THEORY 20Art: 714382-00D Rev. Date: 02/20/06 20-1ANALYZER FUNCTIONSIntroduction The i-STAT 1 analyzer is a microprocessor-controlled electromechanicalinstrument designed to:• identify the cartridge type.• control the flow of fluids within the cartridges.• mix sample and reagent (where applicable).• apply electrical signals to certain types of sensors within thecartridges.• control the temperature of the cartridge at 37°C (where applicable).• measure electrical signals generated by the sensors (cartridge and teststrip).• measure the barometric pressure of the surrounding environment(where applicable).• calculate concentrations of analytes using the generated electricalsignals.• display the results in numerical values and on bar graphs (whereapplicable).• communicate the results to a printer and computer.• sense and communicate operational errors.• maintain an internal clock/calendar.• store all test records, Electronic Simulator results and Quality CheckCodes and messages.MicroprocessorSystemThe microprocessor control system manages all functions of the analyzer. Itaccesses three types of memory storage devices. A “FLASH” EEPROM modulestores the software program in the analyzer. The RAM, which is backed upby an internal lithium battery, is used for temporary storage of sensor signalsmeasured during operation and for storage of test records. Another EEPROMstores factory calibration information, the instrument serial number andcumulative count of uses. Neither of the EEPROMs relies on the lithiumbattery for maintaining information.Sensor Interface Electrical signals from the cartridge sensors are conducted from the contactpads on the cartridge, through the internal connector in the analyzer, to thesensor interface circuit board. Electrical signals from the test strip sensor areconducted from the contact bars to a sensor interface circuit board. Thesecircuits amplify the signals from the sensors so that they can be furtherprocessed by the main electronic circuit board. Four signals are relayed to themain electronic circuit board from the cartridge sensor interface circuit board:
