Is one allowed to use a sand timer on Shabbos to help a child space his eating and time his chewing to prevent over stuffing and choking on food.
If yes, is one allowed to use it for a mundane use as well?
A sand timer is an”hour glass” filed with sand and when you turn it over the sand goes from one compartment to another. there is a 30 second timer, minute, 3 minute, 5, 10….
A sand timer is an object that measures time therefore using it on Shabbos is not allowed since we are not allowed to measure things on Shabbos. However if it is being used to help a small child eat, to prevent him from choking this is medida shel mitzvah and permitted. Besides a young child is considered a choleh, and measuring may be done for his needs.
S”A O”C 306-7.