Tech Specs

TEROS 21 Tech Specs


Measurement Specifications
Water Potential
Range: 0 to −100,000 kPa (1.70 to 6.00 pF)
Resolution: 0 kPa
Accuracy: ±(10% of reading + 2 kPa) from −100 to −5 kPa
NOTE: TEROS 21 Gen 2 can read up to 0 kPa when on a wetting path. The air entry of the soil limits the performance of the sensor to 0 kPa on the drying curve.
NOTE: TEROS 21 is not well calibrated beyond -100 kPa. For more information on using the TEROS 21 beyond this range, see Section 3.3.3 in the user manual
Range: -40.00 – 60.00 °C
Resolution: 0.10 °C
Accuracy: ±1.00 °C
Dielectric Measurement Frequency
70 MHz
Communication Specifications
DDI serial or SDI-12 communication protocol
Data Logger Compatibility
METER ZL6, EM60, and Em50 data loggers or any data acquisition system capable of 3.6- to 15-VDC power and serial or SDI-12 communication
Physical Specifications
Length: 9.6 cm (3.8 in)
Width: 3.5 cm (1.4 in)
Height: 1.5 cm (0.6 in)
Sensor Diameter
3.2 cm (1.3 in)
Operating Temperature Range
Minimum: -40.00 °C
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.
Connector Types
3.5-mm stereo plug connector or stripped and tinned wires
Electrical and Timing Characteristics
Supply Voltage (VCC to GND)
Minimum: 3.6 VDC
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
Power Line Slew Rate
Minimum: 1.0 V/ms
Current Drain (During Measurement)
Minimum: 3.0 mA
Typical: 5.0 mA
Maximum: 16.0 mA
Current Drain (While Asleep)
Minimum: 0.0 mA
Power Up Time (DDI Serial)
Maximum: 50 ms
Power Up Time (SDI-12)
Typical: 175 ms
Measurement Duration
Typical: 175 ms
Product Awards
EM ISO/IEC 17050:2010 (CE Mark)
EN 55011:2016 / A1:2017 (RCM Mark)

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