i thought about purchasing one of those types. but the thing is, what if you have more than one res to test? like i have a flowering res and a seperate veg system. youd have to disconnect everything out of ur res and move it over to the next one just to test, kinda a hassel. for the same price u can get that milwaukee one that is portable and is a trusted name brand. i also really never have to use solution to calibrate mine, if i wanna know its on mark i just put it in some reg water and make sure it goes to the right ph, ppm etc. the only thing is it doesnt have a temp guage. but u can use any thermometer for that.