The Divergence Meter
The Divergence Meter is a device brought back from 2036 by Suzuha, invented by the future Okabe for his own personal use.
It is a modified Nixie tube clock that uses an unknown method to determine the "Divergence Value" of the current world line in relation to the absolute world line of 0%.
The Divergence Meter is used to calculate what Attractor Field the universe is currently in. Throughout much of the storyline, Okabe tries to break the 1% barrier (create a world timeline change so significant as to raise the first, leftmost Nixie tube value from a 0 to a 1) to escape from the Alpha range, using the meter as a reference each time.
Okabe is the only one who can effectively use the meter, as his Reading Steiner allows him to remember what its previous values were across world line changes. To anyone else, the numbers always follow the same pattern inside his or her corresponding world line.
Even Suzuha, who herself had time-traveled to bring the future device to present-time Okabe, couldn't tell if it had changed. According to Tennouji's recollections of her near the end of episode 16: in her final year of life, she was always wondering if she was able to successfully alter its values because of her actions:
- Suzu-san had this. Do you know what the number means? She was always looking at it, from her hospital bed. "Is this the number before it changes or after? Did I manage to change it?" Whatever it was, it bothered her to the end. — Yuugo Tennouji
In the future time of its first invention, it was originally in Okabe's possession; when he died, it was passed on to Daru, and in turn was passed on to Suzuha. Suzuha then traveled back in time to give it to Okabe, completing the cycle and having the Divergence Meter's existence contribute to its own invention without realizing it.
It has some limitations in that it cannot display certain values; this is shown in the Omega Attractor Field, in which the first digit cannot be displayed due to the divergence being negative.