The North American market for linear displacement sensors including encoders, linear variable differential transformers, laser systems, magnetostrictive, potentiometric, capacitive, inductive, and ultrasonic products totaled $338.7 million in 2006, according to a market study by Venture Development Corp. Displacements are occurring in many applications, as evidenced by the varying and changing growth rates for all primary technologies.
The largest product market is for LVDTs, and by far the largest shipments of these are for military/aerospace applications, particularly for use on aircraft, reports VDC. These have a long operating life in harsh environments. LVDTs have only one moving part and little friction between the moving ferromagnetic core and the cylinder in which it moves.
LVDTs
The North American LVDT market peaked out in 1999 and then slumped off in the 2000 and 2001 time frame, but has been recovering since, and is expected to continue growing over the next five years. On the military side, defense projects have been strong since the beginning of the Iraq War, and this is expected to continue and sustain market growth for LVDTs, predicts VDC.
Optical Encoders
From 1994 through 2006, the North American optical linear encoder market grew at about a 10.5% compound annual growth rate. These are used principally in industrial applications on metalworking equipment, electronics and semiconductor manufacturing equipment, and assembly/robotics equipment, but also find other uses such as on medical equipment. Optical encoders can provide high accuracy, and being digital output products require no A/D conversions for use in digital control systems. The growth rate for these products is expected to slow over the next five years, but to remain above average. The highest growth rate is forecast for use on elevators, says VDC.
Magnetostrictive
The North American market for magnetostrictive linear displacement sensors increased at just over a 5% CAGR between 1994 and 2006, according to the study. These sensors find extensive use with pneumatic and hydraulic cylinders, and are particularly useful for long strokes. These provide high resolution, and repeatability.
The overall North American market for these products is expected to grow at an above-average rate over the next five years, with the highest growth rate expectations for use in metalworking, medical, assembly/robotics equipment, and valve applications, reports VDC.
Potentiometric
In contrast, the North American market for linear potentiometric displacement sensors declined at about 5.3% per year over the past 12 years, says the study.
The cost, and thus price, of linear displacement measurement potentiometers vary considerably, being among other things a function of volume, length, linearity and accuracy. For example, linear potentiometric sensors are most heavily used as components in transportation vehicles for pedal positions, power seats positioning, and power steering. Typically these products are relatively short displacement devices, with low linearity and accuracy requirements. The material cost to produce these is low, and because these are purchased in large volumes for use on automotive vehicles, the resultant price is low. This market segment has shown very little decline over the past 12 years, particularly as more position sensors have been added to automotive vehicles for a variety of functions, the study explains.
In other applications, particularly military and industrial, often high linearity and accuracy are required, and often these are much longer products, and purchased in much lower volumes. Prices on these products are considerably higher. The most displacement of linear potentiometric sensors has occurred in these segments, particularly in industrial applications. For example, between 1994 and 2006, the North American packaging equipment market for these sensors declined about 90%, that for industrial engine controls by 70%, for metalworking equipment by 58%, for plastics and rubber manufacturing equipment by 50%, and for medical equipment by 39%, reports VDC.
Potentiometric linear displacement sensors are contact devices, and have a relatively short operating life because of wear caused by friction compared to other types of linear displacement sensors. Expectations are for continuing loss of market share for these products.
High Growth Product Markets
The highest growth rates forecast in the VDC study are for laser systems at a 10.2% CAGR, and capacitive linear displacement sensors at 8.0%. The markets for both are currently relatively small, however, each is expected to grow since OEMs and end users are seeking higher accuracies, which these provide. This is particularly the case in the semiconductor and electronic industries where more precise measurement capabilities enable shrinking the size of electronics.
Where will the market be in five years? Optical linear encoders have enjoyed a strong ride to toward the top, but the market for the two above categories, and a few other technologies, are forecast to have higher growth rates.
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