Quote:
Originally Posted by Cr8havoc
Thank you, I updated my checklist. I also read Shell's Guide to DEF and it seems tolerance is +/- 1.5% of 32.5. If that is the case then it is considered out of spec at 32.0105 or less and 32.9875 or mode. Also thanks to all for the DEF specific refractometer, easy to use. The DEF reader with 3 floating discs was not even close and read good DEF as being BAD.
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Randall, a couple of points:
1) If 32.5% is ideal and the tolerance is plus or minus 1.5%, I don't believe that means 1.5% of 32.5%. I believe it means out of tolerance is anything below 32.5% minus 1.5%= 31% or anything above 32.5% plus 1.5% = 34%. In other words, the acceptable range is 31% to 34%. Other sources indicate a tolerance of plus or minus 2.5%, which would make the acceptable range 30% to 35%.
2) Regarding the DEF testers with the three floating discs, it's easy to become confused about how to read one of those testers. I’ll attempt to explain with some photos.
The first photo shows a floating bulb tester packaged for sale. That particular one is sold under the “Performance Tool” brand name, but the exact same tester is sold under the “Thexton” brand name as well.
The second photo is the same as the first except I’ve added some annotation. Specifically, what I’ve labeled “Fill Line” is the line to which the tester should be filled with DEF. In actual use, you’ll usually suck in more than that, so it’s important to squirt some back into the tank until the level of DEF in the glass tube is at the fill line. At that point you elevate the black hose to hold the level constant.
Also identified in the second photo are the three bulbs – a white, a green and a blue. The white bulb is barely visible in that photo.
The third photo shows the back side of the tester, and you can clearly see all three bulbs in that shot.
The fourth photo provides a close-up view of the test instructions printed on the glass tube. Unfortunately, the instructions are not especially well written and and this is where confusion can set in.
The procedure is actually dead simple. You fill the glass tube to the Fill Line with DEF from your tank, wait a few seconds, and see how many bulbs are floating. If the number is two bulbs, the tester is indicating your DEF is within spec. If the number is zero, one or three bulbs, the tester is indicating your DEF is out of spec and needs to be replaced.
Where users get confused is comparing the position of one of the floating bulbs to the lines of percentages under the Fill Line and assuming that a disc floating over one of those lines is indicative of that particular percentage.
That isn’t the way this particular tester works. As explained above, it’s as simple as counting the number of bulbs that are floating. It two bulbs are floating the tester is saying all is well. If anything other than two bulbs are floating, the tester is saying the DEF is bad.
Regarding the accuracy of these floating bulb testers versus a refractometer, I have both but haven’t taken the time to run a comparison test. I’ll do that soon and report what I learn.
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