Yes, you can take digital thermometers with you, they are not restricted but you can only take a single mercury thermometer.
A mercury thermometer must be carried in checked-in luggage only and must be in a protective case
Mercury is a poison and if taken on board a plane present as a significant risk to passengers and crew.
You will be asked to relinquish all dangerous or prohibited items found in your carry-on luggage. If you refuse:
We x-ray bags going on planes to make sure there is nothing dangerous in them. If something comes up on the x-ray that needs checking, the bag will be opened, searched and any dangerous or prohibited item will be removed.