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Cheap PAR meter hack - Use a Lux meter to measure PAR accurately

I have tested four cheap Lux meters from Amazon to see if they can be used to measure PAR (Photosynthetically Active Radiation) comparing them vs my other par meters. So you can use them to optimise your grow light setup. The measurements are compared to the benchmark quantum sensor for measuring PAR from Apogee which costs about $500. The results are surprisingly accurate.

The Lux meters were tested with the two most common spectrum in LED grow lights sold in the last few years, a 3500K or neutral white LED and a White LED with added red LEDs. Other grow light spectrum were not tested and thus hack will not work for HID or 'Blurple' led grow lights (with blue and red diodes only).

Each Lux meter reading was graphed against the benchmark quantum sensor readings. On the top of each chart is the factor to apply for each Lux meter to convert the lux readout to PAR in µmols/m²/sec.

For example if you are using the UNI-T lux meter and you have a white and red LED grow light you multiply the LUX readout by 0.017 for the PAR equivalent.

Buy the UNI-T UT383BT Lux meter here

Amazon Lux meter to PAR reading graph 3500K white LED 
Amazon Lux meter graph white +RED LED 

Lux meter specs: Light meter AP-881E light meter for plants Illuminance meter Lux meters with Display 3999(Range from 1~300,000Lux Mastech MS6612 Lux 1 to 200000 Uni -T UT383 Lux meter V resourcing Lux meter 1 200000 lux

Buy the UNI-T UT383BT Lux meter here

Buy the UNI-T UT383BT Lux meter here

 

Buy the UNI-T UT383BT Lux meter here

 

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5 thoughts on “Cheap PAR meter hack - Use a Lux meter to measure PAR accurately

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Andy Pay

Vince Milczewski,

Your Lux meter is displayed in a lower resolution. Multiply your uni-T reading by 10. Then multiply by 0.017. That will give you the correct number

August 31, 2023 at 14:22pm
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Matt Weier

oops – I guess you were right about 0.17 for white with red leds. 0.14 is for white-only.

August 31, 2023 at 14:22pm
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Matt Weier

@Vince – I found the same thing and noticed that the factor of 10 that it’s off is because the Uni-T Lux meter has a tiny little “x10” indicator in the corner. So when you go to multiply by .014 (NOT 0.017) you are also first multiplying the numbers on the meter by 10.

So short answer is yes, if you see “x10” on the meter, multiply lux by 0.14 not 0.014 to get PPFD

August 31, 2023 at 14:22pm
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Dizwire

Same here, Vince. My Uni-T calculated PPFD seems to be off by a factor of 10 if I multiply LUX by .017 and not .17.

August 31, 2023 at 14:22pm
t4s-avatar
Vince milczewski

Hey bud, I bought the uni-t because I seen ur videos. After reading ur finding it says to take the LUX and multiply it by .017 I get. Avery low number and my park should be way higher. Do I multi lot by .17 or .017 because removing 1 decimal place seems to be a lot closer to what I was expecting? Thanks for any info u could give me. Your YouTube videos are very helpful, thanks!

June 13, 2023 at 12:59pm

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