Electronics > Beginners
Using opamp to sense current over a shunt in both directions ?
Odd:
So I have a 2m \$\Omega\$ shunt on the low side of a design, which is used to sense current up to 40A , (about 100mV or so).
I wish to make it readable by AD (0-5v) - both ways , so that the AD input would look like:
5v = -40A
2.5v= 0A
0v= 40A
I do know it is easy to do with a shunt current sensor amplifier but is it fairly easy using an OPAMP ?
ogden:
Did you try to search internet for "bidirectional current sense application note"? If not - then do it ;) There are notes from TI, maxim and analog devices. Just to name one or two: https://www.analog.com/en/design-center/reference-designs/circuit-collections/bidirectional-current-sense-circuit-with-separate-charge-discharge-output.html
https://www.analog.com/media/en/technical-documentation/application-notes/an105fa.pdf
rstofer:
Search "high side current sense amplifier" There are many and some are bidirectional.
thm_w:
This is the sort of thing you are looking for:
http://www.ti.com/tool/CIRCUIT060007
http://www.cafelogic.com/2010/sensing-bidirectional-current-with-a-single-supply-op-amp/
But most likely there is a better solution in the appnote ogden linked, that would give you better precision. eg an off the shelf high side monitor IC. With less hassle and no caveats like needing matched high precision resistors.
What would help is to post some idea of accuracy and bandwidth requirements.
Renate:
I've used the TI INA219 http://www.ti.com/product/INA219
It's a 12 bit high-side I2C voltage and current monitor.
Did you really want an analog voltage?
TI makes the same thing with only analog output, INA169 http://www.ti.com/product/INA169
Looking through all the variants, I think that I'll use the INA226 http://www.ti.com/product/INA226 in the future.
It's got 16 bits and less offset (but a different package).
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