The Apogee SQ-610 ePAR quantum sensor measures the extended 400-750 nm range including far-red, accurate under all light sources including LEDs. Choose the output for your system.All versions share the same research-grade ePAR detector; only the output differs.Available Options Unamplified analog, 5m cable (SQ-610-SS) USB smart sensor with software (SQ-616) SDI-12 digital output, 5m cable (SQ-617-SS) Modbus digital output, 5m cable (SQ-618-SS) Key Features Extended spectral range 400-750 nm +/- 5 nm Calibration uncertainty +/-5%, drift under 2%/yr Cosine-corrected, waterproof NIST-traceable, 4-year warranty Made in the USA and backed by Apogee's industry-leading warranty and support. Ideal Applications Continuous ePAR canopy monitoring under LEDs Controller and datalogger integration Photobiology and far-red studies