Testing Instrument Quality and Troubleshooting

In theory, the two background spectra used to calculate the 100% line should be identical because they were measured on the same instrument under the same 

FIGURE 2.30 An FTIR 100% line. Sixteen scans and 8 cm resolution were used. The data used to calculate the slope of the line are indicated. 

For this particular 100% line the peak-to-peak noise between 2200 and 2000 cm is (99.961% - 99.928%) = 0.033%. This is an excellent result for this particular spectrometer. The results you obtain will depend upon your FTIR and the number of scans and resolution used to measure the 100% line. Your FTIR software may use a different unit of noise measurement than used here, such as RMS (Root Mean Square) noise. Consult with your manufacturer about what noise levels are typical for your FTIR. 

Your FTIR software package may have a validation or calibration function that may automatically run some or all of the tests noted here. This is line because it saves you the trouble of running the tests yourself. However, you should familiarize yourself with what tests are run, where the results are stored, and what the numbers mean. You must look at this data on a regular basis to check for any disturbing trends. Just because the computer runs the tests for you does not mean you can sit back and ignore the data. 

Dorothy Michelson Livingston, The Master of Light A Biography of Albert A. Michelson, University of Chicago Press, Chicago, 1973. 

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