XPost: sci.electronics.design   
      
   On Sat, 25 Aug 2018 08:32:50 +0100, Terry Pinnell   
    wrote:   
      
   >A side issue arose has me puzzled. I found about 1V DC across a twisted   
   >pair cable, disconnected at both ends, buried in several places. How   
   >does that come about? Even the short section I've cut out, with gaffer   
   >tape around connector blocks, has about 0.5V DC.   
      
   DC voltages below 1 V could indicate some electrochemical pair between   
   dissimilar metals, such as the multimeter probes and the actual wire.   
   If the conductors were supposed to be separated, a well conducting   
   fluid could cause such phenomenon.   
      
   Did the multimeter show anything on the AC range ? Some multimeters   
   show some DC reading even with a symmetric AC voltage.  Asymmetric AC   
   (even harmonics) could also cause a DC indication.   
      
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