Teledyne gfc 7000ta operation manual Interference and Signal to Noise Rejection, Is reduced

Theory of Operation Model GFC7000TA Carbon Dioxide Analyzer

IR unaffected by N2 in Measurement Cell of the GFC Wheel and no additional CO2 in the Sample Chamber

CO2 MEAS

CO2 REF

IR affected by CO2 in Reference Cell with no interfering gas in the Sample Chamber

IR shinning through Measurement Cell of the GFC Wheel is reduced by additional CO2 in the Sample Chamber

M/R

is reduced

IR shining through Reference Cell is also reduced by additional CO2 in the Sample Chamber, but to a lesser extent

Figure 9-4: Affect of CO2 in the Sample on CO2 MEAS & CO2 REF

Once the Model GFC 7000TA has computed this ratio, a look-up table is used, with interpolation, to linearize the response of the instrument. This linearized concentration value is combined with calibration SLOPE and OFFSET values to produce the CO2 concentration which is then normalized for changes in sample pressure.

9.1.4. Interference and Signal to Noise Rejection

If an interfering gas, such as H2O vapor is introduced into the sample chamber, the spectrum of the IR beam is changed in a way that is identical for both the reference and the measurement cells, but without changing the ratio between the peak heights of CO2 MEAS and CO2 REF. In effect, the difference between the peak heights remains the same.

Teledyne Analytical Instruments 190