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  • An Inexpensive Photometer and Colorimeter

    I tried it with a black bucket over it in a dark room too. Ambient light was registering 0. Still got no luck with any ratios

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  • An Inexpensive Photometer and Colorimeter

    I took a few samples today on a PalinTest benchtop photometer using 1 blank and 4 different samples. I got the transmittance of the 4 samples at 520nm and 570nm. I also used my photometer to read the transmittance of the 4 samples with the 520nm and 570nm LEDs.I put these values into Excel and calculated the absorbance, 2-log(%T).I tried getting the absorbance ratios and plot them on a graph, but the plot was pretty random, no trend line would fit anywhere close. I tried the method that I mentioned above (The pH seawater photometer project) by getting the absorbance ratios, but this too didn't make a nice plot with a nice trendline.Any help would be great.

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  • An Inexpensive Photometer and Colorimeter

    Hi. I haven't really got a housing yet, I'm still testing at the moment.My test setup is basically a piece of 1 inch diameter plastic pipe about 40mm high. It has holes drilled in one side for the 2 LEDs and one in the opposite side for the TSL2561.To measure, I currently take 5 samples of the blank with the LED on, and 5 samples with the LED off (ambient). I order each of the 5 samples from big to small, remove the top and bottom and average the middle 3. I then take the ambient reading away from the reading I got with the LED on. I then do the same with the sample.It may look a bit crude at the moment, but it seems to work pretty well under normal indoor ambient light, giving repeated readings the same for the same sample. If the sun is coming through the window onto to top of the cur...

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    Hi. I haven't really got a housing yet, I'm still testing at the moment.My test setup is basically a piece of 1 inch diameter plastic pipe about 40mm high. It has holes drilled in one side for the 2 LEDs and one in the opposite side for the TSL2561.To measure, I currently take 5 samples of the blank with the LED on, and 5 samples with the LED off (ambient). I order each of the 5 samples from big to small, remove the top and bottom and average the middle 3. I then take the ambient reading away from the reading I got with the LED on. I then do the same with the sample.It may look a bit crude at the moment, but it seems to work pretty well under normal indoor ambient light, giving repeated readings the same for the same sample. If the sun is coming through the window onto to top of the curvette, it doesn't like it too much.I have used this type of ambient light reading technique in another project, an RGB LED interactive table. Or 'the Magic table' as my 4 year old calls it :)Anyway, I've got access to a PalinTest 7100 at work, so I will take a few samples with it and also take the samples on my one with the 2 different LEDs. Then using the transmittance I record from each LED, should be able to build up an equation to make it read the same as the PalinTest.

    Thanks for the reply. After posting on here, I came across another website which talks about using 2 LEDs and obtaining a ratio from them.A sea water pH meter that is accurate to 0.01pH...http://www.sciencedirect.com/science/article/pii/S...So, does this sound like I'm on the right track...As I have another LED in my system (570nm) for calculating alkalinity, I guess I should use the PalinTest 7100 I have access too, take samples on that and use the same samples on my device using both LEDs and work out the ratio from the readings. Then use Excel to create a scatter graph of the two, then get the equation of the line. I can then use the equation to match my readings to the PalinTest.Little bit more work to do, but it's very interesting stuff :)

    Hi. I haven't really got a housing yet, I'm still testing at the moment.My test setup is basically a piece of 1 inch diameter plastic pipe about 40mm high. It has holes drilled in one side for the 2 LEDs and one in the opposite side for the TSL2561.To measure, I currently take 5 samples of the blank with the LED on, and 5 samples with the LED off (ambient). I order each of the 5 samples from big to small, remove the top and bottom and average the middle 3. I then take the ambient reading away from the reading I got with the LED on. I then do the same with the sample.This seems to work pretty well under normal indoor lighting. If the sun is coming through the window onto to top of the curvette, it doesn't like it too much.I have used this type of ambient light reading technique in anothe...

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    Hi. I haven't really got a housing yet, I'm still testing at the moment.My test setup is basically a piece of 1 inch diameter plastic pipe about 40mm high. It has holes drilled in one side for the 2 LEDs and one in the opposite side for the TSL2561.To measure, I currently take 5 samples of the blank with the LED on, and 5 samples with the LED off (ambient). I order each of the 5 samples from big to small, remove the top and bottom and average the middle 3. I then take the ambient reading away from the reading I got with the LED on. I then do the same with the sample.This seems to work pretty well under normal indoor lighting. If the sun is coming through the window onto to top of the curvette, it doesn't like it too much.I have used this type of ambient light reading technique in another project, an RGB LED interactive table. Or 'the Magic table' as my 4 year old calls it :)

    I stumbled upon this instructable after making my own photometer and am having a slight issue. I have a question if someone could answer please.I am using a 520nm LED to measure the transmittance/absorbance of a solution which has a DPD1 tablet crushed in it (Chlorine). I am measuring the blank, then measuring the sample and calculating the transmittance. Then using graphs I produced from an old PalinTest 5000 manual I display the chlorine content.All works pretty well and I get exactly the same reading every time, but the problem is, when I compare my photometer to a proper PalinTest photometer, my transmittance is about 4% higher. (eg. If the PalinTest photometer shows 60%T, mine would show 64%T), which is quite a difference.I understand that the LED I'm using has a dominant wavelengt...

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    I stumbled upon this instructable after making my own photometer and am having a slight issue. I have a question if someone could answer please.I am using a 520nm LED to measure the transmittance/absorbance of a solution which has a DPD1 tablet crushed in it (Chlorine). I am measuring the blank, then measuring the sample and calculating the transmittance. Then using graphs I produced from an old PalinTest 5000 manual I display the chlorine content.All works pretty well and I get exactly the same reading every time, but the problem is, when I compare my photometer to a proper PalinTest photometer, my transmittance is about 4% higher. (eg. If the PalinTest photometer shows 60%T, mine would show 64%T), which is quite a difference.I understand that the LED I'm using has a dominant wavelength of 520nm, but I assume it is also putting out light above and below this. The PalinTest uses bandpass filters in it, which are probably more accurate than my LED.What would be the best way to get a more accurate reading of the transmittance?

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