Collection of biological fluids. The system and method comprise a display that includes at least one display element responsive to palpebral movement information from the eye sensor. An integrated circuit including a microcontroller, a DAC selected from a group consisting of a string DAC and a current source DAC and an operational amplifier coupled to the DAC output. An interference condition occurs and the mechanical advantage of the threads rotationally pull the tapered head into the counterbore. One end of the ruler has an extension of eyelet molded thereon and the other end of the ruler has a depression molded into an under surface of the ruler.