With the “Teach” method, there is always a buffer of 10% in the upper and lower parts of the measuring range. Higher strain signals, for instance, in the event of a failure are amplified and transmitted. The electronics, thus, are not set between 0 and 10 V but between 1 and 9 V.
The characteristic curve, i.e., the ratio of the strain and the output signal, can also be negative. Both shortening and elongation can be converted into a positive signal. Therefore, it makes no difference whether a shortening (negative strain) or an elongation (positive strain) is considered, as the integrated electronics can convert both strains into a positive output signal. The decisive factor is the point which is acquired first and defined as the zero point. The built-in measuring amplifier provides low noise and a bandwidth of 2 kHz and is thus well-suited for dynamic processes.
It is essential to permanently store the span, i.e. the difference between the minimum (the zero point) and the maximum (the maximum force applied). The zero point, on the other hand, is not permanently stored and it gets lost after a power failure. Therefore, it is imperative to reset to zero after a power failure. However, a re-calibration is not necessary.
It should also be noted that there is a lower strain limit to which the sensor can also be calibrated. This limit makes sense since otherwise, the electronics’ noise might become too strong. The zero position and the strain at the maximum applied force must always differ by 50 µm/m. A smaller difference results in the electronics failing to complete the teach-in process. With steel structures, this corresponds to a material stress of approximately 10 N/mm2 which facilitates its use even with very low strain levels, i.e., with very stiff structures.