Knowledge Base

Orientation of Metric Inclinometer Probe

1. Introduction
This article highlights the differences in orientation and use between the Soil Instruments Inclinometer probe, the Slope Indicator probe and RST Inclinometer.

2. Differences between the probes
The industry standard dictates that when an Inclinometer probe is tilted in the direction of the expected movement (commonly referred to as the A0 direction) the resulting data will be a positive value, with the probe tilted away from the A0 direction (A180) the resulting data will be a negative value. With the A0 direction identified the inclinometer casing will be installed ensuring on one of the casing keyways is aligned with the A0 plane. This keyway is then identified/marked as the A0 keyway. The inclinometer probe is then inserted within the casing with the leading wheel aligned in the A0 keyway.

It has been highlighted by customers that when using an Soil Instruments Inclinometer with the same methodology that is used with a Slope and RST Inclinometer systems the results from Soil Instruments Inclinometer display an opposing sign value. We have reviewed the other systems and would like to offer an explanation on the reason for the differences.

We can confirm that with a Soil Instruments Digital Inclinometer system the lower wheel is defined as the leading wheel. It has been this way since Soil Instruments first started manufacturing Inclinometers in the 1960’s. We can also confirm that the Slope Indicator Inclinometer system defines their leading wheel as the upper wheel, similarly with the RST system. As you can then see, if a Soil Instruments Inclinometer is used with the same methodology as the Slope Indicator and RST Inclinometer systems, with the upper wheel used as the leading wheel, the results will be inverted.

Using the Soil Instruments Inclinometer system as stated within the manual (lower wheel as the leading wheel), you will receive the correct data values. The use of the lower wheel is the current, and what has always been since the 1960’s, standard practice for Soil Instruments Inclinometers (Lower wheel in the A0 direction resulting in positive results). It is also important to note the B0 and B180 directions on a Soil Instruments probe. The B0 direction can be found by rotating the probe 90 degrees clockwise from the A0 position, whilst the B180 position can be found by rotating the probe 90 degrees anti-clockwise from the A0 psoition.  
 
The user should consult with the manufactures instructions on how to take readings with the Inclinometer. Importantly the user should review and ensure they understand which wheel on the Inclinometer probe is defined as the leading wheel. 

3. Correcting readings if they have been taken in the in-correct orientation


Figure 1. Example of inverted readings

If you have taken readings with a system in the wrong orientation (Figure 1.) and are using In-Site software for the the data interpretation and presentation it is possible to re-align the new incorrect results with previous results. This is a reasonably simple process that has to be done on each incorrect reading set. This is commonly very obvious when readings have been taken in the wrong orientation as the readings will show a large deflection in the opposite direction. To correct the readings you will need to: