At 02:33 PM 3/31/2004 +0200, you wrote:
>Hi
>
>I need to measure the following with a pic-micro controller:
>
>   - DC voltage range from 0Vdc to 230Vdc with at least 1V intervals.
>
>   - AC voltage range from 0Vac to 440Vrms with at least 1V intervals.
>
>
>
>I need complete isolation between the high voltage section and the micro
>controller. I have an idea for AC, but the how do I solate the DC?


One method is to use a linear optoisolator such as the Infineon IL300.
You'll need power on the high voltage side, and the unadjusted
accuracy is quite poor, so almost surely you'll need to calibrate
each unit.

If cost is no object, drop an isolation amplifier in there. Some
supply their own galvanically isolated power to the high voltage side.
Check out AD and BB (now TI). There's no free lunch, you either have
to provide power on both sides or part with a fair bit of scratch.

Both the above methods provide a lot of bandwidth, in the kHz range
or higher with little trouble.

Or just put a microcontroller with ADC on the hot side with an isolated
digital serial link. This method probably gives you the most bang for
the Rand, but the bandwidth may be limited by the isolated serial
interface.

Best regfards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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