best way to measure voltage/current with PIC??

[mcafzap]

For measuring current another device suggests itself to me, though I regret I can't find its number at the moment. It is/was a device made by http://www.zetex.com and had a zero ohm shunt within the package and found the current by using built in magnetic sensing. This has the advantage that the measured current is completely isolated.

In any case, even if it's no longer made there are several more conventional current sensors on this site.

All you atheists have a happy midwinter feast.


Found at

[buckeyes1997]

hey neil
i ordered a few samples of those hall effect sensors as well. they have confirmed that they are shipping them now. ill be interested to see how that can be used. i still like the idea of using an external shunt and the amp.

even with the shunt in the negative rail at 0v there will be some voltage drop across the shunt and you are saying i could simply use an op-amp in non-inverting mode to add gain to get the output in the range the ADC can handle. This idea requires few parts and would be very simple to build. i will continute proceeding in that direction for now. i need to learn more about how to make the ADC work using the CCS.

i will post some schematics once i figure out how im going to lay it all out.

thanks and happy holidays to everyone

[Sandman]

The MAX472 chip is good and works rather well. I have encountered some problems to make it work as specified thou. The output voltage has been linear, but does not follow the formula specified in the datasheet. But, I still use it and it could just have been some adjustments errors so I don�t want to advise not to use it.
I could give an alternative thou. Texas Instrument has just come out with a new current sense amplifier, INA193. Have not tested it, but it looks nice and works for current measuring in supply lines down to -16 V and up to 80V. The circuit layout is very simple, like the MAX472 and actually requires one resistor less. The three available gain scales so there should be one for your application.
Another difference is that the INA19X is limited by the edge of the supply voltage and MAX472 saturates already at ~1.2 V below Vdd which could limit the accuracy of your measurements (depending on the reference voltage).
You can follow the link bellow (datasheet and free samples) if you are interested:
http://focus.ti.com/docs/prod/folders/print/ina193.html
As I mentioned, I have never tried it so if you do, it would be nice to hear if it was worth the effort.
Good Luck!