The other one you reccomended also claims to be +\-4. I understand that it's hobby grade but a low range meter doesn't help me if I can't tell which direction my readings are going in. Thanks for your thoughts.
Yeah but it more stable in readings. This seems to what is bothering you.
"Hi, sorry for the delay in response! I've been traveling for trade shows the last two weeks, and I didn't have the email notification for this forum set up correctly.
The HI 93713 and the HI 713 use the same method and reagents to perform the test. The biggest difference between the two is the light source. The HI 93713 uses a tungsten lamp, while the HI 713 uses an LED. I have not seen any "official" or published work examining any advantage of one over the other. However, on another thread on this site, someone compared tests on them, and found that the HI 93713 gave more precise, but not more accurate, test results than the HI 713.
As a side note to this, we are currently in the process of discontinuing the entire HI 93xxx photometer series. It is my understand that we will have two photometer series: the Checker HC series, and the HI 96XXX series.
The HI 96XXX photometers offer a great many more features, such as Good Laboratory Practices, CAL-CHECK validation and calibration, water resistant case, etc... There will be a HI 96713 (low range phosphate), but it is not available at this time."
She is wrong about the lamp. But it been tested on the forum and this is correct.
http://www.reefcentral.net/forums/showthread.php?p=18162400
Thanks! Jessica