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4.2 Force transducer calibration
As a part of the general maintenance of the myograph, DMT recommends that the
myograph is weight calibrated at least once every month. DMT also recommends that
the myograph is weight calibrated every time the system has been moved or has not
been used for a long period of time.
Principles of weight calibration
Weight calibrating the force transducer is based on simple physics: the net torque
acting on a balance when applying a certain amount of weight. The magnitude of the
torque τ about a point of rotation P is defined by:
r
F
P
θ
τ = r · F · sinθ
where r is the distance from the point of rotation to the point on the object where
the force F is acting with the angle of θ. Applying the physics to the weight calibration
setup is illustrated in Fig. 4.5.
Arm
Pan
(PA)
FW
Transducer Arm (TA)
rPA
τ
rTA
FT
Figure 4.5 Theoretical principle of the weight calibration
Applying the weight on the pan arm creates a net torque acting at the “center of gravity” resulting in a force FT acting on the force transducer. The following two equations
describe the forces working in the weight calibration system:
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Chapter 4
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