Thanks for the exact document that I was looking for. The tips given for filtering, offset adjustments and temperature compensation are all very good. Will implement them and should be OK for this application which would do with a overall accuracy of 1%.

The AN also highlights the two major pitfalls - response time and ripple. Yes I can make do with a 1 sec response and thus can use an agressive smoothing. Should be fine.

And regarding the Eagle's eye - it is very true that nobody ( maybe except an Eagle ) can spot a 0.1% difference on an analog meter! But the display IS digital and hence the concern.

As Peter said, no analog system can match a properly designed digital system to handle this F-V conversion. True, but my basic query was : given the client's requirement, would not the LM331 be a simple solution ? Appears it is, based on the AN from National.

Thanks

Raghu