Question

Briefly explain how the micrometer works (i.e. what one full rotation of the rod means, the relationship between “horizontal” and “vertical” increments on the micrometer, and how the distances are converted to a voltage measurement.) What is the relationship between voltage and displacement, as examined in the LVDT experiment? Were the voltage readings within the linear range of the LVDT? After taking a few readings, was the voltage reading still zero when you returned to 0.500 inches on the micrometer? Explain.

Answer 1

A micrometer consists of a thimble and a screw system. The screw system has a certain pitch depending on requirement and manufacturing company. The screw system has a thimble enclosing it which is rotated to achieve required dimensions. The screw(also called a spindle) has a minimum pitch which is 0.5mm in the metric system or 0.025 inches in the imperial system. One complete rotation on the spindle gives a displacement of 0.025 inches. The markings on the circular scale give us values between the range of 0-0.025 inches as displacement for higher accuracy. Hence, the horizontal and vertical scales are directly proportional.

The voltage displacement is directly proportional to the micrometer displacement in the LVDT experiment i.e increase of 0.5 inches on the micrometer scale corresponds to a linear increase in voltage, say 1V. Further increase of 0.5 inches leads to an increase in the voltage by a similar amount i.e 2V. Yes, the voltage readings were within the linear range on the LVDT experiment. After a few readings, the voltage readings are roughly 0, meaning, there maybe an error of about 0.5 - 1% depending on the apparatus and equipment.