Description

MEP EP#240: Disturbed Solder Accuracy

Parker

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

Stephen

• 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