Jump to content
43oh

Current Measurement Circuit


Recommended Posts

Hi Guys,

 

I am trying to build a circuit that the MCU can measurement the current consumption of the circuit. I have read a few things and decided to go with the "low side" measurement.

Incidentally I have some BB INA's laying around from my previous project, so I use it as the amplifier of choice.

I am confused that which "Ground" should I connect the amplifier ref. and Voltage ref GND to - the ground of the load (virtual ground) or the ground of the system (0V)?

Most importantly, will the circuit work?

I am more a digital guy than analog - help appreciated. Thank you!

post-35770-0-71809000-1391194579_thumb.png

Link to post
Share on other sites

I think you can remove virtual ground entirely.  Since you are using an IA, which does a great job of rejecting common mode voltage, you are able to use a small value resistor value for your current measurement and still achieve good accuracy. This will reduce the need for a high wattage resistor (assuming your load is high current). You should be able to tie the ref pin on the IA directly to ground (0v).

 

Also since you are running a +5v supply please note that your output swing will be limited to ground+1.4V and Vcc-1.4V worst case (typical is .8v to .9v).

 

TI has some great app notes on instrumentation amplifiers so you may want to search their site. 

Link to post
Share on other sites

Oh, I almost forgot the INA128 could not produce rail-to-rail outputs and I will probably lose the low current measurements.

After reading some application notes, I guess I should use some proper current shunt amplifiers. INA214 looks good to me...

Thanks a lot!

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...