Fast sensor teach-in. This is how it’s done:
Unlike our product, that is, the SLB700A/06VA, other available strain sensors with an integrated amplifier module only have a fixed amplification. For instance, 500 µm/m correspond to an output signal of 10 V. The fundamental drawback of this method is that the maximum output signal depends upon the given amplification, which cannot be changed. If, in the example above, a strain of 200 µm/m is utilized as the input signal, the resulting output voltage is 4 V. Particularly, when the next element in the measurement chain is a module that has a low resolution or increased noise (i.e., when economic aspects are of paramount importance), the results often are unsatisfactory.
SLB700A/06VA strain sensors from HBM, with integrated amplifier electronics, manage to bypass this problem, since they provide the maximum possible output signal at any time, independent of the intended purpose.
In order to achieve this, HBM has developed an extremely simple “teach-in procedure”.
- First, the sensor is installed in the usual manner, and the load on the machine (press, roll stand, silo) is reduced to zero. A longer pulse sent to the teach-in input is sufficient for the electronics to memorize the zero point.
- Subsequently, the maximum load is applied, sending another (this time, a SHORT one) pulse to the teach-in input is sufficient. Now, the electronics is adjusted between these two points.
- This enables the input range of the next level to be fully utilized at any time.
- There is always a buffer of 10% in the upper and lower parts of the measuring range. Higher strain signals (e.g. in the event of a failure) are amplified and transmitted.
- The characteristic curve can also be negative. Both elongation and shortening can be converted into a positive signal.
- The built-in measuring amplifier provides low noise and a bandwidth of 2 kHz.
- It is essential to permanently store the span, i.e., the difference between the minimum and the maximum. Therefore, it is imperative to reset to zero after a power failure.