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Testing the Accuracy of Pen Tablets


MovAlyzeR® movement analysis software enables users to estimate the accuracy of a pen tablet. Pen tablets can be evaluated mainly by spatial and temporal errors. A brief overview of what is tested is below, followed by the test procedure. Links to actual accuracy tests performed on Wacom pen tablets are available at the end of this discussion.


  • Estimation of the sampling rate (should be 75-200 Hz)
  • Consistency of sampling frequency (there should be no missing or double samples)
  • Simultaneous sampling of x and y (ideally, x and y should be sampled simultaneouly)
  • Accuracy (ideally < 0.02 cm)
  • Resolution (typically 0.001 cm)


Spatial Errors: Quantization error due to the finite resolution of the digitizer. This error occurs as a result of electric noise and mechanical imperfections. The RMS of this curve is used to estimate the spatial accuracy. As a rule of thumb, if the coordinate RMS error exceeds 3 resolution units, improving resolution will not improve the coordinate RMS error.

Temporal Errors: Temporal errors consist of missing or extra samples and frequency peaks in the frequency spectrum. As a rule of thumb, there should be no missing or extra samples and no frequency peaks in the frequency spectrum. (Frequency peaks can only be visually derived from the chart of the acceleration spectrum).


The test is intentionally simple such that it can be conducted by anyone. Perform the test at least two times and use the best results.

Ensure that you have the most recent pen tablet driver installed. In MovAlyzeR®, go to the Device Setup Wizard to acquire the tablet settings. Create a new experiment, which will inherit the settings acquired from the Device Setup Wizard. Add a group, subject, and a default condition with the default number of trial replications: 2.


1. Place a non-conducting ruler on the pen tablet surface at a 45-degree angle.

2. Run the experiment that was setup above.

3. When the trial begins, draw a straight line approximately 10 cm in length, with the pen held vertically. Draw as fluently as possible, to ensure a consistent movement throughout.

4. Repeat for the second recording.

5. Right-click the first recorded trial and select "Test Linearity".

6. You can observe the straightness and smoothness results in the "Device Units vs. Sample Number" chart. The subsequent chart contains the Missing Sample Estimator.

7. Closing the Raw Data Chart, you will find the test results in the results window in the bottom section of MovAlyzeR®.

8. In the results window, you will find the spatial and temporal errors.

9. Repeat this process for the second recording. Using the best results, you can compare the calculated accuracy with that specified by the tablet manufacturer.

Demonstration video Click to download a video of the testing procedure.


The following pen tablets have been tested by NeuroScript. The full details can be found by clicking the tablet name in the first column.

Tablet. HxW (in.). Pen Acquired Resolution (cm) Acquired Sampling Rate (Hz) Measured RMS coord. error (cm/units) Measured Missing/Extra Samples (%)
Wacom Graphire4 6x8 Grip Pen .00125 100 0.0032 / 2.5 0% / 0%
Wacom Graphire4 6x8 Ink Pen .00125 100 0.0055 / 4.4 0% / 0%
Wacom Graphire3 6x8 Grip Pen .00125 100 0.0016 / 13 0% / 0%
Wacom Graphire3 6x8 Ink Pen .00125 100 0.014 / 11.4 0% / 0%
Wacom Intuos3 6x8 Grip Pen .00125 100 0.014 / 11 0% / 0%
Wacom Intuos3 6x8 Ink Pen .00125 100 0.0071 / 5.7 0% / 0%
Wacom Intuos3 9x12 Grip Pen .001 100 0.0096 / 9.6 0% / 0%
Wacom Intuos2 6x8 Grip Pen .0005 100 0.0019 / 3.7 0% / 0%
Wacom Intuos2 12x18 Grip Pen .0005 100 0.0014 / 2.8 0% / 0%
Wacom Intuos 6x8 Grip Pen .0005 100 0.0029 / 5.7 0% / 0%
Aiptek 8000U 6x8 .00508 150 0.0072 / 1.4 33% / 0%
Aiptek 12000U 9x12 .00508 150 0.017 / 3.37 0% / 0%
GTCO Calcomp CAD Pro 6x9 .00254 75 0.013 / 5.08 0% / 0%

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