The standard graphs

The StabiAlert sensor

The StabiAlert sensor measures two physical units:

  1. Tilt (Direction of gravitation)  [DEG]
  2. Acceleration [m/s2]

Each standard graph consists of 3 parts:

  1. Part 1: two plots with black lines.
  2. Part 2: two plots with red lines.
  3. Part 3: three plots with respectively a green, blue and magenta line.
The three different parts of the standard graph.

Tilt (gravitational measurement)

Tilt (part 1)

The sensor measures tilt in two directions. The X-direction and the Y-direction. The sensor is sensitive enough to register more severe earthquakes from the opposite side of the globe.

They measure both tilt directions at a rate of 100Hz. In standard operation they report every 15 seconds the average, lowest value and highest value to the central server system in the cloud.

From these numbers we generate two values per channel. Respectively the average tilt and the vibrations.

The graph below show the tilt of a building in both directions during a period of 14 days. The tilt is expressed in degrees. [DEG(360)]. The first line is the tilt in X-direction and the second line the tilt in Y-direction.

The tilt of a building during 14 days.

It is completely normal for a building to wobble a few thousands of a degree during the day.

Almost all buildings "wobble" on a daily base

Vibrations (part 2)

These two plots with red lines show the vibrations of the structure in both directions.

In standard operation every 15 seconds the difference between the highest measured value and the lowest measured value is plotted in these graphs.  Hence, even if a very fast passing vibration "shakes" the building, the extreme values within these 15 seconds will show up here.

The part Vibrations is an indicator of how stable the object and/or its environment is. The vibrations are also expressed in degrees [DEG(360)].

Vibrations recorded during a 14 day period

The Accelerometer

The Peak Accelerations. (Part 3)

When mounted to a wall the sensor measures the acceleration of the wall (or at least the location where it is mounted) in three directions:

  1. In X-direction (green)
  2. In Y-direction (blue)
  3. In Z-direction (magenta)

All channels (directions) are continuously sampled with a sample rate of 400Hz. In standard operation every 15 seconds the peak values of all channels are reported to the central server system in the cloud. From these graphs one can not derive the direction of the peak (ground) acceleration solely its absolute value.

All accelerations are expressed in the standard SI unit: m/s2 (metre per square second)

At 10:36 a shock was recorded.

Depending on the type of event (e.g. a passing lorry, earthquake, piling, etc, ...) the sensors will show different readings. It is normal that sometimes the tilt sensors show clear vibrations (in case of (very) low-frequencies) and the accelerometer shows no reading. On the opposite, in case of high frequencies the accelerometer shows clear readings while the vibrations show no readings. On some occasions both instruments clearly show extra ordinary values.