How do I learn RPL and solve this problem with it?

09262017, 12:06 PM
Post: #26




RE: How do I learn RPL and solve this problem with it?
(09262017 01:02 AM)brickviking Wrote: I'm no good at the mathematics behind all this, I've been a bit lost. However, I realised that there's also a realworld value of each resistor, not just a theoretic L<R<U where L and U are the lower/upper 5% bounds. As soon as you add a resistor which ALSO has that same 5% tolerance, you have to hope that for an exact match, your chosen resistors aren't both at the lower edges of their tolerance bands (or higher edges) affecting how close their real (not nominal) value will be to the required theoretic value. Will the two resistors that are low still fall within 5% of the combined value? Ditto for two high resistors in parallel or series. This is an important point. Also, standard 5% resistors have greater thermal variation than 1% resistors, so I don't think it's realistic to try to get a match within 1% of the desired value. IMHO a better definition of the problem is to sort the viable combinations by closeness to the desired value and pick the best one. John 

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