+1 for Xikar

I use 12 of them.
Replace the batteries, clean the contacts, and recalibrate every 8-10 months (all at the same time - makes it easier to keep track of maintenance dates).
All show +/- 1% of each other.
Because of the RH in the humidor (64%) I use DeOxIt electronoic contact cleaner/de-oxifier on the battery contacts.
- Without it my battery contacts were showing oxidation in less than 1 year.
- Contact oxidation will affect accuracy.