Select the spindle
The process of selecting a spindle and speed for use with a Brookfield viscometer is ultimately trial and error. However, there are a few ways to narrow down the possibilities before doing any testing. If a sample was historically tested with a particular speed and spindle combination, the user should use that same combination. This helps ensure that test results are accurate and repeatable. The goal is to choose a spindle with a dial or digital display that produces 10% to 100% torque.
When the viscosity of the fluid is known
The maximum viscosity range for a spindle running at a given speed is equal to the spindle factor multiplied by 100. This is the full scale range for that spindle/speed combination. The minimum measurable viscosity is equal to 10 times the coefficient, or one tenth of the full scale range. Knowing the full scale range allows you to determine if your fluid is capable of that spindle/speed combination.
In addition, digital viscometers equipped with the AUTO RANGE key can automatically obtain the full scale range. Enter the spindle code and RPM setting, then press the AUTO RANGE key. The viscometer will calculate and display the full scale viscosity for that spindle and speed combination.
When the viscosity of the fluid is unknown
If the reading is below 10% or above 100%, the user should select a different speed to obtain a reading within the recommended range. If changing the speed does not provide a reading between 10% and 100%, the user should try another spindle. In general, if the reading is above 100% at the lowest speed, the next smallest spindle should be used. If the reading is below 10% at top speed, the next largest spindle should be used.
To test fluids at multiple speeds, choose a spindle that will produce a 10% to 100% reading for at least three speed settings.
