You have to be physically close to a person to sense Dark Side.
Jedi certainly recognized Dooku as a Dark Side user when they met him on Geonosis. We don't have enough information, but looks like Dooku avoided meeting Jedi since he left the Order and before that encounter. Of course, if someone was very close to person, he could fill Force shift even from affair, but Jedi Order in last days of Republic shunned attachments so Dooku (and other Jedi) didn't have really close friends that could sense what is in their souls even when they are not physically present. Exception could be Yoda and maybe Mace Windu, but this is not elaborated either in Canon or Legends.
As for recognizing someone being a Sith, Force simply doesn't work that way :) Sith were organization with certain traditions and beliefs, but that is about it . Jedi did guess that Dooku is probably a Sith, but they didn't know that he is Tyranus (unit late in the war) and that Tyranus is actually Darth Tyranus.