Determining DLI (Daily Light Integral) from PAR

Here’s a good reference:

http://www.extension.purdue.edu/extmedia/HO/HO-238-W.pdf

Adapting the formulas on page 4, for starting with PAR readings that can be recorded with our loggers:

  1. Calculate the average PAR for the day: this would be the sum of all the PAR readings for the day divided by the number of PAR readings for the day. This would be 1440 readings for the day at a 1-minute logging interval, or 144 readings at a 10-minute logging interval. You could also use the averaging feature of the HOBO loggers to do some of the averaging. For example, you could set the logger to sample every minute, and log the averages every hour. Then there would just be 24 hourly readings to average in Excel.  
  2. Multiply the average PAR for the day by 0.0864 to get DLI.

 

Measurement and accuracy