SI-H Muscle Testers
18
WORLD PRECISION IN STRU MENTS
In constant load experiments, the initial length of the muscle is set using the manual
adjustments of the muscle research platform. While the muscle is held at its initial length,
it is stimulated with tetanizing pulses so that the muscle develops its isometric force.
These stimulus pulses are controlled by the stimulation protocol created in
MDAC
and
sent from the analog stimulus output of the
LabTrax 8/16
. Once isometric tension is
established in the muscle, the capture command created in
MDAC
is sent from one of
the digital outputs of the
LabTrax 8/16
to the
SI-COLUB
module. This command triggers
the
SI-COLUB
to read the initial force (F
0
) in the muscle and monitor the actual muscle
tension through feedback provided by the force transducer and its amplifi er (
SI-BAM21-
LCB
) or its anti-oscillation unit (
SI-AOSUB
). The
SI-COLUB
analyzes the inputs that it
receives and calculates the command that needs to be sent to the
SI-MOTDB
Linear
Motor Controller to maintain a load on the muscle as it slacks and reaches the force (kF
0
),
where k is set by the
Force Step
dial.
The time it takes to reach this force is determined by the
Slack
potentiometer. Once kF
0
is reached, the
SI-COLUB
sends position commands to the motor to maintain that force.
When the desired time at kF
0
is elapsed,
MDAC
sends another command through the
same digital output of the
LabTrax 8/16
to the
SI-COLUB
module to return the muscle
to its original length and force (F
0
). The restretch time is determined by the Restretch
potentiometer.
The
SI-COLUB
offers three modes of operation: Constant Load, External Loop and Bypass.
SI-COLUB
Command
Linear Motor
Feedback
Measured Force
(from SI-AOSUB
or SI-BAM21-LCB)
External Trigger
(Like SI-SARCAM Camera)
Capture
Force Step
Bypass
×k
Constant Load Mode
External Loop Mode
Bypass Mode
Fig. 19 This block diagram graphically shows the three modes of operation in the Constant
Load module.
