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Original question:

INA226: Need to sense current from 1mA to 1000mA with a resolution of +/-1mA, is the INA226 the best choice?

INA226: Best current sensor for 0-100A range, 26v

Sean Kovacs
Prodigy 140 points
Part Number: INA226
Other Parts Discussed in Thread: INA282, , INA219, INA190, INA186, INA229

Hello TI,

I'm curious as to which of the 100 current sensors you make will be best suited for a 0-100A range with +/-50mA accuracy for both an analog (e.g INA282) and I2C model (e.g INA219, INA226)?

Thoughts are appreciated!

  • 0
    TI__Mastermind 23345 points

    Sean,

    Several of our products will be able to handle this current range, as the amperage is more a limiting function of the shunt itself, rather than the measuring amplifier. I have a few questions to try and help narrow this down a bit:

    - Do you have any bandwidth requirements?

    - Do you need any additional functionalities in the devices (alert pin capabilities, etc.)

    - Is your use case relatively DC, or is this a switching case?

    - Do you need to measure current in both directions, or only one direction?

    - Is your measurement range truly down to 0A, or is some amount of headroom above 0A acceptable? For single supply devices, this forces the use of a bidirectional amplifier, with some amount of reference voltage to keep the amplifier from saturating against the rail

  • 0 in reply to Carolus Andrews
    Prodigy 140 points

    Carolus, Thank you for responding. Understood on the shunt, but wasn't sure if going to small of a shunt (e.g .0005Ohm) would lose granularity in the readings. 

    Since I'm using the sensor for logging and nothing more, bandwidth and alerts or other features aren't a large concern. This will only be in a DC setup and unidirectional. This is for a drone battery monitor. I'm testing a setup with the INA219, but it seems at no load, the voltage values seems not as accurate as when some load is applied. I'm not opposed to analog as well. INA169s are traditionally used in drones, but the accuracy leaves little to desire.

  • 0 in reply to Sean Kovacs
    TI__Mastermind 23345 points

    Sean,

    We routinely see customers design in with shunts numbering in the microohms; these shunts do not necessarily have limiting accuracies, but they do become more challenging to design, and care must be given to layout, manufacturing, and more, as a simple cold solder joint could potentially exhibit more resistance than the shunt itself!

    The reason you are seeing the voltage become more erroneous at low values on your INA219 is due to the offset voltage, which you can learn about here. This will be true of any amplifier, as all amplifiers have some amount of offset, and this remains constant across the full scale range. As the signal magnitude decreases, the ratio of the signal to the offset grows, and therefore the error increases in an inverse relationship. 

    Based on the criterion you've set, you could have a look at the INA190, or its cost optimized version, the INA186. These are precise analog output sensors that also are low power (which I assume is important here being a drone application), as well as enable options for additional potential power savings. On the digital front, I would recommend having a look at the INA229, which is our latest precision digital power monitor. It comes integrated with power, energy and charge functions, and also integrates a temperature sensor.