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38 SMT007 MAGAZINE I AUGUST 2023 Data Acquisition e variety of data acquisition devices (DAQ) have increased significantly over the past 20 years. As seen in Figure 3, industrial devices for four analog channels start at a mere $85 and can range up to many thousands of dollars for six-digit multimeters that do 50K readings a second for many hundreds of chan- nels. Multiple protocols are available for inter- connection. e popular programmable logic control- lers (PLCs) also have analog and digital inputs and start at very reasonable prices, like I men- tioned for the industrial devices. For data analysis and signal conditioning, a personal computer can be used, though a microcomputer— such as the Raspberry Pi or Arduino—is much lower in cost and can be suitably protected for use in manufacturing (Figure 4). e Raspberry Pi 4 is my personal choice because of its popularity, flexibility, operating system, connectivity (general purpose inputs ough sensors, which are important for PCB fabrication and assembly, are harder to find, temperature sensing is by far the most common, followed by liquid level, and water conductivity. For chemical processes, Table 1 lists the most frequently used electrochem- ical sensors 6 . My favorite, though seldom used, is specific gravity. I favor it because most chemical processes in fabrication or assembly are aqueous. Changes in chemical concentrations can easily be detected by spe- cific gravity changes and then measured with a hydrometer. In my career, I have focused on four groups of sensors for analytic data 4,5 : • Specific gravity • Spectrometers: e LEGO spectrophoto- meter is quite easy to build • Ampere-hour for plating: An AH totalizer component can cost less than $5 • Electrochemical sensors: Cyclic volta- metric stripping for plating additives Figure 2: Sensors for electronics manufacturing: a) Lot code readers; b) The LEGO spectrophotometer; c) Ampere-hour meter; d) Various object sensors; e) Non-contact proximity sensors; f) In-line confocal microscopy serves as 3D measurement sensors for fine-line HDI geometries. (Source: LMI Tech 6 )