How our Viscometer Works

The Power of a Simple Solution 

Cambridge Viscosity's viscometers are highly accurate, reliable and self-cleaning by design.  The company's patented technology uses only one moving part, a piston, driven electromagnetically through fluid in a small measurement chamber.  Proprietary circuitry then analyzes the piston's travel time to measure absolute viscosity and monitor temperature.  With all wetted parts Stainless Steel, and state-of-the-art microprocessors, the Cambridge viscometer is nearly maintenance free and extremely inexpensive to install.  Constant motion of the piston keeps samples fresh, while mechanically scrubbing the sampling area.

In-line Application with Viscometer Mounted in Flow 

For laboratory units less than 2 ml is placed directly into the measurement chamber.

This image is animated to show operating principle.

The patented Cambridge electromagnetic viscometer design is very simple.  In a process application, the viscometer is inserted into a flowing liquid as shown above.  Inside the measurement chamber is flooded constantly with new fluid sample.  A hollow, neutrally-buoyant magnetic piston is retained by a removable fence that also deflects fresh fluid samples into the chamber.  Two coils are imbedded in the tip of the viscometer surrounding the measurement chamber.

When the inner "B" coil is activated the magnetic force on the piston pulls it down toward the base of the chamber.  Access fluid trapped behind the piston is forced to flow around the piston.  The more viscous the fluid the slower the piston motion.  The upper "A" coil is used to magnetically monitor the motion.

As soon as the piston reaches the bottom of the chamber, the upper "A" coil is activated and the lower coil is used to monitor the piston motion.  During this reverse cycle, fresh fluid is pulled in behind the piston and the inner "B" coil is used to monitor the motion.  As soon as the piston approaches the deflector fence, coil "B" is again activated and the process repeated.  The total two-way travel time is a very accurate measure of the fluid's absolute viscosity (centiPoise) to within a +/-1% specification.

As the piston is driven back and forth, both the retaining fence and the piston motion continuously refresh the fluid samples.  Since the piston is low mass, the sensor is insensitive to vibration or changes in orientation.  The two-way measurement cycle takes, on average, about five to ten seconds, so data is frequently updated.  Throughout the cycle fluid temperature is measured using a platinum RTD mounted at the base of the chamber.