How often does loggers upload measurement data to the system?

It depends on the logger type and if the logger is connected to power. Generally CO 03.01/13.01 and CO 03.02/13.02 loggers are used for warehouse monitoring. These loggers uploads measurement data every 10 minutes.

CO 21.01 logger, that are used to monitor stand alone fridges for example, uploads data every 10 minutes if the device is connected to power. If it is not connected to power and runs in Power Saving Mode, it uploads data every 24 hours until the battery level is around 35% (up to 180 days). Then the logger starts to upload data every 48 hours until the battery level is around 5%. (up to 145 days). The logger then uploads data every 96 hours until the battery is empty. Overall, CO 21.01 could, in theory operate up to one year on one battery charge. Cellular signal quality and frequent excursion will effect the battery endurance. 

What is entity?

The measurement data can be organized in a hierarchy and categorized according to collection. Each point in the data hierarchy tree is called Entity. 

What is a root-collection?

Root-collection is the first Entity in the Entity tree. More than one Root-collection can be created in each customer account. Root-collection can be used to create two separate  entity trees in the same customer account

What is a collection and sub-collection?

Root-Collection can have collection(s) under it and sub-collection(S). The collection structure can be used to create a geographical structure around the measurement data for example: 

Do I need to create a complex entity tree to represent sites that I want to monitor?

No, the entity tree can be simple as a group collection. Asset directly under the root collection or skip the root-collection and create asset at the top of the entity tree.