Editorial Feature

What is an Inclinometer?

The inclinometer system consists of an inclinometer casing and an inclinometer measurement system. The casing provides contact for sub-surface measurements, while its grooves control the orientation of the inclinometer sensor and provide a uniform surface for measurements.

The casing is usually installed in a borehole; however, it can also be buried in a trench, cast into concrete or attached to a structure.An inclinometer, or clinometer, is an instrument used for measuring angles of slope/tilt and elevation/depression of an object with respect to gravity. They are known by various names, including gradiometer, tilt indicator and slope gauge.

Types of Inclinometers

Inclinometers are broadly divided into two categories:

  • Inclinometers that use a gravity-actuated pendulum or other indicators
  • Inclinometers that use a spirit vial

Modern inclinometers use various technologies. The following are some examples of inclinometers in combination with other technologies:

  • Electronic inclinometer – This enables very precise readings of angles. This type of inclinometer uses an internal gyroscope to measure the direction of gravity's pull. The gyroscope remains in one position, no matter the orientation. A solid object is placed along the gyroscope, and the angle between the gyroscope and the object is determined via the inclinometer and displayed on an electronic readout.
  • Mercury inclinometer – Similar in operation to an electronic inclinometer, but instead of the gyroscope, mercury liquid is used.
  • Manual Inclinometers – This is an older model of inclinometer also called the gas bubble type. The instrument contains a glass tube with liquid and an air bubble inside. As the instrument moves, the bubble stays level. Its position indicates the incline angle on a scale.
  • Gravity inclinometer - One of the most practical gravity inclinometer was invented by William B. Melick in 1889. His instrument consists of a rotating scale and fixed pointers. The scale is driven by an internal pendulum weight. The weight is fastened to the back and suspended from a bearing, which is supported in the front by a diagonal cross-piece. There are two buttons on the instrument that can be pressed so as to lock the scale firmly in place to enable easy reading. This instrument is considered to be a sturdier and more practical design because whatever the orientation, the weight is kept down by gravity, while the scale moves.

Working Principle

Inclinometer deflection devices comprise a servo cable, cable reel, accelerometer probe, and a digital readout unit. Care should be taken while setting up this instrument to take a set of readings by ensuring that the guide wheels are checked for bearing free play and tightened if required. Lubricant should be applied to the wheel bearing assemblies. The cable connectors are protected with caps to prevent damage or contamination to the connector contacts. An O-ring is used to provide a water-tight seal between the probe and the cable.

The readout unit is turned on and the system is checked by holding the bottom of the probe in a stable position while moving the top along the measurement axis, i.e. the two upper wheels. The readout unit will display values with polarity matching the given tilt angles. The reading can be interpreted using basic trigonometry.


The following are the key application areas of inclinometers:

  • For determining latitude using Polaris or the two stars of the constellation Crux
  • For determining the angle of the Earth's magnetic field with respect to the horizontal plane
  • For indicating a deviation from the true vertical or horizontal
  • For survey purposes especially to measure the angle of inclination or elevation
  • For adjusting a solar panel to the optimal angle so as to capitalize on its output
  • To alert an equipment operator if a machine may tip over
  • For measuring angles of elevation, slope, or incline e.g. of an embankment, measuring movements in walls or the ground in civil engineering projects, measuring steepness of a ski slope, measuring the slope angle of a tape or chain during distance measurement, and measuring the angle of drilling in well-logging
  • For measuring the inclination angle of the pelvis and measuring Range of Motion in the joints of the body
  • In geophysics for monitoring volcanoes and for measuring the depth and rate of landslide movement.
  • For monitoring the boom angle of cranes and material handlers
  • For measuring the height of a building, tree, or other objects using a vertical angle and a distance using trigonometry
  • For use in structural geology

Sources and Further Reading

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