Obviously the cheaper the unit you buy the less features it has, then just use the function you want. When I mean cheaper I mean a good brand but their bottom of the range, look around some older LBS see if they still have some old stock left, the newer ones have far too many features & to me the displays are small, you might try posting your question under the other heading below, these tends to cover all those questions you ask.

https://www.bikeforums.net/electroni...hting-gadgets/