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INA238: error by 0-10A

Zhiwen Zhang
Prodigy 30 points

Part Number: INA238

Tool/software:

for my aplication: maximum expected current= 90A, ADCRange=0,(163.84mV), Rshunt=0.001 Ohm
This is my messure results up to 10A.  It seems that as the current increases, the measurement error becomes larger.

is INA238
0 -2,75
505 524
1010 1052
1515 1579
2019 2106
2322 2425
2524 2633
3028 3164
3533 3688
4030 4218
4540 4746
5040 5273
5550 5800
6050 6328
6560 6858
7065 7382
7570 7915
8080 8445
8590 8973
9090 9500
9560 10027
10000 10555
10500 11085
11000 11618
11500 12150
12000 12680

Why is there such a large error? Can I easily calibrate it with a proportional factor?

2. in Datasheet, to caculate current_LSB, the Maximum Expected Current is in my sitiation 90A? Why is this parameter so important? for exsample, when my Expected Current is 100 A, the Current_LSB will change.
or is Maximum Expected Current  a calculated parameter, according to Rshunt. or it is only a Estimated parameter?


Thanks for reading.
Zhiwen Zhang

  • +1
    TI__Mastermind 35680 points

    Hi,

    The proportionally increasing delta is a typical behavior of gain error, which can be attributed to either or both of the gain errors of shunt resistor and INA238. This error can be calibrated as you mentioned.

    The calculated current LSB based on max current is simply a mathematical scaling factor, it has no effect on the property of INA238. The reason to scale LSB with max current is so that the full output range is utilized. Of course you could use a large LSB for a small max current, and use only a small portion of the output range, losing some resolution.

    Regards

    Guang

  • 0 in reply to Guang Zhou
    Prodigy 30 points

    Thanks for your answer. But when the current is 12A, the error will be 680  mA. Is this also due to gain error?

    2 For every sensor, the calibration is different from eath other( i guess), it means if i want to produce many products, (using many sensor), every sensor should be calibrated? or what are the usual practice?

    Thanks a lot

    Zhiwen