cables for damage.
  • Ensure that the datalogger has an adequate power supply.