I've used the Maxim high-side sensors in a previous design, but in this
case, I have the shunts in the -ve side of the battery - it makes life a
lot easier.

At 05:16 PM 10/22/2002 +0100, you wrote:
>>An option is to use  a rail-to-rail op amp's (running from 5 volts) with
>>gain of 1 on the input to the PIC - this will limit the voltage and protect
>>the PIC. However, if I can avoid this, I'd like to.
>>
>>Comments? Ideas?
>
>Couple of ideas.
>
>1. Check out the devices at LEM
>http://www.lem.com/inet/lem.nsf/$wFSS!ReadForm&Lan=EN
>
>They do a range of hall effect sensors, but you need to be careful, as most
>use +/-15V supplies. They have an internal op amp to give a volts/A output.
>
>2. Check out the current sensors from Maxim. I believe other manufacturers
>may also do these. They have a range designed for the cell phone market, but
>I am sure could be adapted to your use with suitable sense and scaling
>resistors. These are designed as a three terminal device for high side
>current sense, with two terminals across the sense resistor, and the third
>terminal going to earth through a suitable size resistor for the scaling
>factor you want. I have not used them, but believe they convert a voltage
>across the sense resistor into a current through the scaling resistor. By
>setting the scaling resistor to a suitable value you can set the output
>voltage you want. Some of the devices are described as bi-directional, so
>they handle battery charge as well, presumably they output current has an
>offset value to handle this.
>
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Larry Bradley
Orleans (Ottawa), Ontario, CANADA

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