[INA169] Using INA169 to measure 200A

Nuno Dias

Other Parts Discussed in Thread: INA169

Dear Sir

I would like to measure current with INA169 from my system with the following specifications: Imax = 200A; Vmax = 55V. The desired full-scale output voltage is 5V (ADC input). I'm using a 0.25mOhm shunt resistor (two 0.5mOhm resistors in parallel) and a 100kOhm RL resistor.

When i had make my first tests i notice that the output voltage is around 11V when I have a input current is only 3A.

Have any solution could to solve my problem?

Thanks

======================================================
I'm using the following components:
* INA169
* RS: 2 x 0.5mOhm (10W, 1%)
* RL: 100kOhm (250mW, 0.1%)
* CL: 0.1uF (output filter)

over 10 years ago

0 Jason Bridgmon over 10 years ago

TI__Genius 14825 points

Nuno,

I expect that your equivalent shunt resistance is larger than you think because of solder and possibly layout. When you debug, please put 3A through the shunt as you said and then measure the voltage with a good meter at or even physically on the pins of the INA169. My prediction is that you will find the voltage there equivalent to your output/100.

Assuming that this is the case, your first option to fix it is to use a bigger shunt resistor and smaller RL, which is basically producing a bigger input signal with less gain. Make sure your resistor can handle the power dissipation.

Let us know the results of your debug effort, and perhaps provide the layout of the shunt resistor and INA169 in your board.

0 Nuno Dias over 10 years ago in reply to Jason Bridgmon

Prodigy 190 points

Now, I noticed a problem. When i did the pcb to test this sensor, i forgot to mirror the pcb layer.
So I have the sensor pins swapped.

Thanks for the promptness of the response. Later, I will give news.

0 Nuno Dias over 10 years ago in reply to Nuno Dias

Prodigy 190 points

After changing the sensor pins, everything seems to be OK .
: )

0 Jason Bridgmon over 10 years ago in reply to Nuno Dias

TI__Genius 14825 points

Glad your issue is resolved!

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[INA169] Using INA169 to measure 200A