direction. Am I correct in thinking (that in order to use the part most
effectively) the ADXL321 would have to be assembled to a board whose plane lies
in the vertical and perpendicular to the direction of acceleration?
No that is incorrect.
Both axes of sensitivity of the ADxL321 are in the plane of the IC and circuit
Therefore if you place the board flat on the desk in front of you, the
ADxL321 can detect acceleration as you slide the board around the desk (like a
It cannot detect the acceleration if you lift the board vertically off the desk
(again like a mouse).