High Speed Length Controllers Instruction Manual
Model: 315D | 322D
© Aurora Scientific, 2020 VER. 1.00
page 7
3
General Operating Procedure
The high-speed length controller will drive the arm position to match the length input signal. The actual
arm position is provided at the LENGTH OUT connector. The front panel voltmeter provides an indication
of the actual arm position. (Note: since the voltmeter only updates two times per second the output of
the meter is an average and it will not accurately indicate high-speed movements.)
3.1
Controlling and Measuring Length
LENGTH IN controls the position of the tip of the lever arm such that a positive signal rotates the arm in a
clockwise direction, and conversely, a negative signal counter clockwise. The maximum length input
signal is
10V.
LENGTH OUT is a bipolar signal that swings symmetrically about zero volts. The center of the mechanical
range is when LENGTH OUT is at zero volts. Try to make use of the center portion of the range rather
than just one side of the mechanical center. A clockwise rotation of the shaft causes LENGTH OUT to
become more positive, and conversely a counter clockwise rotation more negative. A length change can
be accomplished by either turning the LENGTH OFFSET knob located on the front panel or by inputting a
signal to the LENGTH IN connector. Both LENGTH IN and LENGTH OUT have the same scale factor which
is shown in the specifications section.
3.2
Controlling Force
High-speed length controllers cannot control force by themselves. Aurora Scientific has a digital
controller available that interfaces with a high-speed length controller and a force transducer and allows
the user to control force. Our model 600A Digital Controller can generate critically damped force clamps
in as little as 1.5 msec.
The 600A Digital Controller includes a PC computer, data acquisition card, signal interface, all necessary
cables and custom software. The software runs under a real-time Linux operating system and includes all
the standard muscle physiology test protocols. Custom protocols can be generated using the on-screen
test editor. In addition to controlling the high-speed length controller the software also collects data
from the length controller and a force transducer and provides digital I/O to control other instruments
such as stimulators. For more information please
3.3
Controlling the System with External Electronics
Most experiments will require that LENGTH IN be driven with an external electronic device. The cost of
computers and data acquisition circuit boards have dropped to such a level that they are the best way to
control a high-speed length controller. One analog input and one analog output are all that are required
to control the instrument. Analog-to-digital resolution of 12 bits (1 part in 4096) is adequate however a
resolution of 16 bits is preferred. A 600A Digital Controller provides a complete data acquisition and
control capability as a turn-key system.
