I’m finding it very frustrating to calibrate my device.
What digital thermometer do you have? Every home thermometer is far less accurate than the temperature control circuitry in you unit. Most home thermometers especially the bi metal ones are notoriously inaccurate. One way to check your thermometer is to make an ice bath with water. This should register almost 32°F or 0°C repeat with boiling water and you should see 212°F or 100°C. If you dont it is a good indicator your thermometer is off. Does the circulator reach and maintain the value you set?
My experience with most home thermometers is the same as @john.jcp but I’m personally troubled by the disparity between the set temperature and the temperature measured by the unit itself. These should ultimately agree (+/- 0.1C). The Anova Precision cooker will “throttle back” as it approaches the set temperature. In my experience it rarely overshoots by more than 0.1C. In effect it should ‘creep up’ on the set temperature. Once a pouch of food is placed in the water it will naturally drop a bit (depending upon the volume of water in the cooker reservoir and the temperature of the food pouch itself.). It will then creep back up to the set temperature. In my experience, once up to temperature, adding the food requires about 15 minutes to fully stabilize. After that the control is pretty much rock solid.