LoRa MER Week 3.5: Testing Turbidity and Posting Data to Internet

RE: LoRa MER Week 3.5: Testing Turbidity and Posting Data to Internet

shabaz — Fri, 04 Jan 2019 16:03:32 GMT

Hi Frank,

This project is looking great!! Interesting sensor too.. as you say, maybe the rubber/foam reduces ambient light.

I don't know if it is helpful (I know nothing about this topic), maybe photo filter samples (you can get a book of several hundred samples for little cost) could have useful capability for a crude calibration. This type of stuff basically (I've not used this one):

https://www.amazon.com/Rosco-Lux-Small-Swatchbook/dp/B0002ER2YG

There are usually neutral filters for (say) 10% reduction, 20% reduction, etc.. I'm not super familiar with the photography stuff, but [mention:6f7924a04a1349b2ac17b4cde35daef5:e9ed411860ed4f2ba0265705b8793d05] and [mention:2136c4649d3b47f78653b7e97ac61f69:e9ed411860ed4f2ba0265705b8793d05] are, they may know.

RE: LoRa MER Week 3.5: Testing Turbidity and Posting Data to Internet

fmilburn — Sat, 22 Dec 2018 04:14:05 GMT

On reviewing this, I thought the points I plotted on the NTU graph should be clarified. As noted in the discussion, my samples are not calibrated so only the NTU value of the tap water, which should be very low, is known. Assuming the graph in the datasheet gives the limits for sensor output, there is a range of NTU that the output voltage might represent. The plot as presented above assumes the data follows the slope of the limits on the plot but I don't know this to be true. A better representation might be this:

[View:/resized-image/__size/620x460/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-dab90e34-47fc-486f-aa90-1517108a83e3/6232.contentimage_5F00_189541.jpg:620:460]

But in truth, I don't know how to interpret the output at this point and will treat it as directionally representative only.

RE: LoRa MER Week 3.5: Testing Turbidity and Posting Data to Internet

genebren — Fri, 21 Dec 2018 17:21:14 GMT

Frank,

Great update on your MER project. The turbidity measurements are very interesting and might be useful to me in my Master Naturalist volunteer efforts where we sometime setup experiments for the kids to sample water. I will have to follow along and see where this goes. It is a little strange how loosely specified the sensor behavior is, given the simple graph with two lines. I guess the good news it that your test fell between the lines. Hard to say what the difference of the plots indicate, maybe a range of temperatures,voltage, phase of the moon?

Good luck,

Gene