1. Function principle, advantages, and limitations of strain transducers
Strain transducers, such as HBM’s SLB, have proven their value in many measurement tasks. They can be easily attached to existing structures with screws. Typical applications include presses, welding machines, silos, etc. For instance, when a press stroke is initiated in a press equipped with a strain sensor, it results in a strain in the press frame that is proportional to the pressing force. The strain transducers convert this strain into a measurable electrical signal that enables the force, in this case, the force exerted by the press, to be derived.
The advantages of strain transducers are clear:
- A strain sensor is available at a considerably lower price than a force sensor; this applies, above all, when compared with force transducers for use with large forces.
- Strain sensors do not impact the system’s stiffness. Hence, the machine’s dynamic properties do not get affected.
- Force transducers for use with very large forces, especially, require some additional space. This means that the measurement system’s structure is modified, which presents a problem, especially if it is to be offered only as an option.
However, set against these advantages are some drawbacks:
- Strain sensors are in no way as accurate as force sensors. This is a crucial factor, as there is an increasing demand for higher accuracy in production.
- Strain transducers must be calibrated after mounting. Calibration means that the force exerted in the process first needs to be measured with a force sensor, such as the C6A. It is then compared with the strain transducer’s signal and subsequently, the strain is converted into a force. The calibration can also be performed using known weights. In this case, the accuracy of the subsequent measurement cannot be better than the accuracy of the calibration process.