Gemini HR nano - Hardware features

The Gemini HR nano offers:

• Unrivalled state-of-the-art air bearing design and performance.
• Continuous torque control range from 3nNm to 200mNm.
• nNm torque measurement accessible in all flow and dynamic control modes.
• Low inertia motor and bearing design handles large variations in crossover modulus.
• High sensitivity, low compliance and axially symmetric normal force measurement.

Rotonetic 2 Drive – unique technology

• Rotonetic 2 drive. Unique to the Bohlin Gemini and specifically optimized and enhanced for rheological testing
  
• Wide torque measurement range. Adaptive Rotonetic 2 technology provides working torque range beyond that of any conventional controlled strain rheometer
  
• Direct strain controlled oscillation. Directly driven oscillation at instructed strain amplitude without iteratively adjusting the stress cycle by cycle which accurately controls the sample’s strain history and reduces experimental time

• Step strain testing. Stress relaxation tests with a rise time of a few milliseconds and Rotonetic drive technology which perfectly maintains target strain during the stress decay whilst adaptively adjusting torque sensitivity
  
• Steady shear experiments. Rotonetic 2 drive effectively allows instantaneous changes in speed, including rapid flow reversals, whilst adaptively adjusting the torque sensitivity for measurement of even the most weakly structured samples
  

Inductive motor handles large variations in crossover modulus

Powerful yet low inertia motor design enables adjustment of position or speed more rapidly than conventional motors with permanent magnets, and optimum dynamic response necessary to perform transient and dynamic test protocols with excellent low torque response. Combining this motor technology with a high sensitivity air bearing creates a wide and continuous dynamic torque range in excess of 1:1 million, which means that large variations in crossover modulus can be properly followed.

Air bearing with torque mapping

Continuous development of proven and renowned air bearing technology has produced the most sensitive state of the art air bearing design ever fitted to a rheometer. The HR bearing achieves extremely low torque errors around 360° without compromising stiffness and strength. A continuous high resolution digital torque map allows a setting of ultra-low measurement torques, to a minimum of just 3nNm. This provides perfect low viscosity data and new measurement opportunities for probing the structure of even the most weakly structured viscoelastic dispersions.

Exceptional position and speed sensing

Proprietary hybrid position sensing technology with perfectly linear output ensures extreme position sensitivity for low strain measurements and unsurpassed dynamic range in speed measurement. Sub micro-strain position sensing complemented by the low torque response of the motor allows for extremely sensitive creep and recovery measurements. An upper speed of 600rad s^-1 can achieve shear rates in excess of 5 x 10⁵s^-1 which is applicable to coating processes for example.

High resolution normal force sensor

High sensitivity sensor acts independently of the air bearing spindle thus ensuring the normal force output is axially symmetric around 360°. Capable of measuring just 0.1g, data for the first normal stress difference can be generated even at low values of thrust. In oscillation, the sensor can be used to compress or tension a sample with a pre-defined force using Autotension mode.

Automated gap setting and control

Set from PC or instrument touch pad and can be adjusted and controlled during measurement by either temperature or normal force (Autotension).