TEROS 31 Tensiometer

Tiny tensiometer tackles big problems

If you need spot measurements of water potential in soil columns, soil cores, or sampling rings, there aren't a lot of options. Until now. With the TEROS 31, we put our 25 years of expertise to work in the smallest space possible: a ceramic tip with a surface area of only 0.5 cm2. It's the only tensiometer in the world small enough and precise enough to perform excellent water potential spot measurements in even the tightest spaces. And now it's even better.

Double your data power

The TEROS 31 combines METER world-renowned precision technology with the power of ZENTRA Cloud, giving you easier, faster water potential data in near-real time. And compatibility with the ZL6 data logger means precision is now plug-and-play, making setup a breeze. The TEROS 31 minor footprint allows major advantages over larger tensiometers, such as very little soil disturbance and incredibly fast response time. And, because of its small size, it's one of the only tensiometers in the world that can extend its measuring range.

Lab tensiometer with heroic strength and speed

TEROS 31 is more robust than ever before. Technological advancements have made it possible to incorporate a more ruggedized, highly precise pressure transducer, giving you higher data resolution in an almost unbreakable form. And the TEROS 31 tensiometer has a superheroic response time of only 5 seconds for a pressure change of 0 to -85 kPa. It reacts much faster to changing soil conditions because of its small water volume, enabling you to measure even the most minute changes in water potential-something lower-quality tensiometers cannot do. It measures matric potential within the gravitational range where most water movement occurs and into the capillary range, helping you understand whether water will move and where it will go.

Tensiometer measurement range-extended

Most tensiometers have a measuring range of at least 100 to -85 kPa. But the TEROS 31 increases the matric potential measuring range to nearly -150 kPa. How is this possible? Normally, when a tensiometer reaches -85 kPa, the water boils, forming an air bubble. The air bubble expands and contracts with changes in pressure, making the tensiometer unable to measure suction. But the TEROS 31 retards the boiling point, extending the measurement range well beyond normal limits.

Setup in seconds

Now you can spend far less time on complex setup. Just insert the TEROS 31 stereo plug into the ZL6 data logger, and start seeing numbers. ZENTRA Cloud makes it possible to see near-real-time data wherever you are. TEROS 31 can be installed in any position and orientation and comes with a miniature auger to ensure as little soil disturbance as possible.  For spot measurements, just auger a 5-mm hole and insert the tensiometer. It's that simple. To save you even more time and effort, bubbles are detectable through the transparent shaft, making it easy to see when it's time to refill.

Small tensiometer-huge benefits

For more than a quarter of a century, METER has been the leading expert in the development of tensiometers with over 10,000 sold. Nobody in the world makes an instrument this small, this simple, or this precise. Trust the TEROS 31 lab tensiometer for fast, accurate spot measurements in all your tightest spaces.

Feature Specification
Water potential Range: -85 to +50 kPa (up to -150 kPa during boiling retardation)
Resolution: ±0.0012 kPa
Accuracy: ±0.15 kPa
Temperature Range: -30 to +60 °C
Resolution: ±0.01 °C
Accuracy: ±0.5 °C

NOTE: If the sensor unit is not buried, measured temperature may diverge from soil temperature.
Output DDI serial
SDI-12 communication protocol
TensioLINK communication protocol
ModbusTM RTU communication protocol
Data logger compatibility METER ZL6, EM60, and Em50 data loggers or any data acquisition system capable of 3.6-28.0 VDC excitation and SDI-12, ModbusTM RTU, or tensioLink communication.
Dimensions Width: 23.5 cm (0.93 in)
Depth: 17.5 cm (0.69 in)
Height: 49.0 cm (1.93 in) Max. overpressure ± 300 kPa
Tensiometer shaft diameter 5 cm (0.19 in)
Tensiometer shaft length 2, 5, 7, 10, 15, or 20 cm
Operating temperature range Minimum: 0 °C
Maximum: 50 °C
COMPLIANCE Manufactured under ISO 9001:2015
EM ISO/IEC 17050:2010 (CE Mark)

We periodically send an email newsletter containing updates, new product releases, training and advice. If you would like to receive these please subscribe below.


Labcell Limited exclusively supply and support METER products in the UK & Ireland.

Non UK/Ireland Customers, please contact METER Environment at:www.metergroup.com/environment/

TEROS 31 small


  • Laboratory tensiometer
  • Easy data visualization in real time: plug and play with ZL6 logger and ZENTRA Cloud
  • Small and fast
  • Little soil disturbance
  • Extended range
  • Install tensiometer in any position or orientation
  • Bubbles easily detectable through the transparent shaft
  • Output signals are balanced
  • Accurate zero-tension reading

Learn more with articles, case studies, demos and webinars;

TEROS 31 Manual
Size: 1.8 MB (1,860,145 bytes)

TEROS 31 Quick-start Guide
Size: 1.4 MB (1,472,205 bytes)

TEROS 31 Integrators Guide
Size: 600.2 KB (614,555 bytes)

Quotation Request

Email us to request a quotation for the TEROS 31 Tensiometer