IRROMETER — Miniature Low Tension Model MLT


Tensiometer Service Unit

Attention all Irrometer Tensiometer customers

Please note that the Tensiometer Service Unit, catalog number 1001, is necessary for all Irromter Tensiometer installations. This item is not used with the Warermark series, and is only needed for fist time Tensiometer customers. The kit includes the reservoir solution and a pump to remove air from the chamber of the tensiometer, without, the reading this device will not be accurate.

The IRROMETER Model MLT (Miniature Low Tension) was designed for use in small containers commonly used in greenhouses and nurseries. Its compact design and short insertion depth of 4.75 inches (12 cm) allows the MLT to be installed in smaller growing vessels. With a range of 0-40 centibars (cb) or kilopascals (kPa), this instrument is for use in situations where tensions above 30 cb (kPa) are rarely expected. Gauge increments of 1 cb (kPa) provide a benefit where finer resolution near saturation is needed. This model instrument is also well suited for conditions where rapidly changing soil moisture conditions need to be observed. The “Quick-Flo” ceramic tip is colored blue for easy identification.


  • Gauge with a full range of 0-40 cb (kPa)
  • “Quick-Flo” ceramic tip (blue)
  • Body-tip assembly can be easily replaced in the field
  • Compact size is designed for small containers

WARRANTY: One year


Instrument body materials: Butyrate body, ceramic tip
Reservoir section dimensions: Height 2 in. (51 mm) – 2.250 in. (57 mm) including cap
Diameter .875 in. (22 mm) – 1 in. (25 mm) including cap
Body tube section dimensions: Length: 4.750 in. (12 cm)
Diameter: .500 in. (13 mm)
Instrument weight: .17 lb. (0.077 kg)
Ceramic tip:

Blue tip – used for very coarse soils and non-soil growing media

CAP: Engineered Plastic

 1008 Standard Vacuum Gauge

Dial size 1.5 in. (38 mm)
Case Black ABS
Window Polycarbonate
Dial Scale of 0-40 cb (kPa), white with contrasting green markings
Accuracy +- 3-2-3% of span ASME B40.1 Grade B
Mechanism Bronze Bourdon Tube
Connection Standard 1/8 in. NPT - Brass Bottom Mount
Operating temperature -40° to 150° F (-40° to 65° C), 32° to 150° F (0° to 65° C) for water service


The IRROMETER operates on the tensiometer principle, which measures soil water tension. Soil water tension is the energy (vacuum) applied to the soil by the plant as it draws in water for nutrition. This force is measured in centibars (cb) or kilopascals (kPa) of tension with a high reading indicating the dry end of the scale and a low reading indicating the wet end of the scale. The IRROMETER instrument consists of a sealed, fluid filled tube that is equipped with a porous ceramic tip and a special vacuum gauge. They are installed in the soil or growing media with the tips placed at desired root zone depths. As the soil dries (increasing tension), fluid is drawn out of the instrument. This reduces the fluid volume in the IRROMETER, thus creating a partial vacuum which is registered on the gauge. The drier the soil, the higher the gauge reading. An irrigation application or rainfall event reverses this action. As water flows back into the soil (and the IRROMETER), tension is relieved in the soil and the instrument, resulting in a lower gauge reading (lower tension). In effect, the instrument is indicating how hard the roots are working. Due to the IRROMETER’s unique principle of operation, no calibrations are necessary under normal operating conditions for different soil types. A gauge reading of 15 cb (kPa) indicates that the roots are extracting the same amount of moisture whether the crop is planted in sandy soil or non-soil growing media.


The irrigation system shall incorporate soil moisture indicators to aid in making irrigation scheduling decisions. The soil moisture indicator shall operate on the tensiometer principle and indicate soil water tension, displaying in units of centibars (cb) or kilopascals (kPa). Tube shall be constructed of durable plastic that is impervious to attack by soil chemicals, with a ceramic sensing tip. It shall be designed for maximum accuracy in low tension applications. Allceramic to plastic connections shall be guaranteed leak proof. The soil moisture indicator shall be an IRROMETER Model MLT as manufactured by the IRROMETER Company, Inc. of Riverside, California.


There are no materials for downloading