Combining high stability and accuracy with robust mechanical properties, bonded foil strain gauges have earned a dominant role in sensor applications in the oil and gas industries.  As with any sensor technology, however, environmental factors such as temperature and humidity can affect these devices, introducing measurement drift in applications that require accurate, stable sensor performance. Through careful selection of sensors and associated materials, however, engineers can mitigate causes of drift in these devices and rely on them in diverse applications that depend on reliable measurement of load, torque, tension and pressure.

Bonded foil strain gauges take advantage of the resistive effect, where the resistance of a conductor changes in response to mechanical strain. In these devices, metallic foil is arranged in a grid pattern and bonded to a thin carrier in a manner designed to enhance the effect of mechanical deformation in changing the resistance of the foil conductor. When the device is attached to an object, the foil resistance changes in proportion to the magnitude of the forces acting on that object. By carefully monitoring that change in resistance, sensor systems based on these devices can provide accurate measurement of forces acting on equipment and structures.

Their ability to operate accurately under heavy loads in harsh environments makes bonded foil strain gauges ideally suited to the needs of the oil and gas industries (Figure 1). Indeed, these devices play a critical role in ensuring optimal operation and safety in high-stress applications, including pump-off control and polished rod end load cells on well pumpjacks (also known as reciprocating rod lift pump systems) and deadline anchor load cells. Their robust characteristics also find application in high-pressure applications, including hammer union pressure transducers, as well as liquid and gas pressure measurements on equipment such as diesel engines, hydraulic power units (HPUs) and nitrogen pumping units.