fann 35A - Spring Constant Calculation Method

Model 35 Viscometer Instruction Manual
208878 Revision N, February 2013 30
7.3 Spring Constant Calculation
This calculation applies to the dead weight calibration method.
θ
grG
K
s
××
=
Equation 7-4
where
K
s
is the spring constant in dyne-cm/degree deflection
G is the load in grams
g is the gravitational constant at 981cm/sec
2
r is the radius arm at 1cm
θ is the dial reading in degrees
Example: The required setting for the F1 spring is 386 dynes/cm/degree
deflection with the R1-B1 combination. Using the 50 gram weight supplied with
the calibration kit, the spring constant is
°=
××
= 127
386
981150
K
s
Table 7-3 Torsion Spring Specifications
Torsion
Spring
Assembly
Torsion Spring
Constant*
k
1
(dyne/cm/degree
deflection)
Torsion
Spring Factor
f
Maximum Shear
Stress with B1
Bob
(dyne/cm
2
)
Color
Code
F0.2
77.2
0.2
307
Green
F0.5
193
0.5
766
Yellow
F1
386
1
1,533
Blue
F2
772
2
3,066
Red
F3
1,158
3
4,600
Purple
F4
1,544
4
6,132
White
F5
1,930
5
7,665
Black
F10
3,860
10
15,330
Orange
*With R1-B1 Combination