LED arrays; and workstation illumination
systems.
Optical device functions in these medical products include object in place verification; material dosage measurement;
liquid level detection; blood oximetry
measurement; bubble detection in fluid
tubing; high and low voltage circuit isolation; fluid flow rates; skin-care therapy
by controlled infrared and visible light
exposure; backlighting for X-ray and MRI
images; and workstation lighting.
Current sense resistors
Current sensing resistors use a simple
application of Ohm’s Law (Voltage =
Current × Resistance) to determine current draw. Resistors provide a predictable
and temperature-stable linear relationship between voltage and current in a
package that manufacturers are accustomed to specifying, purchasing and
assembling. The voltage drop across the
resistor usually provides a voltage signal
to an integrated circuit (IC). Manufacturers of medical electronics use current
sense resistors to ensure safe and efficient
operation of the battery packs for portable diagnostic and treatment equipment.
Current sense resistors in the battery pack
management circuits of professional-grade
portable defibrillators are one example of
this application. These battery packs are
capable of high current output, and must
be monitored to ensure safe operation and
a reliable charge state.
Current sensing ensures safe operation
by monitoring the current level during
This Hall-effect noncontact sensor is suited for
use with an array of medical equipment.
Sensor assemblies such as these enable detection of
the presence of fluids in medical devices.
the charge cycle of the battery. Excessive
current levels during battery charging may
indicate a battery malfunction or a short
circuit in the charging circuit. If the IC
senses a high voltage in excess of predetermined limits, the module may be shut
down to protect the safety of the users and
avoid destruction of the equipment.
The battery charge state may be monitored by tracking the net amp-hours of
battery use. During discharge of the
battery, the IC may monitor the current
levels (amps) and time of discharge, and
therefore calculate discharge amp-hours.
A similar calculation is available during charging periods. By tracking the net
amp-hours of use (the difference between
discharge amp-hours and charge amp-hours) and comparing this figure to the
capacity of the battery, a simple measure
of the remaining charge of the battery is
provided.
Potentiometers
In the field of medical diagnostic equipment, proper control and analysis requires
input from sensors that are near the
action. One example of sensor functions
that potentiometers serve is that of position control and sensing. Potentiometers
are used in a range of patient care equipment from table position controls for
X-ray, CAT and MRI machines as well
as position controls for dental chairs and
hospital beds.
One potentiometer design includes a
spring-return, linear actuated, conductive
plastic position sensor, which combines
a rugged housing with a proven ceramic
substrate to provide a workhorse mini-
ature position sensor for medical auto-
mation applications. The sensor exhibits
infinite resolution and a long life of five
million actuations. This robust design
eliminates the need for direct coupling in
medical applications, making the sensor
ideal for space-limited applications.
Stephen Oxley
M. Eng., C. Eng., MIET, is Senior Applications
Engineer
Rick Cronan
is Market Development Engineering Manager
David Winkler
is Business Unit Manager
and
Mike Torres
is Fixed Film Product Manager
all part of TT electronics plc,
Medical Team Europe
Europe: sales@ttelectronicseurope.com
Asia: sales@ttelectronicsasia.com
Americas: sales@ttelectronics-na.com
www.ttelectronics.com
