Sensor
We are now coming to the interesting part as the sensor is probably the most prominent upgrade in this new version, indicated by the "B" in the name. Zowie has with this mouse joined the club of mouse manufacturers who use the best-available gaming sensor, with their implementation of the PixArt 3360. Historically, the first EC mice, released around 2010, used the Avago A3060, a sensor that was already a bit older at the time, before their whole lineup switched to the A3090 with a custom lens (for a lower lift-off distance) in the EC-eVo series. The next step was the implementation of the PixArt 3310 sensor with the EC-A series, and the sensor has now been upgraded to the PixArt 3360.
As the sensor is the best to be had currently, one would expect stellar performance, and the EC-B delivers. Tracking is perfect at up to inhuman speeds, and accuracy is the best you can get.
CPI Accuracy
CPI accuracy is alright - all values are off from the set value, but are off by the same amount. As CPI is a variable of height over surface, even something like the thickness of the mouse feet influences this value. It would be worrisome if some values were higher while other were lower than proclaimed.
With this test, I show how accurately the sensor reports movement at different speeds. You can see me move the mouse at varying speeds from a starting position and back again at a different speed. In the top-right corner is the showpos command in the Source engine. The second row shows the viewing angle, of which my point of reference is mainly the second one, the x-axis angle. With a script, I set my viewing angle to 0 0 0 at the start. After every swipe back to my starting position, I record the deviation from the starting position.
There is obviously some degree of error here due to me performing this test manually because I lack a test bench that limits movement to the x-axis only. I have done this same test with a variety of different mice and sensors, so it's possible to compare. In this test, the angular displacements were 1.66, 2.61, 1.07, 1.82, 3.64, 2.42, 2.57, which is a good result and as expected for a 3360 sensor. In this case, all the values are off by nearly the same amount, which makes me think that it is probably more due to me tilting the mouse because of the shape rather than the mouse itself being off. If you think of the results as groupings on a target range, you have a pretty good grouping here.
Lift off distance
As per usual with Zowie, the lift-off distance (LOD) is very low, below 1.2 mm.