Electronic Manufacturing, electronics podcast, MacroFab, macrofab engineering podcast, Screen Printer

MEP EP#240: Disturbed Solder Accuracy

Podcast Notes


  • Got a fully automatic screen printer!
    • ESE US-2000X
    • Potentially lower our minimal paste size
  • Twitch Live Stream podcasts?
  • Amazon multimeter probes


  • High voltage low current measurement
    • Don’t want to break the connection so a traditional ammeter isn’t going to work
    • Sticking with the read both sides of a resistor method
    • Caddock 1776-C681 high voltage high resistance high tolerance divider
      • 1/100 so 0 to 500v becomes 0 to 5v
    • ADC – MCP3551-E/SN
      • 22 bit
      • SPI
      • 2.4 meg ohm input impedance
    • Ideally the voltage divider has a “gain” of 0.01 but if the ADC is directly attached to the divider the gain is around 0.0096
      • Full scale would be 4.8V instead of 5V
    • Solution: add a buffer
    • AD8244BRMZ
      • Quad buffer 
      • Typical offset voltage of 100uV
      • Gain error of 0.03% max on +/-15v rails 
      • 10T ohm and 4pf input resistance/capacitance – 10^12
      • Gain error is now 0.009999999901 – Close enough

Special thanks to whixr over at Tymkrs for the intro and outro!