The best value in viscosity measurement and control What is the difference between kinematic and dynamic viscosity? Kinematice viscosity is the ratioof dyamic viscosity and density.  Typical units are CentiStokes [cSt].  It became a popular measurement because early viscometers consisted of a calibrated hole in the bottom of a cup.  The time it took a measured volume of fluid [cup volume] to run out the hole depended on the fluid viscosity and the density, since the more dense the fluid the greater the gravitational force on the fluid.  Absolute, or dynamic viscosity has units of centipoise or mPas.  TDC viscometers measure dynamic viscosity.  To convert kinematic viscosity to dynamic [absolute] viscosity, multiply by fluid density.  Since many fluids have a density close to unity, the two viscosity values are numerically similar. How much flow is too little and how much is too much? Although the sensor works fine without any flow, it is important to refresh the fluid in the measurement gap.  Flow also reduces the tendency for any surface film to develop.  An ideal flow would be 1-10ft/sec [0.3-2m/s].  Excess flow can gradually erode the materials used in the sensing head. What is the viscosity and temperature response time? Temperature is sensed in the middle of the sensing head, adjacent to the viscosity measurement gap.  Because of the mass of the sensor, it takes several minutes for the temperature to fully stabilize at the fluid temperature.  Viscosity and temperature are measured 5 times a second, however, since the measurements are averaged the effective response time is tens seconds when the “Fast” response is selected [serial port], and close to a minute when the “maximize accuracy” setting is chosen. What happens when the fluid is too viscous? There is no damage to the vibrating beam.  The output is full scale viscosity plus one. Does orientation of the sensor matter? No, however, avoid vertical sensor orientations on horizontal piping to eliminate gas and sediment interference. How do I operate without the display? Provide clean 24Vdc power to pin 6 while grounding pin 1.  4-20ma outputs for viscosity and temperature are available on pins 4 and 5 respectively.  If you want to communicate over the RS232 interface, pins 2, 3, and 5 are Rx, Tx, and Gnd respectively. What is the shear rate of the viscometer? The shear rate varies with time as the beam vibrates and varies with proximity to the beam, so it is not controlled as it would be in a laboratory viscometer.  On average the magnitude of the shear rate is about 5000/sec.  If you need to force the measurement to agree with a lab measurement due to differences in shear rate, there is provision for a “Field Calibration” which adjusts the measurement to a desired value.  The Newtonian fluid factory calibration can be easily restored through the serial port.