I use 1 to test soil fertility and ph and if I put it in my liquid fert it pings max so deff soil only. Mine also likes moist soil for it to provide me with accurate results.
If you want to test liquid ph and ppm on all your nutes id buy a good meter or go the cheap route and goto a fish or aquarium store or petco and buy the kit with the vial and dropper for 5-10$ ea.
If you want to test liquid ph and ppm on all your nutes id buy a good meter or go the cheap route and goto a fish or aquarium store or petco and buy the kit with the vial and dropper for 5-10$ ea.