Stephen R Phillips wrote:
> I suggest if you have a high side shunt resistor for measuring current you look at linear tech's line up.  Unfortunately NONE of there stuff is cheap. You stated cheap so you may need to shed the idea of the huge voltage range or measuring everything.  What I suggest is you first make something that works, then find out what you don't need and make it a lot cheaper.  How many units are intended in the final design? 1000's? 

Quantities are probably going to be in the 1000's/year range.  Perhaps 
10K over the life of the device.  I'm at the stage in the design where 
everything is done except the signal conditioning part, and the problem 
is that if you look at the things which are likely to be hooked to this 
device, they are varied and wide.

The shunt part is actually one of the easier parts to deal with - there 
are lot's of options for high side monitoring, like the LT stuff you 
mentioned.   Analog Devices and TI have some as well, along with I 
believe Maxim.

I'm sort of leaning towards simply saying that all of the analog inputs 
are ground referenced, and then providing some different ranges of 
inputs, perhaps jumper selectable.   And then, for those applications 
where I can't do a ground referenced input, do more exotic signal 
conditioning in a separate device (with a separate power supply) - and 
pass the additional cost on to those customers who need this (which are 
common, but perhaps 5-10% of the total customer base).

What I had hoped was for some magic, inexpensive solution where I could 
avoid issues with measuring everything in relation to ground, including 
unexpected ground loops or similar.   So far, it seems like doing this 
is going to be extremely expensive.

-forrest
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