English ESP32 Projects

Things That I Learned From Designing Current Sensor for Ultra-Low Power Device

  • Use Kelvin Connection, this eliminates stray voltage from current-carrying wires. You want to only measure the voltage drop across the shunt resistor.
  • Select your shunt resistor which suitable for your drop voltage requirement. If you’re not okay with 1V voltage drop, then don’t measure 1A with 1Ohm shunt resistor.
  • If you use Op-Amp for amplification, consider its input bias current a.k.a input impedance. Too high input bias current will mess up your measurement especially when you’re trying to work in micro-ampere current.
  • Select an adequate ADC, either it’s 10, 12, 16, or even 24-bit, it’s purely dependent on your resolution requirement. Don’t forget that ADCs sometimes incorporate internal PGA, so consider the input bias current as well.
  • Also, if your ADC requires external voltage ref, choosing an accurate voltage ref will improve your reading accuracy. For me, it is 0.1%
  • Breadboard for prototyping measurement project SUCKS!
  • If you want to auto-range, you will need MOSFETs. P-Channel for High-Side measurement, N-Channel for Low-Side. Each has its pros and cons.
  • You are designing an a.n.a.l.o.g circuitry, so don’t treat this like an Arduino project.

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