Technical manual
KANMED Operatherm OP3
Page
7
of
34
OP3-099 Calibration
Adapter
6 Technical Information
General
The Control Unit contains a microprocessor based heating control system that regulates the
temperature of each of the 8 elements (heating zones) of the Heating Pad. The temperature is
continuously monitored and the calculated average temperature of the heating pad is displayed.
The safety system in the Control Unit is continuously monitoring the main power, internal voltages,
running parameters, the pad condition and the behaviour of each element.
Two autonomous safety circuits, totally independent of the microprocessor based operating system,
can at any time stop the warming, should conditions occur that can cause over temperature.
If a fault is detected, the Control Unit will alarm visually and acoustically and switch off the
heating. The type of error is indicated on the alarm display. A description of the error codes are
found under the chapter “Trouble Shooting”.
Detailed system description.
The Operatherm OP3 system is designed with multiple level of protection against any foreseeable
errors that may cause potentially harmful conditions for the patient. The system is computer
controlled, with a fail safe (twin state) watch-dog, monitoring the correct operation of the main
process and will cause a safety relay to break the power to the pad if a computer error occurs. The
computer constantly monitors the running state of all vital parts of the system, and will
immediately report an error if any parameter runs outside its stated boundaries.
The calculated temperatures of the eight (or four) heating pad elements are based on individual
simultaneous measurement of the voltage and the current to each of the elements by two
independent A/D-converters. From these measurements the elements actual resistance is
calculated, and compared to the nominal resistance value programmed into the pads PROM
memory at calibration. The temperature coefficient of the element is also read from the PROM.
Based on this input, the elements current temperature is calculated (average value of the elements
area). Several comparative reference measurements are being performed in order to assure both
A/D converters integrity. If any discrepancy occurs, the system will break the power to the pad,
indicate the error and sound the alarm.
The measuring voltage fed to the pad is only 5V DC and one measuring slot is typically 10 ms long
(8.3 ms at 60 Hz). A full measuring/heating cycle is 18 pulses long, and 2 of these are always 5V
DC measuring pulses, leaving a maximum of 16 (of each 18) pulses available for heating.
The Pad element heating voltage is unregulated rectified 28V AC (typically), generating one
hundred pulses per second (one hundred and twenty at 60Hz mains voltage). Eight individual
temperature protected semi conductor switches, with built in error supervision, are being used to
gate the required number of heating pulses to each of the eight elements. (This regulating method
gives the ability to a linear individual control of the heating power to each of the elements from 0.1
to 23.0 W). Maximum power is however only permitted during 10 minutes from start. After this
time-out, the system will limit the output to maximum 11 heating pulses in each 18 pulse cycle,
(corresponding to max. 16 W/element).
