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* Visual Scientifics Photogate Sensor, Four Modes: Gate, Pulse, Pendulum, Frequency, also Works with VISUAL SCIENTIFICS and numerous physical science systems, This kit contains: 2 Photogates, 2Connecting wires, Main photogate hub and control, Wall charger