Figure 20-36 shows standard uncertainty for measurements of carbon monoxide using averaging times of 11 to 1 000 s. 1000 s.
a. Figure 20-36 is a log-log plot. Read the standard uncertainty for 44 and 1616 s of signal averaging off the graph.
b. Based on a value of 1.18 ppm 1.18 ppm for 1 s 1s of signal averaging, what are the expected standard uncertainties at 4 4 and 16 s 16s  in an ideal experiment?
c. What standard uncertainty is predicted if signal is averaged for 100 s 100 s ? Does this agree with the experimental results in Figure 20-36?
d. Why does standard uncertainty increase when averaging for 200200 or more seconds?

Figure 20-36

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Standard uncertainty (ppm CO by volume) 3.0 1.0 0.3 0.1 0.03 O O 10 3 O Signal averaging reduces uncertainty 00000000 Drift increases uncertainty 300 Aff 1 000 100 10 30 Signal averaging time (s) Harris/Lucy, Quantitative Chemical Analysis, 10e, 2020 W. H. Freeman and Company FIGURE 20-36 Decrease in standard uncertainty in nondispersive infrared measurement of 31.8 ppm CO 31.8 ppm CO in air with increasing number of measurements averaged. Measurement rate with diode laser = 1 Hz, 1 Hz, so 100 $100s of signal averaging time=100.100 signals averaged. Standard uncertainty decreases by a factor of 1010 when 100100 signals are averaged.