Soil Water Potential Sensor TEROS-21

Don't settle for less
When it comes to measuring water potential (or soil suction), it is difficult to find a device that will meet your every need. You’re either forced to deal with lowered accuracy or high-maintenance hassles (not to mention getting soaked on cost).
You wouldn’t think taking such a simple reading would be so challenging. A true full-range sensor that’s low maintenance and low cost

The TEROS 21 water potential sensor is incredibly easy to use. It requires no maintenance, and it’s accurate enough for most applications.
In fact, the TEROS 21 provides an even more accurate soil moisture picture than measuring water content alone. A water content sensor only shows the percentage of water in the soil, but add a TEROS 21, and you’ll know if that water is available to plants and where it will move.
Plus, unlike water content, matric potential isn’t dependent on soil type, so you can compare moisture between different sites. Not only that, the TEROS 21 is surprisingly affordable, and the new Gen 2 version boasts an improved circuit, a more robust microprocessor, and an improved measurement range.
It now measures all the way from near saturation to air dry (−5 to −100,000 kPa) making it the word’s first true full range water potential sensor.

Broad soil applications. Dependable accuracy:
To say TEROS 21 is more accurate than competitor sensors doesn’t do it justice. That’s because unlike competitor models, we calibrate each and every sensor for you. To do this, we use a chamber system that allows the TEROS 21 matric potential sensor to come to a fixed water potential. We put sensors in silica flour, and by controlling the water potential, we’re able to set calibration points from -10 kPa to -80 kPa. The result: a long-term monitoring solution you can finally trust.

The only worry-free soil water potential sensor:
Ease of use isn’t something you normally associate with water potential measurement devices. Until now. That’s because TEROS 21 is plug and play in a number of ways.  First, once it’s in the ground, the durable epoxy coating ensures long-lasting usage. Second, no maintenance is involved. That means no refilling. And no worrying about frozen conditions. Lastly, the TEROS 21 water potential sensor is also easy to integrate into systems (SDI-12 compatible) so it can be used with third-party loggers. All this adds up to saving you time and a lot of unnecessary labor.

Coverage—Get the maximum for the minimum:
This is where you may expect to see a high price point for all of the extra value we engineered into TEROS 21. Instead, we offer them at a low cost so you don’t have to spend more money to get the measurement coverage you need. Not only do more sensors for the money make more sense, but because they use less energy and include a temperature sensor, you’ll also be getting more value for your money. And it’s all backed by 15 years of research.

Soil water measuring that’s immeasurable in value:
Accurate, easy to use and ffordable, the TEROS 21 water potential sensor outperforms in every aspect because we specifically designed it to save you time, hassle and money.

MEASUREMENT SPECIFICATIONS:

Water potential Range: −5 to −100,000 kPa (1.70 to 6.00 pF)
Resolution: 0.1 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 −5 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

Dielectric measurement frequency: 70 MHz

Temperature Range: −40 to +60 °C
Resolution: 0.1 °C
Accuracy: ±1 °C

COMMUNICATION SPECIFICATIONS

Output: RS-232 (TTL) with 3.6-V 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
Dimensions 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 °C
Maximum: +60 °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 SPECIFICATIONS

Supply voltage (VCC to GND):
Minimum: 3.6 VDC
Maximum: 15.0 VD C

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):
Typical: 0.03 mA

Power-up time (DDI serial):
Maximum: 50 ms

Power-up time (SDI-12):
Typical: 175 ms

Measurement duration:
Typical: 175 ms

COMPLIANCE Manufactured under ISO 9001:2015
EM ISO/IEC 17050:2010 (CE Mark)