All chakra is detectable,but knowing who's chakra it is and what Clan it belongs recurs a sensor to be familiar with it. Sines theirs only one Living Senju in Tsunade,theirs not enough people to get a cross sample, the same goes for Uchiha. Sines the Uchiha Massacre how many of Naruto generation that are sensors has ever meet a Senju or Uchiha.
