Issue link: https://iconnect007.uberflip.com/i/1526666
84 PCB007 MAGAZINE I SEPTEMBER 2024 industries, primarily semiconductor and phar- maceutical, use resistivity instead of con- ductivity. Resistivity is the reciprocal of con- ductivity. e units are MΩ-cm. Here is the conductivity of various waters: • Ultra-pure DI water: 0.01 mS/cm • Good quality distilled water: 1 µS/cm • Excellent quality tap water: 50 µS/cm • 0.05% NaCl: 1 mS/cm • Sea water: 50 mS/cm • 30% H 2 SO 4 (plating): 1 S/cm Measurement of Conductivity ere are two types of conductivity measure- ment: contacting and inductive. e choice of which to use depends on the amount of con- ductivity, the corrosiveness of the liquid, and the amount of suspended solids. Generally, the inductive method is better when the con- ductivity is high, the liquid is corrosive, or sus- pended solids are present. See Reference No. 3 to learn more about the measurement of con- ductivity.. If you purchased a portable conductivity or combination probe 1 , then you can always can- nibalize the probe's electronics. Amphere-hour Totalizer e amphere-hour totalizer is very useful for monitoring electroplating. is is because the components in plating are consumed by the actual current used for the deposition. On newer, more complex plating processes, ana- lytical measurements are still required for some components, using titration and electro- chemical techniques like CVS. A 50 milli-volt or 100 mV current shunt (resis- tor) rated for the maximum current is used in a series with the power supply and the cathode frame. is current is totalized over time as the plating is conducted and then replenishment can be calculated from the reading. Figure 5 shows the schematic for such an amphere-hour totalizer. Its simple design is a Figure 5: Schematic of a conductivity sensor for use with metal or graphite probes and a purchased unit with probe for connection to an Arduino microcomputer board.