Abstract: A device for positioning the tip of an elongated probe (14) at a selected station of a holding plate (12) includes motors to move the holding plate and a supporting stage within a coordinate plane (mxy). The elongated probe is also movable along a linear probe axis that is orientated normal to the coordinate plane (mxy). A camera creates a pixel image of an optical marker placed on the stage. The image defines a coordinate plane (pxy). To relate the coordinate plane (pxy) to the coordinate plane (mxy), the optical marker is moved to successive locations in the mxy plane and a pixel image is obtained at each location. Using the pixel images, a computer calculates the relationship between coordinate planes and uses the relationship to signal the motors to move the holding plate in the mxy plane and position the selected station on the probe axis for interaction with the probe.