Qn: About digital thermometer

[Wzierbovsky]

I picked up this digital thermometer for $10 at Lam Soon LFS a week ago, and have a query about it. I've seen it for sale at quite a few places, so thought others here may know more about it.



Specifically, are there any settings for this device?

Also, what is the FSW button for?

Maybe my unit is faulty, but the thermometer occasionally gives wildly fluctuating readings. Within the space of 15 seconds, it has jumped from 29.5 to 33 then back to 30.5 degrees before even though nothing is done to the aquarium. My thermometer is situated towards the back of the tank and some distance away from the filter pump.

[michael lai]

I think the button is for the light. But FSW stand for what I don't know.