Established in 1850, Poulten Selfe & Lee (PSL), is a manufacturer of high quality glass capillary viscometers as well as the "PSL-RHEOTEK" range of automatic viscometer systems.

PSL provides direct measurement traceability from an in-house master viscometer scale maintained in accordance with international standards. The PSL Calibration Laboratory is accredited by the United Kingdom Accreditation Service and offers a range of ISO 17025 viscometer calibration services, as well as viscosity reference materials.

RHEOTEK is a trademark of Poulten Selfe & Lee Ltd. The PSL-RHEOTEK range of instruments include viscometer baths and automatic viscometers suitable for the precision measurement of petroleum liquids, polymers, pulp and inks.