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TEROS 12 Tech Specs
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Technical Specifications

Volumetric Water Content (VWC)
Range
Mineral Soil Calibration: 0.00–0.70 m3/m3
Soilless Media Calibration: 0.0–1.0 m3/m3
Apparent Dielectric Permittivity (εa): 1 (air) to 80 (water)
NOTE: The VWC range is dependent on the media the sensor is calibrated to. A custom calibration will accommodate the necessary ranges for most substrates.
Resolution
0.0010 m3/m3
Accuracy
Generic Calibration: ±0.03 m³/m³ (±3.00% VWC) typical in mineral soils that have solution EC <8,000 μS/cm
Medium Specific Calibration: ±0.01–0.02 m³/m³ in any porous medium
Apparent Dielectric Permittivity (εa): 1–40 (soil range) , ±1 εa (unitless) 40–80, 15% of measurement
Measurement Specifications
Temperature
Range: −40 to +60 °C
Resolution: 0.10 °C
Accuracy: ±0.5 °C from −40 to 0 °C
±0.3 °C from 0 to +60 °C
Dielectric Measurement Frequency
70 MHz
Bulk Electrical Conductivity (EC)
Range: 0–20,000 μS/cm (bulk)
Resolution: 1 μS/cm
Accuracy: +/- (5% + 10 μS/cm) from 0–10,000 μS/cm
+/- 8% from 10,000–20,000 μS/cm
Measurement Volume
Communication Specifications
Output
DDI serial or SDI-12 communications protocol
Data Logger Compatibility
METER ZL6, EM60, and Em50 data loggers or any data acquisition system capable of 4.0- to 15-VDC power and serial or SDI-12 communication
See compatibility chart
Physical Specifications
Dimensions
Length: 9.4 cm (3.70 in)
Width: 2.4 cm (0.95 in)
Height: 7.5 cm (2.95 in)
Needle Length
5.5 cm (2.17 in)
Operating Temperature Range
Minimum: -40.00 °C
Typical: NA
Maximum: 60.00 °C
NOTE: Sensors may be used at higher temperatures under certain conditions; Contact Customer Support for assistance.
Cable Length
5 m (standard)
75 m (maximum custom cable length)

NOTE: Contact Customer Support if a nonstandard cable length is needed.
Cable Diameter
0.165 ±0.004 in (4.20 ± 0.10mm) with minimum jacket of 0.030 (0.760 mm)
Connector Types
Stereo plug connector or stripped and tinned wires
Stereo Plug Connector Diameter
3.5 mm
Conductor Gauge
22-AWG / 24-AWG drain wire
Electrical and Timing Characteristics
Supply Voltage (VCC to GND)
Minimum: 4.0 VDC
Typical: NA
Maximum: 15.0 VDC
Digital Input Voltage (Logic High)
Minimum: 2.8 V
Typical: 3.6 V
Maximum: 5.0 V
Digital Input Voltage (Logic Low)
Minimum: -0.3 V
Typical: 0.0 V
Maximum: 0.8 V
Digital Output Voltage (Logic High)
Minimum: NA
Typical: 3.6 V
Maximum: NA
Power Line Slew Rate
Minimum: 1.0 V/ms
Typical: NA
Maximum: NA
Current Drain (During 25-ms Measurement)
Minimum: 3.0 mA
Typical: 3.6 mA
Maximum: 16.0 mA
Current Drain (While Asleep)
Minimum: NA
Typical: 0.0 mA
Maximum: NA
Power Up Time (DDI Serial)
Minimum: 80 ms
Typical: NA
Maximum: 100 ms
Power Up Time (SDI-12)
Minimum: NA
Typical: 245 ms
Maximum: NA
Power Up Time (SDI-12, DDI Serial Disabled)
Minimum: 145 ms
Typical: 155 ms
Maximum: 165 ms
Measurement Duration
Minimum: 25 ms
Typical: NA
Maximum: 150 ms
Other
Compliance
Manufactured under ISO 9001:2015
EM ISO/IEC 17050:2010 (CE Mark)
2014/30/EU and 2011/65/EU
EN61326-1:2013 and EN55022/CISPR 22
GSA