METER Legacy Field Water Potential Sensors

METER Legacy Field Water Potential Sensors

MPS-6 (now called TEROS 21) Calibrated Water Potential Sensor

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  • Description

    The MPS-6 is a matric water potential sensor that provides long term, maintenance-free soil water potential and temperature readings at any depth without sensitivity to salts.

    The range of the MPS-6 goes from field capacity to air dry. Lab and field tests indicate that it can make accurate measurements at water potentials at least as dry as permanent wilting point.

    The MPS-6 features:

    • Dramatically improved accuracy – Accuracy (±10% of the reading) comes from the MPS-6’s six-point factory calibration. Compare with confidence to other MPS-6 sensors or to other measures of water potential.
    • Tough, long-lasting body – Epoxy overmolding will withstand even difficult field conditions. Sensors are rated for long-term research studies.
    • No recalibration – Other matrix potential sensors have a tendency to degrade over time. The MPS-6 uses a silica-based ceramic material that doesn’t degrade and doesn’t need replacement or recalibration.
    • Insensitivity to salts -The sensor is accurate in salty environments, a variety of soils, and even in locations where the salinity conditions change over time.
    • Affordability – Breakthrough calibration technique gives the MPS-6 the accuracy of an individually calibrated sensor at a price comparable to most uncalibrated sensors.
    • Excellent range – The MPS-6 has sensitivity from -9 kPa all the way to air dry (-100,000 kPa).
    • Onboard temperature measurement – Temperature measurements let you evaluate another important growing condition without adding a sensor.
    • Plug and play capability – Just install the sensor, plug it into the Em50 series logger, set the clock and measurement intervals, and start logging data. No programming required.
    • Remote access to data – Use the MPS-6 with an Em50G data logger and access your data from your office, lab, classroom, or anywhere with an internet connection.
    • SDI-12 compatible – The MPS-6 is compatible with nearly all major commercial data loggers through SDI-12, a universal communications protocol.

    How it works

    MPS-6 sensors are composed of a moisture content sensor and a porous substrate with a known moisture release curve. After the porous material has equilibrated with the surrounding soil, the moisture sensor measures the water content of the porous material, and the sensor uses the moisture release curve to translate moisture content into water potential.

    Range vs. accuracy

    A sensor’s range depends on the variation in pore sizes in the porous substrate; the wider the range of pore sizes, the bigger the measurement range. Commercially available ceramics are designed to have a uniform pore size, which limits their range. The MPS-6 uses a ceramic specifically designed with a wide pore size distribution for wider measurement range.

    However, a sensor’s accuracy depends on how well the moisture release curve characterizes the porous substrate in that particular sensor. The more consistent the substrate is from sensor to sensor, the more accurate each sensor will be. Widely varied pore sizes lead to inconsistency from sensor to sensor, putting these two critical sensor goals in conflict.

    Calibration solution

    This conflict can be resolved by individually calibrating each sensor. This has always been a time-consuming and expensive process, however.

    The MPS-6’s accuracy comes from breakthrough calibration methods that allow sensors to be individually calibrated using an automated calibration apparatus. These new techniques make the MPS-6 the first low-cost matric potential sensor with research-grade accuracy.

  • Specifications
    ACCURACYSoil Water Potential: ±(10% + 2 kPa) from -9 to -100 kPa (see manual for additional accuracy specifications past -100 kPa)

    Soil Temperature: ± 1 °C

    RESOLUTIONSoil Water Potential: 0.1 kPa

    Soil Temperature: 0.1 °C

    RANGESoil Water Potential: -9 to -100,000 kPa

    Soil Temperature: -40 °C to 60 °C*

    *Sensors can be used at higher temperatures under some conditions.  Contact METER for more details.

    MEASUREMENT SPEED150 ms (milliseconds)
    EQUILIBRATION TIME10 min to 1 hr depending on soil water potential
    SENSOR TYPEFrequency domain with calibrated ceramic discs, thermistor
    OUTPUTRS232 (TTL) with 3.6 volt levels or SDI-12 communication protocol

    *Sensors can be used at higher temperatures under some conditions.  Contact METER for more details.  Water potential measurements will not be accurate below 0 °C.

    POWER3.6 – 15 VDC, 0.03 mA quiescent, 10 mA max during 150 ms measurement
    CABLE LENGTHSensors come standard with 5 m cable. Custom cable lengths available. Maximum cable length of 75 m. Please contact METER if you need longer cable lengths.
    CABLE CONNECTOR TYPES3.5 mm “stereo” plug or stripped and tinned lead wires (3)
    SENSOR DIMENSIONS9.6 cm (l) x 3.5 cm (w) x 1.5 cm (d)
    DATA LOGGER COMPATIBILITY (NOT EXCLUSIVE)METER ZL6, Em50/50G (rev 2.13+), EM60/60G, ProCheck (rev 1.53+), Campbell Scientific, any SDI-12-capable data logger
    WARRANTYOne year, parts and labor
  • Comparisons
    ACCURACY± 10% of reading + 2 kPa from -9 to -100 kPa± 25% of reading + 2 kPa from -9 to -100 kPa±0.5 kPa±0.5 kPa±0.5 kPa±0.5 kPa
    RANGE-9 to -100,000 kPa-9 to -100,000 kPa+100 kPa to -85 kPa (-200 kPa*)+100 kPa to -85 kPa+100 kPa to -85 kPa+100 kPa to -85 kPa
    POWER REQUIREMENTS3.6-15 V, 10 mA3.6-15 V, 10 mA5-15 VDC5-15 VDC3.6 V-15 VDC5-15 VDC
    MEASUREMENT OUTPUTDigital SDI-12Digital SDI-12AnalogAnalogDigital SDI-12, RS-485Digital SDI-12, RS-485
    METHOD USED FOR DETERMINING WATER POTENTIALCapacitance of a ceramic matrix, 6 point calibrationCapacitance of a ceramic matrix, 2 point calibrationPiezoelectric pressure sensor, Wheatstone full bridge
    BEST FOR– Long term research studies

    – Natural environment monitoring

    – Low cost irrigation monitoring– Column & Spot Measurements in the Laboratory

    – Small point measurements

    – Long term field studies

    – Vadose zone hydrology

    – Long term field studies

    – Vadose zone hydrology

    – Long term field studies

    – Vadose zone hydrology

    – Monitoring in remote sites

  • Manuals and software

TS1 Smart Tensiometer (discontinued)

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  • Description

    Eliminates routine maintenance

    If your task is soil water monitoring you know the problem: water vaporizes and is lost. If soil gets dryer than about 85 kPa, no tensiometer is able to take measurements. Still, as only little water movement occurs in extreme dry soils, losing readings is tolerable. Then, when the soil gets wet again, the tensiometer could actually restart measurements – but first it needs to be refilled again.

    Automatic refilling, de-aeration

    The TS1 solves this problem. When the cup needs to be refilled and soil water is available, the internal pump will draw water from the soil, refill the cup and remove all air through an exhaust outlet – all automatically. The cup is de-aerated automatically, even if only a bubble is detected.

    Automatic emptying

    If the temperature probe indicates emerging frost, the TS1 empties itself to prevent damages caused by freezing.

    Typical applications

    • Ecological impact studies
    • Agricultural studies
    • Model calibration
    • Long time monitoring studies
    • Water balance and transport studies


    • Field measurements of pF/wc
    • Automatic self-refilling and deaerating
    • Continuous fill level controlling
    • Automatic emptying before frost
    • Integrated soil temperature probe
    • Integrated data logging function
    • Low maintenance
    • tensioLINK RS-485 interface
    • SDI12 interface


    • Not for permanent dry soils
  • Specifications
    CERAMIC CUPHigh-strength special ceramic with homogeneous porosity

    Length: 60 mm

    Diameter: 40 mm

    TEMPERATURE SHAFTVarious lengths available (standard 200 mm)

    Diameter: 40 mm

    Material: acrylic glass

    **Please indicate shaft length on your order!**

    ACCURACYSoil water tension: ± 0.5 kPa

    Temperature: ± 0.1 °C

    OUTPUT SIGNAL ANALOGSelectable Ranges: 2 x 0 … 1 V / 2 V / 5 V
    DELIVERY CONTENTSQuartz clay powder, shaft water protection cover, calibration certificate, user manual
    DATALOGGER COMPATIBILITYCampbell Scientific, Infield 7
    CABLE1.5 m; 8-pin plug M12; pigtail adapter available for connection with CSI dataloggers
    METER uses UV-resistant, durable materials for long-term field studies. Seals and screw connectors are watertight according to IP 68.
  • Manuals and software

Tensiometer Accessories

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  • Auger Kits for Pore Water Samplers and Tensiometer

    The cutting edge of the auger has a tapered tip similar to the shape of a tensiometer or pore water sampler.  Thus, the bore hole is large enough to insert the shaft, but the cup will have a tight and perfect fit to the soil.

    The unadvisable slurrying of the cup with quartz clay can be avoided.

    A divisible auger set includes:

    • cutting edge with tapered tip
    • handle with hammering head

    Parts have threaded connection and can be extended with one or more 100 cm extension rods.


    • Simplifies installation of shafts
    • Avoids slurrying
    • Multipart – divisible – extendable
    • Cutting edge
    22 mm dia. x 50 cm26 mm dia. x 50 cm
    • Tip
    20 mm dia. x 5.6 cm24 mm dia. x 5.6 cm
    • Total length
    1.25 m1.5 m
    • For shafts with
    20 mm dia.24 mm dia.
    Part no.TB-20/125TB-25/150
    Extension rod Part no.TBE-100
  • Infield 7

    The INFIELD7 is a multi-functional handheld read-out unit for all UMS tensiometers. Download readings to PC with accessory USB converter.


    • Memory for 250 readings
    • Vertical water column compensation for tensiometers
    • T8 and TS1 configuration
    • Carrying case
    • 4 AA batteries

    Looking for a data logger for long-term installations? Contact METER support.

  • Lab Refill kit for tensiometers

    Lab refill kit for tensiometers (includes T4 and T8), includes stand with clamps, adapter that fits sensor body, 500 mL bottle, pressure gauge, tubes, beaker, and refilling syringe.

  • Refill kit for external refillable tensiometers

    Refill kit for external refillable tensiometers (includes T4e and T8), includes hand-operated vacuum pump, 500 mL bottle, refill syringe, tubes and valves.

  • tensioLINK USB converter

    The tensioLINK USB converter is used for directly connecting sensors and devices with serial tensioLINK to a PC.  One can configure features and read out measured data.

    UMS devices with 8pin M12 connectors (e.g. TS1 or T8 tensiometers) could be directly connected to the converter without the need for a further power supply.  The sensor is powered through the USB interface.

    Use with the PC-Software tensioVIEW.  Manual software and driver come along with supplied CD.

    Sensor Supply9 VDC / 100 mA tolerance +1 V
    Short Circuit2 Min.
    Galvanic Isolation1 kV
    Serial Sensor InterfaceRS485-2 wire, ESD protection 15 kV
    USB interfacecompliant to USB 1.1 and 2.0

It’s not immortal, but almost

Specifically designed for field-use, the T4 tensiometer ceramic and shaft are engineered to be virtually indestructible when it comes to harsh weather.

Simply accurate. Simply fast. Simple to use.

With the WP4C, soil moisture release curves in the dry range have never been easier.