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Old 03/19/2018, 07:44 AM   #1
fishkeeprian
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Hanna low range phosphorus accuracy

Hello,

When I take a reading from my Hanna checker, should I + or - 0.04ppm onto my reading because of the accuracy on the attached, what does the 4% mean?

*** SEE ATTACHMENT BELOW

HANNA CHECKER.jpg

Thanks


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Old 03/19/2018, 07:53 AM   #2
pisanoal
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Not sure exactly what you are after, but "trust" the reading you are seeing. Just know that it could be a little bit to either side of the reading. 0 might not be true 0. 0.04 might be 0, that's why you need to couple observation with testing. If you are getting algae on the front glass every couple days and you are showing 0, its probably not true 0. If you have pale corals and go a week without cleaning the glass, and you have a 0.04, it might actually be closer to 0.


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Old 03/19/2018, 08:19 AM   #3
mcgyvr
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It means you are too smart for their specifications..
Stop paying so much attention...
It can't be both without some unstated stipulations..

Note: some vendors list it as precision too.. And precision is not the same as accuracy..

If your phosphate level is greater than 1ppm its accuracy can exceed the stated -/+ .04ppm if the 4% is really the accuracy..
Or maybe thats what they were trying to say.. Its accurate to .04ppm when levels are below 1ppm and accurate to 4% if greater than 1ppm.
???


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Old 03/19/2018, 10:02 AM   #4
Tripod1404
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You dont add or substrata anything. That just shows the expected error rate of the device. So if you made 100 measurements of a 1ppm standart PO4 sample, 95 (or 95%, depending on the significance threshold they use) of the results you obtained would be in between 1.04 and 0.96 ppm. This means device is not significantly likely to make an error larger than 4%, as long as there are no sample preparation or user errors.



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Old 03/19/2018, 10:20 AM   #5
mcgyvr
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^^yes you don't add or subtract anything..
Ok my "too smart" comment may have been a little off base now that I reread your post..
I thought you caught onto the fact that it can't be -/+.04 and 4%... my bad..


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Old 03/19/2018, 06:35 PM   #6
Dan_P
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Quote:
Originally Posted by fishkeeprian View Post
Hello,

When I take a reading from my Hanna checker, should I + or - 0.04ppm onto my reading because of the accuracy on the attached, what does the 4% mean?

*** SEE ATTACHMENT BELOW

Attachment 388895

Thanks
It is stated as accuracy but the precision I measured for this instrument is close to this value.

For any given reading, you should be aware that the true value will likely be somewhere within the range of +/- 0.04 ppm +/- 4 % of the reading. One important message here is that a reading of 0 ppm may not be zero and a reading of .04 could be zero.

Does that help?


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Old 03/19/2018, 10:11 PM   #7
bertoni
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To simplify, for low range tests, the reading you get should be with about 0.04 ppm of the truth, if everything is working properly.


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