I have no experience with the one you posted so won't comment. There should be detailed instructions on how to calibrate with whatever meter you use and they usually recommend calibrating once a month or so.
You purchase calibration solution at any hydro shop. The solution is known to have a specific PPM. You put the meter in the calibration solution and if the meter reads the same as the PPM of the calibration solution - you are calibrated. If they don't match, then you'll have to turn a screw or dial until the meter reflects the PPM of the calibration solution.
If you really want to test the accuracy, get two different PPM calibration solutions. Calibrate your meter to one and then test it in the other. For example: calibrate to a 1200 PPM solution and then test it in a 400 PPM solution.
Note that you should do the same thing with your pH meter (calibrate with solution).
I went through a couple of cheaper meters but had trouble calibrating them and they usually didn't read correctly when i experimented with two different calibration solutions. I ended up getting this one:
HANNA instruments® :: Portable
and have no regrets. easy to test calibration, calibrate, use, and clean. But it is expensive and you'll need to buy the Cal-check solution and storage solution along with calibration solutions. One cool thing is the testing probe is replaceable in case it breaks or no longer holds calibration.
But the cheaper ones do work well and many, many people have had successful grows using them.
anyway - i think i rambled enough for now....
