Trying to make sense of the standard stormer viscometer and methods that could be used to calibrate a device, I’ve been looking at the original stormer viscometer in order to get an idea of what ‘grams’ actually means in the case of the stormer viscometer. Here are some facts.
The weight in grams is held on a pulley and pulls on a rotating pulley that is 1.125″ in diameter. That pulley rotates some gears or belts at a ratio of 11:1 (1 rotation of the pulley = 11 rotations of the spindle). Taking the torque applied on the main pulley and dividing it by 11 results in the actual torque to the spindle.
Simply because I use it in these cases, here is the conversion ratio for grams hung on the instrument to oz-inches. Also, one should keep in mind that there is some loss of torque due to mechanical limitations.
oz-inches == .00367056 * grams
therefore, using this formula, a KU meter ranging from 32 grams to 1099 grams ranges from .1174 oz-in to 4.0339 oz-in.
yay! Hopefully someone finds this useful as well. 🙂
After many a day scratching my head as to why I can’t get my viscometer to calibrate correctly, even assuming logarithmic and quadratic relationships, I find out why I have been having so many problems.
Krebs units are in not very linear!
I have found an old chart with lots of grams to krebs conversions on it and after painstakingly transcribing them, I have come up with the following graph.
As you can see, there are a number of points of inflection along this graph. Here are some images of the various best fit scenarios regarding this set of points. These points encompass the KU values 40.1 to 141, just for reference.
As you can see, a quartic relationship is quite passable though I still added a quintic relationship. It may be possible to make a simpler equation based on these values but I thought it prudent to stick to what I know.