USB Smart Quantum SQ-420X PAR Sensor

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PAR (photosynthetic active radiation) is the easiest way to measure the available light for corals consume and use for photosynthesis. With LED lights giving more and more control to the consumer the best thing is a PAR meter that is affordable and simple to use. With PAR readings you can monitor light degradation, clarity of water, and intensity of the lighting schedule. Most LED lights out on the market today have more power than what your corals can take and will quickly bleach out from too much light. By having a PAR meter to monitor the light intensity you will have tangible numbers to go off of, instead of just guessing.

The SQ-420X USB Powered Quantum PAR Sensor is a valuable piece of equipment that can connect right to your windows or mac based PC that will read and record PAR data. PAR meters used to be a few hundred dollars for a simple, entry-level PAR sensor and now the SQ-420X has revolutionized the industry, allowing you to use your own computer instead of having to purchase a dedicated module or extra piece of equipment just to read what the sensor is seeing.

We personally like inputting all of our readings into a spreadsheet to make a chart of light output, as well as overlay the readings on a photo as well. Having a picture with your tanks PAR levels is very handy to have when placing new corals in your tank.

  • Resolution - 0.1 µmol m-2 s-1
  • Calibration Factor - custom for each sensor and stored in the firmware
  • Measurement Repeatability - less than 1 %
  • Response Time - software updates every second
  • Field of View - 180°
  • Spectral Range - 410 nm to 655 nm (wavelengths where the response is greater than 50% of the maximum; see Spectral Response Graph in Images)
  • Dimensions - 2.4 cm diameter and 2.8 cm height
  • USB Cable - 4.6 m (15 ft)
  • Current Draw (when Logging) - 5.1 mA
  • Warranty - 4 years



Software Downloads:

Apogee Connect for Windows

Apogee Connect for Mac OS

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Product Questions

What is the best selfie stick for this??
Question by: John Flurkey on Nov 20, 2023, 2:38 PM
The best option to use is the Apogee Sensor Wand!


I hope this helps!
Answer by: Taylor L. (BRS Staff) on Jan 19, 2024, 10:35 AM
I recently purchased the Kessil 360X Tuna Blue, just not sure which version Par meter to purchase? Do I need the SQ-420 or the SQ-520? The $200ish price difference makes me ask this question.
Question by: Richard Hoose on May 19, 2022, 2:17 PM
The SQ-420 (https://www.bulkreefsupply.com/usb-smart-quantum-par-sensor-apogee.html) connects to your personal computer so that you can track your information in a spreadsheet using their application whereas, the MQ-510 (https://www.bulkreefsupply.com/mq-510-full-spectrum-underwater-led-par-meter-apogee.html) has an attached meter which is more appropriate if your tank isn't accessible to your computer.
Answer by: Scott F. (BRS Staff) on May 19, 2022, 5:35 PM
Hello according to apogee, the original sensors have a new version from June 1st on, is this model the 420 or 420x which is the model launched last June 2021?


Question by: Cristiano Frade on Mar 28, 2022, 12:40 PM
Hey there,
Thank you for reaching out to us. This model is the SQ-420.

Please let me know if you need anything further and take care!
Answer by: Matt Lucero (BRS Staff) on Mar 29, 2022, 9:44 AM
what is the thread pitch on the screw?
Question by: walter p maguire on Jan 27, 2022, 12:49 AM
The screw size to attach the sensor to the wand is 10-32 x .625
Answer by: Matt Lucero (BRS Staff) on Feb 9, 2022, 9:26 AM
Will this USB PAR Meter work with a chromebook?
Question by: Stephen M. on Sep 25, 2019, 12:46 PM
Hey there,
Currently, the software is only available for Mac and Windows operating systems. There is a possibility that there may be an app for Chrome OS in the future, but at this time we do not know of any compatible application for Chrome OS and the Apogee software.
Take care!
Answer by: Charlie on Sep 25, 2019, 2:16 PM
When will the Mac version come out? all I need is a computer correct?
Question by: Steve on Mar 25, 2016, 5:40 PM
Great question!
According to Apogee's site there is current a Mac Software available right now. I have included a link below to the webpage with the software download. For set up you will simply plug in the sensor to your computer and pull up the program. Feel free to let us know if you have any further questions!
Answer by: Connor on Mar 28, 2016, 11:04 AM