Reply #154: There are such things as Thermal Drift

[Grinchie]

Thermal Drift is when electrical components change in Resistance, Capacitance and Impedance when they heat or cool. It can cause electrical signals to shift around, and this is certainly true with a touch screen.

A good example is a device called a Thermistor, which changes it's resistance in a precise manner depending on temperature. The resistance chance so precise and predictable, that it is used in digital thermometers. Regular resistors are not supposed to do this, but they can. In fact, nearly everything can drift given differing heat. It can be acceptable in some applications, unacceptable in others.

An example is when a machine is cold and turned on. It is then calibrated by clicking 4 check boxes in various parts of the screen. This "Sets" the coordinates for the Chip that translates impulse to Logical Coordinates.

As the device warms up, the electrical impulses may "Drift", and if the Drift is significant, the Logical Coordinates derived from the electrical impulses could be considerably different than the one detected when the machine was cold. This is a Normal, Documented effect present in ALL electronic devices.

The machine just needs to recalibrated to the new coordinates, but you can assume that the Polling workers don't even think about the possibility of Thermal Drift, or they have been explicitly not told about it.

As a Software and Electrical Engineer, I would never ever ever use an Electronic Voting machine unless it gave me a receipt.

These things are manufactured like Consumer Items and are not subjected to any rigorous testing or manufacturing standards for Software or Electrical components.