Owner manual

Brookfield Engineering Laboratories, Inc. Page 39 Manual No. M/98-211-A0701
1. Casson (Standard)
The Standard Casson equation is:
√
τ =
√
τo +
√
η D
where:
τ
o
= Shear Stress
τo
= Yield Stress (stress at zero shear rate)
ηD
= Plastic Viscosity
D
= Shear Rate
The calculated parameters for this model are:
Plastic Viscosity (cP or mPa•s)
Yield Stress (Dynes/cm2 or N/m2)
Confidence of Fit (%)
The Standard Casson method is a direct implementation of the original Casson equation.
2. NCA/CMA Casson (Chocolate)
This Casson method is derived from the standard set forth by the National Confectioners
Association (NCA) and the Chocolate Manufacturers Assocation (CMA). Although based on the
original Casson equation, this implementation has been tailored by the NCA and CMA
specifically to applications involving chocolate.
The Chocolate Casson equation is:
(1+a)√τ = 2√τo + (1+a) √ηD
where:
τ
o
= Shear Stress
τo
= Yield Stress (stress at zero shear rate)
ηD
= Plastic Viscosity
D
= Shear Rate
a = spindle (or bob) radius/ inner cup radius
The calculated parameters for this model are:
Plastic Viscosity (cP or mPa•s)
Yield Stress (Dynes/cm2 or N/m2)
Confidence of Fit (%)
3. Bingham Plastic
The Bingham equation is:
τ = τo + ηD
where:
τ
o
= Shear Stress
τo
= Yield Stress (stress at zero shear rate)
ηD
= Plastic Viscosity
D
= Shear Rate
The calculated parameters for this model are:
Plastic Viscosity (cP or mPa•s)
Yield Stress (Dynes/cm2 or N/m2)
Confidence of Fit (%)
4. Power Law
The Power Law equation is
τ = kD
n
where:
τ
o
= Shear Stress
D
= Yield Stress (stress at zero shear rate)
k
R
= Plastic Viscosity
n = Shear Rate