Answer: ASTM now has a practice that lists the necessary equipment and method for verifying the calibration of your probe. However, in many cases, your data and graphs can go a long way toward satisfying your verification needs:
- The bottom 10 feet of your casing should be installed in stable ground. This way, you are assured of a stable reference. (To be more exact, we recommend that you install 5-reading intervals of casing in the stable ground, thus with metric casing, this would be 2.5 meters.)
- Since the bottom of the casing is stable, your surveys should show no movement at all within that ten feet. Any movement that you see is error. Thus you have an in-situ test stand.
- With this in-situ test stand, you don't need to perform any explicit tests. The information you need to check your probe is embedded in your readings.
- This in-situ method of checking the probe is better than the test stand method for several reasons: First, the installed casing is more stable than any test stand on the surface. Second, the information is embedded in each inclinometer survey, so it won't get lost. Third, the embedded information shows the condition of the probe at the exact time of the survey.