>
>2 wrote:
>>
>>>
>>>One other trick to check a transformer is to measure the resistance of the
>>>secondary winding. ...
>>
>>// Bingo. The primary winding R as well as the mains R are also
>>factors.
>
>The *effective* secondary resistance - including the contribution from
>the primary - is the value that should be used in calculations.
>
// True
>If the primary resistance is too low to measure accurately (which it
>should be for the kind of transformers we're interested in!) the total
>effective secondary resistance is roughly double the measured secondary
>resistance.
>
// Agreed. However a low R can be accurately measured with a DMM by
putting 1ADC through the primary and measuring V drop. 1.0mV drop =
1.0m?. The same method is useful for evaluating vacuum relay contact
resistance.
cheers, Ian
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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