The Thaumometer is the first tool you need to start your adventures in Thaumcraft 4 that can be created anywhere(if you have NEI. Otherwise, as soon as you have made your Thaumonomicon).
The Thaumometer allows you to scan things (blocks, items, mobs, nodes, etc.) to identify their aspects, and collect Research Points. Looking through them also allows you to see aura nodes. Once something is scanned, viewing it through the Thaumometer will display not only its aspects, but its in-game name, including the type and strength of nodes.
Thaumonomicon Entry Edit
This thaumometer is one of the most useful and important tools in a thaumaturgists arsenal, second only to the wand.
Firstly it allows you to scan objects, creatures or mystical phenomena and determine their magical make-up. You simply need to hold the right mouse button and wait.
Secondly it makes discovering nodes easier, as they become clearly visible if viewed through the Thaumometer's lens - even through solid objects!
Any aspects of shards can be used.
Scanning objects takes a second or two; scanning mobs is faster, but still may be somewhat hazardous. Note that some odd things can be scanned, including constructs and projectiles. Most scannable things will give research points equal to their aspects, and some will unlock research topics. Aura nodes will give about 1/10th the node's strength in each of its aspects. Note that there are soft and hard caps for the amount of research points you can accumulate. These are fairly high, but if you are getting fewer points than expected, you may be running into those caps. In this case, it's time to use some of the points up by doing research, and/or combining primal points into compounds at the research table.
You will only be successful in this scan if you have already discovered the aspects involved, or at least the component aspects, and you can only scan each item once.
The Thaumometer can also help you detect aura nodes, turning them from tiny invisible balls in the middle of nowhere to bright, glowing spheres which can be tapped for their energies. Later, the Goggles of Revealing will provide continuous "auravision", but the Goggles can't give you research points, nor identify things by name.