WPI SI-HTB, Инструкция по эксплуатации, Страница: 14 / 48

SI-H Muscle Testers
10
WORLD PRECISION IN STRU MENTS
Pulser Amplitude Adjustment Knob –When calibrating a force transducer, this knob
adjusts the amplitude of the pulser waveform so the display registers on the Signal
Amplitude Array .
Signal Amplitude Array –The 10-position LED array indicates the amplitude of the
transducer's response to the pulser's excitations. The LED array indicates when the
frequency of the square wave is equal to the resonance frequency of the force transducer.
Anti-oscillation Frequency Adjustment potentiometer – Use the included potentiometer
adjustment tool (WPI # 13661 ) to rotate the potentiometer until the force transducer
resonates. During this procedure, the number of segments in the Signal Amplitude LED
array that light up increases as the resonance frequency approaches that of the force
transducer.
External Input Port –The output signal from the transducer amplifi er comes into the
SI-AOSUB through this port. If the signal is not routed along the backplane, connect the
SI-BAM21-LCB Force Output to this port.
SI-SARCAM
Skeletal and heart muscles are composed of basic contractile units called sarcomeres.
Sarcomeres give these muscles their characteristic striated appearance.
Z-Lines
Sarcomere
Length
Fig. 9 Sarcomere units are arranged one after another within a muscle as shown schematically
here.
When a laser light is shined through the muscle fi bers, the light is diffracted in a pattern,
which is determined by the spacing between the muscle fi bers (sarcomeres). Because of
the sarcomere structure, the diffraction pattern looks similar to the pattern created by a
grating placed in front o f the light source. In muscle preparations, the monochromatic
light (from the laser), which strikes the muscle preparation on the perpendicular, is
diffracted according to the distance between the Z-lines of the muscle fi bers. Since the
Z-lines are like the bars in a grating fi lter, the diffraction distance is also know as the
grating constant. (Fig. 10)
Laser
Muscle Fiber
No Diffraction (center beam)
First Order of Diffraction
Second Order of Diffraction
First Order of Diffraction
Second Order of Diffraction
Fig. 10 As the light shines through the muscle fi ber, the sarcromeres diffract the light in a
pattern.
A red laser diode (

=650nm) is used. A one-dimensional (linear) CCD camera with a time
resolution of 1ms scans the light intensity of the diffraction pattern beginning 6.8mm
from the center beam. The camera scans only half the diffraction pattern, assuming that