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Part Number: INA210
Our application requirement is as below and we are in need of a Current Sense Signal Conditioning/Amplifier for this.
Current Range - 1mA to 30A
Resolution - 1mA
We are using low side current sense for this as high side will lead to high common mode voltage. We plan to use a current sense resistor of 25mOhm to counter lowest current measurement. Doing the math for 1mA to 30A will lead to a voltage drop of 25uV to 750mV across the sense resistor.
1. Can you suggest a suitable Current Sense amplifier/conditioning to measure this differential voltage across the resistor?
2. Also, even with a highly precision Opamp, offset voltage tends to be in order of tens of uV. Our lowest measurement might me well below this offset voltage. Will this impact our application considering we will be calibrating this system before its use to nullify the offset error?
3. Are instrumentation amplifiers are required for this application or can this be achieved using a precision Current Sense?
I think you might be able to adapt the TI design TIPD129 (http://www.ti.com/tool/TIPD129) to your application. Will this work for you?
Mitch M, TI Sensing Products Applications Support
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In reply to Mitch M:
Thanks for your feedback.
This reference design uses OPA320 precision opamp with a low noise and low offset voltage. One additional point to note is the use of a negative rail to not saturate low current outputs. But with this design, current is not measured deferentially. The path from Current shunt ground to opamp ground is long and any parasitic will add additional resistance and its affect on higher currents is even worse.
Also, this additional parasitic resistance depends on temperature because of which even if system is calibrated with this parasitic is mind, its performance will become temperature dependent.
With this in mind, do you still suggest to use this Opamp or use any differential Current Sense?
In reply to mithun swamy:
Hello Mithun, I see what you are saying. We do have some unity gain Current Shunt Monitors, the INA138, INA139, INA168, and INA169. Also, you may want to look into the INA225, which has a programmable gain that can be used with a microcontroller to change the gain dynamically. If none of these work for you to get the resolution you need, then a discrete solution may be best. If that is the case, let me know and I can move this conversation to the Precision Amplifiers forum so that they can help you find what works for you.
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