Apogee's new DLI-600 meter is designed to measure photosynthetically active radiation (PAR) beyond the traditional 400–700 nm range. The DLI-600 measures the newly defined 400-750 nm ePAR radiation range, which has been shown to have extended photosynthetically active properties. In addition to measuring ePAR, the DLI-600 meter calculates daily light integral (DLI) and photoperiod. DLI refers to the total amount of PAR or ePAR incident on a plane in a 24-hour period, expressed in units of moles per square meter per day (mol m^-2 d^-1). Photoperiod is the total amount of time in which PAR or ePAR is incident on a plane during a 24-hour period and is expressed in units of hours (h). Both DLI and photoperiod influence plant growth and development, and they are often measured in greenhouses and growth chambers to aid in light management and decision making.

The DLI-600 meter has two different screen modes: stored data and live view data. In the stored data screen, it shows the DLI measurement, photoperiod, and which day the data was collected (up to 99 days ago). The live view data screen displays a running average of ePPFD from the last 2.5 seconds.

The DLI meters consist of a cast acrylic diffuser (filter), optical filter, photodiode, signal processing circuitry, and an LCD display mounted in an ASA plastic housing. DLI meters are designed for single or continuous measurements of PPFD or ePPFD; DLI; and photoperiod. The DLI meter uses a USB-C cable (included with the meter) to download the stored data as a CSV file to a computer.