Welch Allyn Duet CO2 Module - User Manual - Manual (Page 15)

Duet CO
2
Module OEM Implementation Manual
Welch Allyn OEM Technologies Confidential Page 15
Pressure transducers
The barometric pressure circuitry monitors pressure via transducers in order to compensate for the
effect of pressure variation on CO
2
measurements. The transducers include:
§ an absolute pressure transducer which monitors the ambient pressure for pressure broadening
effects on the CO
2
signal.
§ a second absolute pressure transducer that monitors internal bench pressures.
§ a differential pressure transducer that is used for pump flow regulation.
Mainstream Components
The functional components necessary for mainstream operation include
§ mainstream daughter board
§ flex circuit with Nicolay receptacle
§ mainstream sensor
§ airway adapter
Mainstream Daughter Board
The mainstream daughter board, or mainstream stick, provides controls to start and maintain the
chopper motor speed; controls to regulate heater output and monitor sensor temperature; and logic for
mainstream fault sensing.
The functional components of the mainstream daughter board include the motor control hybrid, the
heater control circuitry and the flex circuit connector.
The motor control hybrid operates via drive coils in the chopper motor to provide feedback to the
microprocessor to drive the motor. The microprocessor uses this signal to synchronize the waveform
signal with the chopper motor and to start and maintain the motor speed.
The heater control circuitry controls the heater output and monitors internal bench temperature. A
signal from the microprocessor is applied to the heater element in the sensor head. A thermistor
located in the sensor housing provides temperature feedback to the heater control. This feedback is
used to control the sensor housing temperature.
The heater power supply uses a pulse width modulated, or PWM, signal to step down the raw input
voltage to a level appropriate for maintaining the mainstream sensor at 42
o
C.
The flex circuit connector on the mainstream daughter board provides electrical connection of the flex
circuit to the mainstream daughter board.
Flex Circuit with Nicolay Receptacle
The flex circuit with Nicolay receptacle interfaces the mainstream sensor to the mainstream daughter
board.
The functional components of the flex circuit with Nicolay receptacle include the Welch Allyn OEM
Technologies flex circuit, or flex circuit, and the Nicolay receptacle.