Linear position sensor technology used in various applications is typically chosen based on specific parameters and characteristics. For most rugged applications, one of the most commonly used linear position sensors is the LVDT or linear variable differential transducer.
Since the earliest introduction of an LVDT as a laboratory device, it has consistently expanded in functionality as a reliable sensor for industrial, commercial, subsea, and sophisticated process control applications.
What sets LVDTs apart from other sensor technologies is that it is a highly reliable feedback device. Manufacturers continue to experiment with the capability of LVDTs to withstand harsh working conditions which has further expanded the suitability of LVDTs for different types of working environments.
DC and AC-operated LVDTs
Earlier versions of LVDTs used AC processors to condition the device’s signal. Unfortunately, it takes longer to calibrate an AC position sensor, and the assembly is also more expensive. These concerns were prohibitive and did not allow for the widespread application of this type of sensor technology.
The invention of cheaper microprocessors made it possible for manufacturers to embed the signal conditioning within the device but at the same time keep the device small and compact. A DC-operated LVDT has all the characteristics of an AC-operated sensor but makes the assembly simpler, and less expensive.
Another notable benefit of a DC-operated LVDT is that the output produced is compatible with a digital or computer-based system. These sensors also have superior immunity to error caused by noise. The operator can easily read the data which is directly fed into computer software.
But there are times when an AC-operated LVDT is more suitable. Since the device does not include internal electronics, it is not susceptible to shock and vibration. Manufacturers can assemble a more compact AC-operated LVDT for installation in machines and equipment that are subject to these conditions.
Improved performance through modern electronics and manufacturing techniques
In general, both AC and DC-operated LVDTs are highly reliable, repeatable, and robust. But modern electronics and manufacturing techniques are improving the technology even further. Apart from overall better performance, advanced winding techniques and compact microprocessors have also improved the LVDTs stroke-to-length ratio. As such, LVDTs today are now suitable for application in hydraulic and pneumatic machines.
Another limitation of early LVDT technology was environmental sensitivity. Materials such as titanium, nickel, and alloy used to manufacture LVDTs allow these sensors to withstand harsh conditions which involve extreme temperatures, radiation, and high-pressure situations. There are many applications, such as subsea conditions subject to pressures of 3500 psi which pose a difficulty for most types of sensors, but not modern LVDTs. Hermetic sealing is also used to protect sensors from the effect of corrosive fluids.
Due to these advanced construction methods, LVDTs are now considered as one of the ideal types of position sensors used for industrial applications. The mining, manufacturing, agricultural, and aerospace industries all use LVDTs as a preferred feedback device for various equipment and machines that are often subject to the harshest working conditions. The humble beginnings of LVDTs as a laboratory tool have completely evolved into a sophisticated device critical for many modern applications.
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