What you can measure

  • Oil-water interfacial tension 
    Measured with a Du Noüy ring in accordance to the ASTM D971 and IEC 62961 standards
  • Surface tension
    Du Noüy ring method
  • Interfacial tension
    Du Noüy ring method
  • Critical Micelle Concentration
    Manual measurements with Du Noüy ring
  • Density
    Density probe

A quick view

In this 2-minute video, you can explore just how easily Sigma 702ET guides you through interfacial tension measurements of transformer oil. 

3 reasons to invest

Guiding nature

This instrument is designed to simplify the work for you. It guides you through the measurement process of interfacial tension of transformer oil and water according to relevant standards. 

High-end accuracy

Precision in both microbalance and mechanics give you excellent accuracy for you measurements. 

Results on the go

With the standalone functionality there is no need for an external computer. Your results are displayed on a large integrated screen and can easily be printed or exported to your PC. 

Learn more

Quality Control of Transformer Oil

Testing interfacial tension of oil and water with the ring method.

The IEC 62961 and ASTM D971 standards are used to determine the possible contaminants of hydrocarbon fluids. The purity of hydrocarbon fluids is important in many industrial areas, such as in aviation, diesel fuels and transformer oils.

It is well known that oil-water interfacial tension correlates with the purity and functionality of oils that are used in transformers for cooling, insulation and protection against arcing. Electrical stress and contamination may modify the oil performance.

Sigma 702ET with a platinum Du Noüy ring is an excellent choice for controlling the oil quality according to IEC 62961 and ASTM D971-12 standards.

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A closer look

Dive into the specifics of Sigma 702ET and compare it to our other instruments to make a smart decision on what you need. 

Sigma 700
Sigma 701
Sigma 702
Sigma 702 ET
Sigma 703 D

Available Measurements 

Surface tension

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Interfacial tension

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Critical Micelle Concentration

 Automatic  Automatic  Manual  Manual  Manual

Dynamic contact angle

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Surface free energy

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Powder wettability

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Balance Specifications 

Measuring range (mN/m)

1…2000 1…2000 1…1000 1…1000 1…1000

Displayed resolution (mN/m)

0.001 0.001 0.01 0.01 0.01

Density range (g/cm3)

0…2.2 0…2.2 0…2.2 0…2.2 0…2.2

Density resolution (g/cm3)

0.0001 0.0001 0.0001 0.0001 0.0001

Maximum load (g)

210 5 5 5 5

Weighing resolution (mg)

0.01 0.005 0.01 0.01 0.01

Force resolution (µN)

0.1 0.05 0.1 0.1 0.1

Contact angle range (°)

0…180 0…180        –        –        –

Contact angle resolution (°)

0.01 0.01        –        –        –

Calibration & Locking

Automatic Manual Manual Manual Manual

Measuring Unit Specifications    

Sample stage

Motorized Motorized Motorized Motorized Manual

Sample stage speed (mm/min)

0.01…500 0.01…500 0.01…500 0.01…500        –

Stage positioning resolution (µm)

0.016 0.016 0.26 0.26        –

Dimensions (L×W×H, cm)

33.3×24.4×62 33.3×24.4×62 33.3×24.4×62 33.3×24.4×62 27.5×15.5×39.

Weight (kg)

16.3 13 10.7 10.7 4.9

Power supply (VAC)

85…264 85…264 85…264 85…264 100…240

Power consumption (W)

13 13 13 13 7

Frequency (Hz)

47…440 47…440 47…440 47…440 50…60

Common Accessories

Temperature control range (° C)

-20…+200 -20…+200 -20…+200 -20…+200 -20…+200


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Provided software

OneAttension OneAttension Data receiver Data receiver Data receiver

System Requirements 

Recommended system requirements

  • 1 GHz processor
  • 1 GB RAM
  • 40 GB hard disk drive (20 GB free)
  • 1 USB-port
  • Accessories such as water bath and liquid dispenser may require a free USB port

Operating system requirements

  • Windows 7 & 8 &10 (32 or 64 bit)
  • Windows Vista (32 bit)

Embedded Software and Data Receiver

Sigma 702ET comes with a powerful embedded software that guides the user in the measurements according to the relevant standards and shows the results on the integrated screen. Data can be also stored in PC with Data Receiver software for additional data storage and reporting.

Software Features

  • Standalone
    Run the measurements and read the results onscreen
  • Intuitive and easy to run
    The software guides you in the measurement process according to ASTM D971 and IEC 62961 standards
  • Versatile data storage
    Read the results onscreen, send them to PC or print them out with an optional printer
  • Automated
    Set the parameters and press start, everything else will be done for you

Add more possibilities

Simplify your work and explore more with these selected extras for Sigma 702ET. You can find the full range below. 



Platinum Du Nouy ring

Pt-Ir-ring made to fulfill the requirements at least in following standards; ISO 301, ISO 4311, ISO 6889, ASTM D1331 and ASTM D 971. Includes also additional weight for push-mode.


Thermostatic vessel

Chamber made from Teflon and Aluminum for temperature control of the sample liquid. A heat exchange vessel with fluid jacket type of construction. Heating/cooling of the fluid jacket requires external bath/circulator (T102ME or T102USB). Fits glass sample vessel 70 mm in diameter (T104). Operable temperature range from -20 to +200°C .


RS232-compatible printer

For printing results directly from instrument into paper.

What others say

Our instruments are present at many prestigious universities and research facilities world wide. Take a minute to find out what others say about our Sigma Instruments. 



Researcher at Riken, Japan


Riken, Japan

Riken is a Japanese research institute established in 1917. Its research areas include physics, chemistry, biology, medical science, engineering and computational science.

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