Rotational Viscometer / infinite-gap geometry
Rotational viscometers are the widest spread viscometers on the market and can be found in more or less all industries independent of company size. The easy filling of a simple sample container and the fast and easy exchange of the measuring bob make rotary viscometers the most versatile instruments, giving good results in various applications. Rotational viscometers are typically used for quality control.
Results provide reasonable repeatabilty but the absolute precision is not reliable due to inadequate temperature precision. The listed specifications apply to a typical instrument with spring mechanics and a classic cylinder or disc spindle in a large sample vessel. The resulting wide gap between the bob and the vessel's wall is assumed to be infinite. The viscosity calculation is based on this assumption.
Physics
- Measured quantity: Torque
- Calculated quantity: Dynamic viscosity
Learn more about the Rotational Principle.
Performance
Rotational viscometers cover a very wide measuring range. For systems that use a spring for measuring the torque, there are different models designed for different viscosity ranges. The higher the tested viscosity is, the stronger the spring has to be. Each viscometer model comes with a number of different measuring spindles. One spindle is suitable only for a part of the model's measuring range.
- Viscosity measuring range - for a model for medium viscosity materials, with several different spindles: 100 mPa.s to 4,000,000 mPa.s
- Accuracy: approx. 20 %
- Temperature measuring range: typically ambient
In addition, there are special sample adapters available for reducing the required sample volume, for extending the measuring range and for a wider temperature range.
Temperature control
Rotational viscometers that test typically 500 mL of sample in an open beaker are in most cases operated without temperature control. Tests are performed at ambient temperature. Still, thermostat baths are available that can hold even a 500 mL beaker.
Sample
- Typical sample volume for manual operation: 500 mL
- Suitable for transparent and opaque samples.
Standards and Norms
A great number of standards is available for rotational viscometers, among them for example:
ASTM D2196, ASTM D2393, ASTM D2556, ASTM D2669, ASTM D2983, ASTM D3232, ASTM D5133, USP <912>
Overview
| Viscometer type | Rotational Viscometer / open beaker |
|---|---|
| Measuring principle | Rotational Viscometer |
| infinite-gap geometry / open beaker | |
| model for medium viscosity materials (R) | |
| Measured quantity | torque |
| Calculated quantity | dynamic viscosity |
| Viscosity range - min | 100 mPa.s |
| Viscosity range - max | 4,000,000 mPa.s |
| Temperature - min | typically ambient |
| Temperature - max | typically ambient |
| Liquid bath thermostat required | no |
| Temperature change with same filling | limited |
| Automation possible | no |
| Sample volume - typical | 500 mL |
| Solvent volume - typical | --- |
| Sample throughput - max / h | --- |
| Measuring accuracy | approx. 20 % |
| Shear rate control | no |
| Shear rate calculation | no |
| Lab space | < 0.25 m² |
| Standards and norms | e.g. D 2196, D 2393, D 2556, D 2669, D 2983, D 3232, D 5133, USP <912> |
We offer typical values which are based on the values in brochures and standards but are not related to specific instruments.