Logging Ratios of Spectral Bands

The LI-180 can compute ratios of spectral bands and record the results in the data file. In this tech tip, we provide basic instructions for accomplishing this.

1. In the Home screen, select WAVEBANDS.
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2. For this exercise, we'll create two custom bands.
   1. Edit the range for Custom1 so that it includes photosynthetically active radiation and the far-red (PAR+FR; 400 - 710 nm).
   2. Edit the range for Custom2 so that it includes the far-red (FR; 700 - 710 nm).
   3. Change the names to PARFR and FR or whatever you like. The name and range will be included in the data file.
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   4. Tap the Home button to exit.
3. Next, select RATIOS.
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5. You can name the ratio to identify the column in the data file; it won’t affect the measurement values.
4. Select wavebands to use for the ratio.
5. The options include five default wavebands, the four custom wavebands, and the final item called “clear.” The ratio is computed as FR / (FR + PAR).
   1. Tap the upper left rectangle and select the waveband that is the numerator of the ratio (FR; 700 - 710 nm).
   2. Tap the upper right rectangle and select the second band to use for the denominator of the ratio (PARFR; 400 - 710 nm).
   3. 
   3. Tap the Home button to exit.
5. Configure data logging.
   1. From the home screen, tap the down arrow to view the second page.
   2. Tap the LOGGING button and set the parameters.
   3. Log the data by pressing the log button or configuring automatic logging.
6. Download the file to your computer (See Downloading data from the LI-180). 
7. The ratio is stored in a column in the data file.
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