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I would like to measure viscosity, but do not have access to a viscometer. If possible, I would like to avoid having to purchase one. I have access to many other flow measuring devices, including flowmeters, pressure sensors, and a turbidimeter, and was wondering if taking measurements with these would somehow allow me to make, at the very least a proportional measurement to viscosity (I only need relative measurements between different fluids, exact specifications are not necessary). I dont have reason to believe these liquids would behave significantly non-newtonian, and they would likely all be water with additives such as salt and detergents.

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A long glass tube and a steel ball which matches the internal diameter closely - then measure the different times compared to some known liquids for the ball to drop a given distance.

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  • $\begingroup$ Actually it is easier to get consistent results when the tube is much larger diameter than the ball. If the ball is a close fit, the fluid has to move up through the narrow gap between the ball and the tube, faster than the ball is descending. This can cause turbulence and instability ("the ball "wobbles" as if falls) and correcting for those effects is hard! $\endgroup$
    – alephzero
    May 23, 2019 at 20:19
  • $\begingroup$ @alephzero but if the clearance is too great then for somewhat similar liquids there may be very little time difference... $\endgroup$
    – Solar Mike
    May 23, 2019 at 20:23
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punch a small hole in the bottom of a plastic container. measure the time it takes for the container to empty through the hole. experiment with different hole diameters to "scale" the effect appropriately for your expected viscosity values, and calibrate it against a standard.

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  • $\begingroup$ For small holes, the different surface tension of different liquids may cause significant errors. $\endgroup$
    – alephzero
    May 23, 2019 at 20:15
  • $\begingroup$ this technique is used in the petroleum industry, where the liquids involved have about the same surface tension. $\endgroup$ May 23, 2019 at 21:14
  • $\begingroup$ And in spray painting, where the important feature is to get repeatable viscosity when you're spraying. $\endgroup$
    – TimWescott
    May 23, 2019 at 23:45

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