Welch Allyn LC101 CO2 Module - User Manual - Manual (Page 10)

LC101 CO
2
Module OEM Implementation Manual
Page 10 Confidential Welch Allyn OEM Technologies
Measurement Compensation
IR absorption in the CO
2
wavelength band may be affected by a number of factors that alter the
CO
2
measurement. The LC101 Module automatically compensates for some of these factors
while others may be disabled by the host system.
These factors include
• water vapor
• pressure broadening
• gas mixing
• oxygen, nitrous oxide and desflurane or O
2
/N
2
O/desflurane
• Body Temperature, ambient Pressure and Saturated with water vapor or BTPS
Water Vapor
Water vapor compensation accounts for the effect that water vapor has on the IR absorption
characteristics of CO
2
molecules. During normal sidestream operation, CO
2
measurements are
adjusted mathematically to compensate for this effect.
The host may choose to disable this compensation when performing dry gas measurements in
which the gas does not contain water vapor. Dry gas procedures may include steady state
measurements and calibration procedures. Steady state measurements are performed only
when background CO
2
, or CO
2
present in the immediate environment, is measured. An example
of a steady state measurement is measuring the CO
2
content inside an incubator. Calibration
procedures use calibrated gas which is free of water vapor, or dry, as well.
The water vapor compensation is ON by default and may be enabled or disabled via a host
system command.
Pressure Broadening
Pressure broadening compensation accounts for the effect that barometric pressure has on CO
2
molecule distribution and is used in both measurement and autorun modes.
The pressure broadening compensation is ON by default and cannot be disabled by the host
system.
Gas Mixing
A small amount of gas “mixing” occurs as the CO
2
sample travels through the tubing to the
sample chamber. Gas mixing compensation accounts for the effect that low level gas mixing has
on the baseline, or InsCO
2
measurement in both measurement and autorun modes. The gas
mixing, or baseline, compensation is ON by default and can be disabled by the host system.