Anton Paar Introduces the MCR 702 Rheometer with Modular TwinDrive Technology

Anton Paar introduces a rheometry revolution: The MCR 702 with modular TwinDrive™ technology. This is the only available rheometer to cover all possible rheological applications – with an accuracy of 1 nNm and features like the IsoLign Piezo flange, offering measuring gap control down to an unprecedented size of 10 nm.

Anton Paar’s TwinDrive™ technology combines two powerful synchronous EC (Electrically Commutated) motor units in a modular setup: The upper EC motor in the rheometer is permanent, while the lower EC motor can be extracted and integrated at will. Due to the EC motors' renowned dynamism and precision, users have several options of how to employ these units to fit their specific requirements.

MCR 702, the world’s first TwinDrive™ rheometer, can be operated in several test modes to cover all rheological applications – past, present and future.

2EC mode
Operating two EC motors at once opens up entirely new possibilities like counter-rotation, for example. In this “2EC counter-rotating” mode, MCR 702 employs both EC motors as drive units as well as torque transducers. The motors are easily set to rotate in opposite directions; the preset speed is divided and shared by the two motors.

This mode is an invaluable option for microscopy applications, in which the observation of sample particles and structures is sometimes difficult if the sample is sheared and therefore “rushing past” the microscope. The EC motors’ counter-rotation can be used to produce a permanent stagnation plane in the measured sample, which is therefore easier to investigate microscopically. Users can easily move the level of this stagnation plane by adjusting the two motors' individual deflections – a simple balance act for the system, yet an unprecedented rheological procedure.

Regarding speed, the 2EC counter-rotating mode simply “doubles the score”. Since the maximum speed difference of the two motors is twice as high as the speed of a single EC motor, the maximum speed difference is doubled – up to 6000 rpm. To determine the required rheological parameters, the speed is calculated from the difference between the two motors’ individual speeds, while the torque of one of the motors is recorded.

The 2EC mode also enables users to employ the motors in a more synchronized fashion, making “different demands” on each of them. Because of the EC motors’ outstanding precision, one motor is easily brought to a standstill and operated solely as a torque transducer, while the other motor is used as a drive unit only. This turns MCR 702 TwinDrive™ into the best available separate motor transducer rheometer for rotational and oscillatory tests, at the unrivaled torques and normal forces offered by Anton Paar’s EC motors only.

The list of potential TwinDrive™ applications is endless – rheologists can now begin to imagine future possibilities.

EC mode
In the EC mode, MCR 702 offers users the TruStrain™ capability of the EC motor as well as the option of performing “classic” stress-controlled tests.

In this mode, the lower motor is removed and the upper EC motor is used as a single drive unit and torque transducer. Based on the modular concept of Anton Paar’s MCR series, the removal of the lower motor is easy and reliable, supported by ToolmasterTM, the MCR's automatic tool recognition and configuration system.

The EC motor measures and controls the required parameters at the same time. Employing a single drive only, users are given the option of either controlling the shear rate or the shear stress, which opens up the wide array of applications only available for single-motor MCR rheometers.

When operating MCR 702 in the EC mode, users can attach more than 35 different temperature devices or application-specific accessories, all of them readily recognized and configured by Toolmaster™. Whether users choose to employ a cell for high-pressure applications, a device for rheological investigations while applying a magnetic field, or a small-angle light scattering system – the required devices are simply attached. For temperature control in the EC mode, a wide range of MCR temperature devices are available, such as C-PTD 200 and C-ETD 300 for concentric-cylinder measuring systems, or temperature devices for cone-plate systems with full TruGap™ functionality.

IsoLign: Complete gap control
MCR 702 TwinDrive™ is the first rheometer to offer nano-scale precision on several counts – such as low-torque measurements down to a minimum of 1 nNm and the control of angular deflections down to 100 nrad. Now this peak precision also extends to the system’s measuring gap control: The new IsoLign Piezo flange performs gap size changes as small as 10 nm. Based on a system of 3 Piezo elements in the flange of the measuring chamber reception, IsoLign is reliably employed in all TwinDrive™ test modes.

Common step-motor-based systems employ a long kinematic chain to translate single motor steps into gap size changes in the micrometer range. Capable of step sizes down to 10 nanometers, IsoLign is decades more precise than any other comparable solution for gap size adjustments.

In high-sensitivity tests over long periods of time (e.g. creep, step strain or step shear rate tests on complex fluids) and tests across vast temperature ranges, the measuring gap is kept constant within lower tolerances than ever before. In combination with the TruGap™ system (US Patent 6,499,336), stable gap conditions are guaranteed over extended measuring times as long as several days.

The key to accuracy: The EC motor technology
The air-bearing-supported synchronous EC (Electrically Commutated) motor is the key component of the MCR series’ dynamism and precision.

Whether users perform zero-shear viscosity determinations of low-viscosity polymers or measure highly viscous magnetorheological fluids at high shear rates and strains, the EC motor ensures accuracy across a vast viscosity range. Due to its unique design, the motor features a linear relation between the torque and the input current to the stator coil, which is a great advantage for precise torque control and measurement.

For increased testing flexibility, the motor is easily and reliably set to move in two respective directions depending on the selected test type, allowing for counter-rotation in the 2EC mode, for example.

Based on its rapid and accurate control combined with its extremely wide torque range, the motor is the ultimate torque transducer in the 2EC separate motor transducer application.

The established air bearing technology - with a radial and axial air bearing supporting the motor - is independent of external influences and therefore applicable without further electronic control. Continuously optimized for rigidity, drift stability and robustness, this technology enables low-torque measurements down to a minimum of 1 nNm.

The high sensitivity and increased sampling rate of the patented normal force sensor (US Patent 6,167,752) integrated in the air bearing enables normal force measurements during transient and steady-state tests as well as static normal force measurements for DMTA, tack or penetration tests. The advantage of the sensor’s location: Normal force measurements are available for all temperature devices and application-specific accessories.

In summary, MCR 702 TwinDrive™ is a high-precision gateway into the entire world of rheological possibilities.