Preferred database solution for storing sensor data
In general you do not want to normalize the data you are stuffing into whichever NoSQL solution you are using, in other words, you want to leave the redundant information there. Otherwise you should be using a relational database system like MySQL,Postgres,SQLite, or MSSQL (Express edition is free, but has database size limits). If you use any of those systems, reducing redundant information would be beneficial.

Honestly, if you are looking to grab a bunch of sensor data, then display it as a graph at a later point, you might want to look into setting up a box with Elasticsearch + Kibana on it. You can get something up and running in a matter of minutes with VERY minimal amounts of configuration: https://www.elastic.co/products/kibana

When Neo4j calls itself a "graphing database" it is not graphs in the visual sense of the word, it is graphs in the relationship sense: https://en.wikipedia.org/wiki/Graph_database

Hope some of this helps.