It is always a bit tricky to state an accuracy figure, since it depends on what the sensor is connected to and how it has been calibrated.
Assuming you are using DVP-BTA connected to a LabPro or LabQuest, the first number to look at is resolution, which is the smallest increment in voltage that can be measured. For DVP-BTA, this is 0.003 volts. The accuracy depends on how the sensor was calibrated and, to some small extent, the LabPro used.
As part of our manufacturing process, the DVP-BTAs are made with precision resistors and instrumentation amplifiers, so they are quite standardized and checked against a known set of voltages. If the voltage is off by 0.1 volts or more, it is rejected. There is no calibration done because this particular sensor does not have a way to "store" the calibration. (Most of our sensors do have on-sensor storage of calibration).
You can calibrate the sensor, and save the calibration on your computer or LabQuest to improve the accuracy. Just do a standard calibration two-point calibration using shorted leads as 0 volts and a known voltage (measured with a good voltmeter) as another.
As shipped, with no local calibration, the accuracy is something like 0.1 volts, but by calibrating, you can make the accuracy very close to 0.01 volts.