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API test kit colour reading

5K views 7 replies 4 participants last post by  JDM 
#1 · (Edited)
I've been having some issues reading the colours as under different light and angles with shadows and whatnot, the colour seems to be close to one level or close to another, particularly the high range pH. Part of the issue is that the colour is not very dense so it is easily affected by the light and shadows etc.

Yesterday I was looking at the ammonia test and thought that it might be another non-zero, slight green to the test water. When I used a white light it looked more yellow. So I popped off the cap, set it on a white paper and read the colour looking down through the length of the tube. The colour is far denser and much easier to read... and was a really nice yellow with no hint of green.

This leads me to think that my very low, non-zero readings have been zero more often than not. Although there is always some level of ammonia in the water just due to the nature of it's production and consumption cycle, I'm not sure that those levels would be high enough to register.

Anyone else read their tests that way?

Jeff.
 
#2 ·
That's probably the best way to read the color, particularly if you use a while piece of paper for a background. I always try to read the results in natural sunlight or under a "daylight" spectrum fluorescent bulb.
 
#3 ·
I hold the tube on the white background portion of the color card and go near a window to read it. Natural light seems to be the easiest way to compare the color.
 
#4 ·
Yah, but it's tough when I do most of my testing early morning or evening when there is no natural light. That and my test card colours are off, the nitrite zero is definitely wrong and I wonder if whatever the colour shift is affects the other card colours as well. I know what zeroes are for ammonia, nitrite and nitrate, my pH is never easy and doesn't match anything and the hardness is a straight colour shift drop count at least.

Jeff.
 
#6 ·
There is an offset yellow in the blue nitrite zero and I had someone else take shot of theirs to post here. I know that all cameras are not the same so I asked for a iPhone 4 shot so it should be relatively close when viewed on the same screen. They were not the same at all. It's a print process issue.

Jeff.
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#7 ·
I'm having trouble reading mine too. I just got the API liquid nitrate test and tested my tap water. If I hold the test tube in good light with the white card as background but an inch or so behind the test tube it looks orange, like 20ppm. But if I hold the test tube right against the card it goes a deeper red and looks 30-40ppm. Not sure which is correct.
 
#8 ·
Try the standing it up on the card and looking down trick. Because the colour is more opaque due to 2 or 3" of coloured liquid as opposed to the 1/2" through a curved glass surface... there just is far less refraction and less likelihood of picking up other stray colours.

The other thing I find is that doing this lets me put it beside only one colour at a time negating the issue of another colour also being beside it.

I should try this on the pH to see how it works... that's the toughest but also the least concerning so i haven't fretted over it.

Jeff.
 
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