University of New Mexico

Civil Engineering Department

Civil Engineering Materials Laboratory, CE 305L

INTRODUCTION TO MEASUREMENT DEVICES

Objective

Lab 1 was an introduction to the Civil Engineering Materials laboratory. As part of this introduction, a variety of measuring devices used in the lab were explored and calibrated.

Scope of Work

Data obtained in this lab includes the following:

• Calibration data for an LVDT.
• Calibration data for a 100,000 lb proving ring using the Tinius Olsen 120 kip Universal Testing Machine (UTM).
• A series of measurements using calipers, tape measure, pi-tape, and micrometer.

See table 1.1 for all equipment used in this lab.

Procedures

To download procedures for introduction to measurement devices click here

1.Calibrate the LVDT

Calibrate the LVDT using an excitation voltage of 18 VDC. Use the Schaevitz calibrating micrometer over a total length change (displacement) of 0.5 in. (use 0.1 in. increments). Tabulate the voltage versus displacement. Plot the data and determine slope of graph. Report the sensitivity of the LVDT in units of inch/VDC.

2. Calibrate the Proving Ring

Calibrate the 10,000 lb proving ring using the Tinius Olsen 120 kip UTM on the 60,000 lb range. Obtain load readings in 10,000 lb increments between 0 and 50,000 lb. Record the proving ring displacement at each load readings. Plot the data set displacement vs. load. Determine the slope which is the sensitivity of the proving ring in lb/in. (this is also the spring constant).

3. Series of Measurements

a. Measure the 2 in. by 2 in. Douglas Fir specimen. Measure the length, width, and thickness. Use the tape measure for the width measurement and the calipers for the other two dimensions. Report the measurements.

b. Measure the cyclical plastic specimen. Use the calipers first then the Pi-Tape. Report the values and percent error.

c. Measure the 0.5 in aluminum specimen using the calipers and micrometer. Report the values and percent difference.

4. Table of Various Measuring Devices

Complete the table for various measuring devices on display in the lab. Make sure to state units and best resolution.

Table 1.1 displays some of the available equipment in the mechanics of materials laboratory.

From the linear trend line in the above chart, the sensitivity of the LVDT is –0.056 in./VDC .

Problem #2 Calibration of the 100,000 lb Proving Ring

The sensitivity of the proving ring is the slope of the load vs. displacement in (lb/in). From the above chart and trend line this value is 1.48(10 6 lb/in.) . This value is also the spring constant of the spring.