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Low and High-Side Battery Current Sensing with OPA241

Jenny Cabascango
Prodigy 5 points


Hi, I want to know how does this circuit work, because I have an application with a battery (12V/4Ah), with a charge controller, and I don't know if I can use this. I changed   resistor RH and RL with 0.1 ohm - 1w.

Thanks for all your support.

Jenny

  • 0
    Guru 21975 points

    Jenny,

    This application circuit shows two ways to measure current in a battery, one measuring on the "high" side of the battery, one on the "low" side. You would only use one of the two circuits in a real application. The selection of which method to use (high or low side measurement) depends on your application needs.

    Each of these circuits measures the voltage drop on a 10 ohm resistor with a difference amplifier configuration having a gain of 10. The lower circuit is a slightly simpler design with four resistors around the op amp to form the gain of 10 difference amplifier. This low-side measurement is easier and does not require highly accurate resistors because the common-mode voltage of the measurement is low. These two blogs provides some background:

    Difference Amplifiers—the need for well-matched resistors

    Making Your Own Difference Amp—sometimes 1% resistors are good enough

    Regards, Bruce.