Electrical surges due to lightning are common sources of sensor and data acquisition equipment failure and can be protected using sensor line surge arrestor packages and gas discharge tubes which absorb the bulk of the transient and discharge it to earth ground.
Linear digits (B units)
In order to overcome the problem of a linear conversion, the frequency value can be squared, thereby rendering it linear, but quite large. To reduce its size, it is often divided by 1000 (or multiplied by 10‑3). The expression Hz2/1000 (or Hz2 x 10‑3) is the most commonly adopted as a ‘linear’ digital output. (B unit).
Load distribution plate
Used with a load cell in order to ensure that the load is applied equally over the annular loading surface of the cell. It is inserted between the load cell and the anchor head (wedge plate).
For vibrating wire load cells, two will be required whereas for strain gauge and hydraulic, only one is required.
Long term deformation
The tendency of a solid material to move slowly or deform permanently under the influence of mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. The rate of deformation is a function of the material properties, exposure time, exposure temperature and the applied structural load.
Low air entry filter - LAE
LAE (Low air entry). Is a term used for a piezometer filter type. This often causes confusion as LAE means 'low RESISTANCE to air entry'.
LAE filters are typically used in non-cohesive and highly permeable media. Whilst they do not need to be saturated prior to installation, it is good practice to do so.