If you can’t fix it, feature it!

That’s the motto of some rheometer manufacturers.

Good science requires accurate control of the sample gap (as a function of temperature) during rheological measurements. Confronted with changes in the sample gap that are impossible to control, some vendors are forced to add additional hardware and feedback loops to their instruments. Unable to fix the design flaws, they feature the additional hardware required for reasonable measurements.

For more than a decade TA Instruments has demonstrated the ability to deliver accurate temperature/gap compensation, over a wide range of conditions. Figure 1 illustrates the results that are obtained on a standard material, plotted against certified values. Accurate data is obtained on cone and plate geometries over a wide temperature range.

Have prospective vendors try the same experiment. Make sure the data is generated utilizing thermal gap compensation only. If any additional hardware, or calibration routines are required to generate accurate data, you’re looking at inferior technology. Politely ask the purveyor of bad science to leave your laboratory.

TA Instruments robust and precise rheometer designs eliminate the need for special geometries, and special temperature control systems. Redundant hardware, and exotic calibrations are not required to maintain an "accurate" gap on TA rheometers.