Hi ALL
I am using an INA219 to monitor a DC load(24V and 10 A).
I am asking, what is the correct value for configuration register and calibration one to measure this load.
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Hi ALL
I am using an INA219 to monitor a DC load(24V and 10 A).
I am asking, what is the correct value for configuration register and calibration one to measure this load.
Hello Hani,
From you calculation I presume you are using PGA = /8 and your max current is ~10A. You can do that. However you should be aware that although your calibrated current resolution or current_LSB is 305uA, you will not actually achieve such resolution as the voltage across the shunt is what is measured and the Vshunt_LSB is ~10uV while your current_LSB*Rshunt = 3.5uV. Another thing to consider is that there is a voltage offset that also heavily contributes to error in the lower current measurements. For a common mode voltage of 12V, this is typically 40uV; however, it can be as high as 200uV if you are using INA219A.
For additional clarity, I am including a picture below of excel calculations, showing what you may expect to see on the lower end of your current measurement range. The first column corresponds to the ideal discrete current values derived from calibration. Column B corresponds to the ideal shunt voltage that corresponds to those measurements. Column C corresponds to the shunt voltage with the offset included. Column D is the INA219 typical shunt voltage LSB. Column E are the corresponding number of codes or count you would expect to see in the Vshunt register. Column F corresponds to the current derived from your measurement. Lastly column G shows the error.
Hello Hani,
In your previous post you said that the device readings floated up to 65A. I do not see how that is possible if you are using a current LSB of 0.001 with PGA=/8 and the 12 bit ADC. Based off of those settings you can read 32.768A (Current_LSB*2^15) at most. Regardless, I presume your register is giving you the max current value. If this is only sometimes then it may be because you are not averaging and may occasionally sample during the high portion of your duty cycle (I presume this is related to your other post here). If you do not apply a PWM and just have a static 0.7A load, does it still look like 1.5A?