conductivity tester, handheld device provides a qualitative visual indicator of the conductivity of different solutions, acids or salts, Two brass probes can be touched to a solid substance, or immersed in a liquid, to show conductivity on green LEDs
VWR* Conductivity Meter Atc Hydroponics The P772 is a wide-range, pocket-sized conductivity meter perfect for use in field environments. With 10 uS/cm resolution and +/-2% FS accuracy, ATC adjusts for changes in conductivity due to temperature.