Viscosity Process Analyzers
In the Viscosity Process Analyzers , a capillary type of viscosimeter with external pressure, the pressure drop resulting from a constant flow of a fluid through a capillary of constant dimension is measured as dynamic viscosity. The measurement is not absolute, i.e. the viscosity process analyzer has to be calibrated with two fluids of known viscosities. For a fluid of constant density the reading of the measured variable may also be interpreted as kinematic viscosity. Varying densities, however, would require measurement of the density for correction.
The measuring principle is based on the Hagen-Poiseuille Equation. Continuous volume flow is forced and simultaneously measured by a pneumatically-driven metering cylinder ; piston speed is adjusted so that the differential pressure transmitter is always observed at a pre-selected point of its range . The entire analyzing procedure is microprocessor-controlled; this includes an automatic and continuous kinetic energy adjustment known as the Hagenbach Correction ; this also includes compensation for varying the piston speeds. C Temperature control of the oil filled bath is maintained within + 0,05° . Constant sample input temperature should be maintained. The inlet or outlet valves prior to the cylinder are routinely checked for tight closure . The analyzer cycle time depends on sample parameters .Repeatability and reproducibility are equal or better than the limits indicated in corresponding standards and norms.