Dry lab corn syrup viscosity
Sadly, we did not do much with cone-and-plate viscosity this year. You can read about it in the HowTo
guide for our lovely, reliable Wells-Brookfield viscometer (http://macro.lsu.edu/howto/WELBROOK.DOC).
The device is simplicity itself: a shallow metal cone rotates at a steady speed (given in rotations per
minute, or RPM) above a flat metal plate. A fluid situated in the gap provides viscous drag. The torque
required to rotate the cone at a certain rate is measured and displayed as a digital signal from 0 to 100. To
convert this to viscosity, one multiplies by what the instrument manual calls the RANGE parameter. Here
are some results on corn syrup:
RPM
6
3
1.5
0.6
0.3
1.
2.
3.
4.
5.
6.
7.
ShearRate Range
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
45
51.4
59.4
59.1
64.6
64.5
61.9
22.5
102.8
36.2
36
31.6
31.8
33.9
11.25
205.6
19.8
19.7
15.2
14.7
14.75
4.5
514
8.3
6.9
9.5
4.9
7.4
2.25
1028
4.3
3.6
3.5
3.4
3.7
You are to determine the apparent viscosity by multiplying the average of the five trials into the range
parameter.
Also compute the standard deviation (function STDEV in Excel is one way to do this).
Plot the apparent viscosity (and error bars) against shear rate.
What is the zero-shear-rate viscosity and its uncertainty?
Repeat the exercise after adding an offset of 3 units to your average (this simulates a malfunction in
the instrument—e.g., offset error).
Does the fluid seem to be Newtonian?
Would you have reached the same conclusion if you did not know about the offset error?
So….the
is very s
accounte
can be d
when the
You wou
non-New
An Origi
If you go
add 3 un
that the
This enh
non-New
offset er