Hi, I'm working on automotive related project where i'm using INA219 IC's to measure currents.
Its all DC only, and measurement is pretty slow. Maybe every 250ms of so. Im using the following setups:
1) External shunt coupled directly to 12V battery's. measures up to 200A with a 75mV shunt (80mV mode)
2) Only voltage measurement on another battery. Vin+ and Vin- are directly connected to each other
3) 0,75mOhm SMD shunt measuring up to 50A connected directly to 12V system of car (40mV mode)
4) 1,5mOhm SMD shunt measuring up to 20A connected directly to 12V system of car but fused (40mV Mode)
I have done a lot to secure my electronics from the surges common in cars. Common surges can be for example 60V for only a few ms, but a load dump of 200V for 400 ms is also possible.
What can i do to protect the Vin+ and Vin- of my INA219's? The datasheet suggest series resistors and zener devices but doesn't describe what is possible without compromising the output.
As described above i will be working with very small signals (0-40mv) to keep dissipation in the shunts low. I'm using kelvin wires and keeping them as short as possible to keep noise to a minimum. Even for my 50A shunt i need the measurement to be accurate down picking up currents as low as 100mA.
Would a 100ohm resistor between shunt and Vin- / Vin+ pin plus a 24V TVS diode to GND work, or would this surely effect the accuracy of the output?
Hope you guys can help!
btw, i'm not looking to change to another IC. I like the INA219 of its I2C output, great library, and low cost.