Measuring current

aeklo

I am thinking of using a shunt for measuring loads up to +/-20A (boat battery), and feed this to the BS2.
The shunt gives me a voltage drop of approx. 50mV, which is quite small...

I guess I should use a dedicated A/D-converter for this, but do I need an OPAmp circuit, and in case, are there any pitfalls as the circuit must be powered by the same battery?

Maybe there are cheap dedicated chips for this that I might have overlooked? (cost is a factor)

Thanks!

/Anders

sam_sam_sam

aeklo

You might take at this post this might help you out

Look at the bottom half of the page at

Increasing the Resolution

http://forums.parallax.com/showthread.php?p=622885

I hope this help you out with what you want to do

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
··Thanks for any··that you may have and all of your time finding them





Sam

Post Edited (sam_sam_sam) : 1/9/2007 2:00:19 PM GMT

Tracy Allen

The circuit will need to measure the voltage across the shunt only, not voltage drops in the wiring and connections. If the ground connection for the Stamp can be right on one of the Shunt reference terminals, then a single ended 0p-amp amplifier will work. However, if the ground for the stamp will be elsewhere, right to the battery (-) terminal for example, then the amplifier will have to be a differential configuration. That is not much more complicated.

The shunt could be placed on either the low side, connected to the (-) battery terminal or on the high side, connected to the (+) battery terminal. If it is on the high side, there are some very nice current monitoring ics available. For example, the MAX472 would convert the shunt voltage into a current that your Stamp could read using the RCTIME command. Then you wouldn't necessarily need an A/D converter. Here is a reference for that:

emesys.com/BS2rct.htm#B_current

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tracy Allen
www.emesystems.com