Should I be measuring ppm by 500ppm setting or the 700ppm setting?? And what do I use ec measurement for?? And how old should these girls be before I transplant and feed them?
It shouldn't really matter which setting as long as you convert things right. I've never heard of one having different readings like that though. Maybe post a picture of the pen. Maybe others know, but mine just has one setting to read ppm's. Usually you take a gallon of water, add your nutes, then check the PPM to make sure it isn't too high and will hurt them. If it's high add more water. If low, a little more nutes. I wouldn't feed them for a little while yet. Also when you do you'll want to start with low PPM's otherwise they can burn. General rule of thumb is to start at 1/4 nutrients the first watering, 1/2 strength next, 3/4, full. Personally when I do soil I wait until they're a couple weeks into veg. That also depends on the soil you have though. The soil may already have some in it depending on what you're using.
Sorry, I can't help with that thing. I even tried to check online, but I don't really get it. It was saying you can switch it to measure 500 or 700 PPM solution, but I don't want to switch anything. I just want it to read it. Whatever it is. Weird. You have that much cash to drop on this? I think I bought my PH pen and PPm online for around $30 for the both. Those may be worth every penny, but I have no idea. I'm thrifty. lol.
The 500/700 ppm thing is only a calibration thing. So if you calibration solution says 700 ppm use that if its 500 use that. The conversion is probably not changeable. That's what I think anyways. You can always just go by the ec since it eliminates the whole conversion crap.