i saw you offered to calibrate another member's par meter, is that an open offer? when i build mine would you be willing to do the same for me?
Sorry, I'm busy with other projects and won't have time to calibrate your meter. Set the resistor to 24.7K and hope for the best.
What light source are you all calibrating to?
A regular white spiral bulb.
And use the smallest guage wire you can find. I'm using an ethernet cable. There are lots of variables if you use different materials so that's why having a PAR meter to calibrate against is good.
I'm getting PMs from science people who aren't even in planted tanks wanting to measure sunlight for their tomato plants
I think it works even better for sunlight since light bulbs are so varied and low in output compared to the sun.