Correction Of Dynamic Measurement - Thermo Scientific HAAKE RotoVisco 1 Instruction Manual

Hints on Measurement

14.3 Correction of Dynamic Measurement

(RheoStress 1)
Description of the problem
There are two important influences:
Mechanical influence:
 additional frequency dependent phase shift caused by
inertia I of the rotor (as well as by the damping D and
the spring constant K of the measuring system).
Electro-magnetic interactions:
 frequency dependent phase shift  between the cur-
rent in the motor coil and the torque acting on the axis.
 reduced motor torque (M
(and current) dependent induction effects in the coil.
Consequently, we have to correct two quantities in the rheo-
logical equations:
 phase angle 
 corrects for electromagnetic effects,
mechanical influences on the phase shift can be
corrected by taking into account I, (D), (K).
 acting torque on the axis M
 corrects for electromagnetic influences on the
torque amplitude.
Quantities we assume to be well-known or measured exactly:
 inertia I (determined by a creep experiment without
sample),
 damping constant D and spring constant K of the sys-
tems (both have only a negligable influence),
 A- and M-factors of the measuring system (sensor),
 rotation angle  measured with the optical encoder.
Indices used:
exp
me
(without)  corrected data
135
()<M
d
d
 original measuring data
 quantities corrected for electromagnetic
but not for mechanical (inertia) influences
) due to frequency
0