Digital SDI Soil Moisture Sensor

Digital SDI Soil Moisture Sensor



The Digital TDT® Soil Moisture, Temperature, and Conductivity Sensor represents a revolutionary advance in the irrigation industry and is now available as a research tool. The digital sensor is a very effective tool to log moisture data for a variety of applications.


  • Reads the absolute volumetric water content
  • Reads soil temperature and soil conductivity
  • Industry’s most accurate and stable soil moisture sensor
  • Operates accurately in all environmental soil conditions in which crops will grow
  • Large 100 ml soil sample volume
  • No maintenance, simple installation
  • Sturdy construction to ensure long-term reliability in any soil
  • Moisture readings remain stable as soil salinity and fertilizer content change
  • Moisture readings remain stable as soil temperature changes


Physical Characteristics
  Durable housing and waterproof epoxy construction
  Width: 2 1/8″ (5.4 cm)
  Height: 9/16″ (1.4 cm)
  Length: 8″ (20.3 cm)
  Wire Length: 25′ (7.62 m)
  Weight (with 3m cable): 220g
  • Composition (exposed to soil)
Type 304 Stainless Steel, crystalline-epoxy, polyethylene (insulation)
  • Cable Type and Length
3 conductor, 18 Ga. PE sheath, 6 meter length
  • Operating Temperature Range
1°C to 50°C
  • Storage Temperature Range
-20°C to 75°C
  • Lightning and Surge Protection
6kV @ 3kA, 8/50us
  • Volumetric Water Content Range
0 to 100%
  • Resolution
0.06% VWC
  • Absolute WVC Accuracy
+/-2% (typical)
  • VWC Temperature Stability
+/-1% of full scale 1°C to 50°C
  • VWC Soil EC Stability
+/-1% of full scale 0 to 5 dS/m Bulk EC
  • Temperature Reporting Accuracy
+/-2C, 0 to 70°C
  • EC Reporting Acccuracy
+/-0.2 dS/m, 0 to 5.0 dS/m BEC
  • Technology
Waveform Digitizing Time Domain Transmissometer
  • Effective Acquisition Bandwidth
200 Giga-samples/sec.
  • Propagation time resolution
5 ps
  • Waveform Propagation resolution
1.5mm in air, 0.16mm in water
  • Waveguide Length
  • Permittivity to VWC Calculation
Modified Dielectric Mixing model
  • Propagated Waveform Bandwidth
>2 GHz
  • Communications Protocol
SDI-12 Revision 1.3
  • Maximum Cable Length
60 meters (200ft)
  • Maximum Devices per Cable
  • Operating Voltage Range
4-15 VDC
  • Listening/Sleep Mode Current
15 uA (18 uA at 50C)
  • Communications Current
2.5 mA typical, 4 mA max
  • Read Moisture Comm Time
425 ms total for each read cycle
  • Moisture Sense Current
30 mA at 12 VDC input voltage
  55 mA at 6 VDC input voltage
  75 mA at 4 VDC input voltage
  • Moisture Sense Time
450 ms for each moisture sensing operation