Inductive proximity sensors typically mount so the objects they detect approach within 40 to 80% of the sensor target range.
— Robert Repas, Associate Editor
This range usually allows for all accumulated manufacturing and application tolerances. The sensing distances for standard cylindrical-type inductive sensors range from 0.8 to 15 mm. Thus, actual separation between the sensor and target is typically less than 12 mm — often significantly less.
Sensors positioned close to their moving targets are far more likely to suffer damage from physical contact. With machinery and equipment becoming increasingly compact, there isn't always room for additional mounting brackets or assemblies to properly hold sensors in position. A sensor that shifts or vibrates in position is more prone to collision damage. In this instance, many users prefer to use "extended-range" sensors to reduce the possibility of damage.
Extended-range sensors offer up to three times the range of standard inductive proximity sensors for the same-size housing. The longer sensing range reduces the likelihood of target-to-sensor collisions simply because the sensor mounts farther away from the moving target. Engineered for flexibility, extended-range sensors come in virtually all industry-standard housings and operating styles.
Extended-range sensors also help if the target is a nonferrous material such as aluminum or brass. When the correction factor for nonferrous metals is applied to extended-range sensors, the sensor ends up spaced almost a "normal" distance away from the target.—
Pepperl+Fuchs (am.pepperlfuchs.com) provided information for this column.