Automating Manufacturing Systems - Process Control and ...

continuous sensors - 23.18
stress
direction
uniaxial
rosette
Figure 23.19
Wire Arrangements in Strain Gages
A design techniques using strain gages is to design a part with a narrowed neck to
mount the strain gage on, as shown in Figure 23.20. In the narrow neck the strain is proportional
to the load on the member, so it may be used to measure force. These parts are
often called load cells.
mounted in narrow section
to increase strain effect
F
F
Figure 23.20
Using a Narrow to Increase Strain
Strain gauges are inexpensive, and can be used to measure a wide range of stresses
with accuracies under 1%. Gages require calibration before each use. This often involves
making a reading with no load, or a known load applied. An example application includes
using strain gages to measure die forces during stamping to estimate when maintenance is
needed.
23.2.4.2 - Piezoelectric
When a crystal undergoes strain it displaces a small amount of charge. In other
words, when the distance between atoms in the crystal lattice changes some electrons are
forced out or drawn in. This also changes the capacitance of the crystal. This is known as