Issue link: https://iconnect007.uberflip.com/i/1526666
78 PCB007 MAGAZINE I SEPTEMBER 2024 you have conducted some type of wet process audit using the worksheet in my last column and now have some idea of where improved process control will improve performance. The Specific Gravity Controller Figure 1 shows level sensors that you can buy from Amazon to make the DIY specific grav- ity sensor seen in Figure 2. You can also buy relays that can be used with these level sensors. Figure 2 shows the calibration/design chart for the SG sensor I illustrated last month 1 . e operating setpoint for SG that Don Ball of Chemcut recommends for cupric chloride or alkaline etchants is indicated by the red star on the chart. Below the chart is the plas- tic calibration rod that needs to be fabricated, threaded, and then to have the center drilled out based on the Figure 2 calibration for oper- ating point and adjustment range. With a set- point of 1.27 SG and a total range of 0.1 SG, the intersection on the chart has a drill depth of 2.30 inches and a nut diameter of 1.55 inches. With 50 full threads for the plastic adjustment Figure 1: Two liquid-level sensors and AC 110V control relays available from Amazon that can be used for the specific gravity sensor, provided the design chart software is modified.