I own two. The cheap $14 one and the Bluelab Truncheon. They both accomplish the same thing, only the Truncheon is waterproof and can easily reach inside watering jugs. I've also noticed the Truncheon reads slightly lower than the cheapy pen. I still use both for different things.
Even if it's cheap it will still do the trick. That way it will be much easier to see what the plant needs. You could start with 1.4-1.5 for example and build your way up from there. Once you see the tips of the leaves burning slightly you'll know your plants limits on what it can handle. This way you never feed to much or not enough.
First time I heard that. What are you planning on testing?
Soil mixed with water Then filtered out.