Sorry about the BBS. It malfunctioned as computers some times do. I couldn't figure out why I wasn't getting any questions.
When I tried organics (bat shit) I had a hard time measuring PPM even with a TDS meter until I read that it is normal to get a false reading when using organics.
Sorry but their is just no cheap way around not using a TDS meter.
pH you can use cheap test tape for a reading but for PPM the only way to measure is by adding one gallon at a time to what it says on the bottle to add to give you a correct PPM. Usually 1/2 to 1 1/2 teaspoon of
nutrient solution per gallon of water, depending on the age of your plants.
A multi-test meter won't work because it relies on an outside electrical source to get a reading and a TDS meter has it's own battery to send an electric current across it's electrodes to measure parts per million in your solution.
Haven't tried areoponics yet but is on my list of things to try.
Ron