User guide

Charnwood Dynamics Ltd. Coda cx1 User Guide – Coda Basics I - 1
CX1 USER GUIDE - COMPLETE.doc 26/04/04 30/162
Operation
When the scanner unit is not acquiring data (i.e. when the yellow LED on the scanner unit
is not illuminated) very little current is being drawn from the batteries in the drive boxes.
However, as soon as the scanner unit starts to send out control signals to the marker
drive boxes (i.e. with the yellow LED now on) the rate of current consumption rises to
about 50mA in each of the drive boxes if they have two LED markers attached. This
current is principally used by the marker LEDs which are being pulsed with current pulses
of duration 40 microseconds at up to 800Hz repetition rate. The capacity of the batteries
in the drive boxes is 30mA hours. This is sufficient for at least 100 data acquisition runs
before the batteries need to be recharged.
Recharging the Marker Drive Boxes
Recharging should be done by first ensuring that both LED markers are disconnected
from the drive boxes. The drive boxes should then be placed in the charger unit for
overnight charge at the end of each working day. To do this, place each drive box in a
charging bay of the charger unit, ensuring that the prongs of the charging connector are
properly inserted into one of the sockets on the drive box. It does not matter which of the
two sockets are used. Proper connection is confirmed by the red LED above the charger
bay. When all the drive boxes have been placed in the charger unit you should initiate the
12 hour charge cycle by pressing the red button marked ‘Start’. You will see the LED
adjacent to the Start button light up. When the 12 hour charge cycle is complete this LED
goes out and the unit is then in trickle charge mode.
When the Codamotion system is not in use the marker drive boxes should be left in the
charger unit and the charger unit should always be left switched on. This ensures that the
batteries are kept in a full state of charge ready for their next period of use. Never leave
the marker drive boxes unconnected to the charger after use as the small current which
the internal circuitry uses, combined with the battery’s self discharge will mean that the
batteries run down within a few hours. It is quite safe to leave the batteries on trickle
charge indefinitely.
Using the Markers
When using the markers for acquiring movement data it is important to understand that
the Coda scanner unit must have an unimpeded view of the LED markers and their drive
boxes. Both the drive boxes and the LEDs have a field of view which encompasses a
solid angle of 180 degrees.
This is more than adequate for most applications. However it is important to be aware
that if the LED markers or the drive boxes are rotated to the limit of their angular field in
relation to the scanner unit then the markers may disappear from the view of the system.
Attaching the Markers
Markers and their associated drive boxes are attached to the subject being studied using
medical double sided adhesive tape. It is recommended that careful thought is given to
the siting of markers before starting to mount them on the subject. The field of view
considerations noted above and the relative siting of markers and drive boxes should be
taken into account. To assist in this, LED markers are provided with leads of different
lengths so that the appropriate length lead can be chosen to suit a given site on a subject
of particular size. Also bear in mind that it is quite permissible to use only one LED
marker with any drive box if connecting two is not convenient in a particular situation.