Fundamentals of quartz viscosimetry

Starting point

The principle of quartz viscosimetry is based on the idea of W.P. Mason. The basic concept is the application of a piezoelectric crystal in the shape of a torsional oscillator for the determination of viscosity. On the one hand, the high-frequent electrical field that is applied to the oscillator causes a movement of the sensor and in consequence the shearing of the fluid. On the other hand, the movement of the sensor is influenced by the external forces (the shear stress) of the fluid which affects the electrical response of the sensor.

Development of the quartz viscosimeter QVis

The calibration procedure as a prerequisite of viscosity determination using a quartz goes back to the founder and CEO of flucon fluid control GmbH B. Bode who facilitated the detailed analysis of the electrical and mechanical transmission behavior of the oscillating system. On the basis of this calibration, the quartz viscosimeter was developed which allows continuous viscosity determination in resting and flowing liquids.

The QVis is comprised of two components, the electronic unit equipped with an electronic control and evaluation system on the one hand, and the measuring head which surrounds the quartz on the other hand. The micro processor which is part of the electronic unit is responsible for determining the oscillating behaviour of the quartz crystall sensor. With the help of the calibration function, the viscosity is determined in a next step.

Advantages of viscosity measurements by means of a quartz sensor

  • no molecular destruction of the measuring fluid
  • no temperature effects on the measuring fluid
  • small sample sizes sufficient
  • large measuring range (1 to 10.000 mPas)
  • chemical resistance of the quartz sensor
  • suited for temperatures up to 500°C and pressure up to 10 kbar
  • resistant against dirt and deposits
  • easy to clean