Replacing linear pots with non-contact technology

Resistive linear potentiometers are often used for position feedback in price-sensitive applications. However, since linear potentiometers rely on a contact-based operating principle, they often lack reliability and long-term performance. The Micropulse BIW, which replicates the form factor of traditional linear potentiometers, offers performance and reliability that linear potentiometers cannot. This is made possible by the Balluff-patented, non-contact, Pulsed-Inductive technology, which eliminates premature failure and performance degradation caused by mechanical wear. The Micropulse BIW, available in 0-20 mA and 4-20 mA versions, offers better noise immunity and allow longer cable runs compared to the linear potentiometer’s 0-10 V output signal. Other features include:

• Non-contact measurement technology for wear-free performance and long life
• Fast and easy drop-in replacement with its plunger style linear potentiometer form-factor
• Current output provides a more noise-immune signal

Typical resistive linear potentiometers are especially vulnerable to performance degradation caused by wear to the resistive element. Because the measurement principle relies on mechanical contact between the resistive element and conductive wiper, mechanical wear can lead to erratic output signals and, ultimately, unreliable process control. The Micropulse BIW linear position sensor solves these problems by incorporating noncontact, pulsed-inductive technology into a familiar, plunger style form factor. This patented technology provides high performance and previously unattainable reliability, while the mechanical form factor allows for hasslefree, drop-in replacement of linear pots. The BIW is available in stroke lengths ranging from 75 to 775 mm and offers continuous analog voltage outputs and now analog current outputs. The advantage of the new current output is superior noise immunity and ability for much longer cable runs than the voltage versions.

Hydraulic and pneumatic cylinders are often used as prime movers in industrial applications. In many of these applications, the capability to accurately and continuously monitor the position of the cylinder is desirable.

However, it is often not cost effective to retrofit an existing cylinder to accept an in-cylinder position feedback sensor. The Micropulse BIW is a low-cost, easy to implement solution. The BIW can be mounted directly to the cylinder body. If the cylinder has a locking mechanism that prevents the cylinder rod from rotating, the BIW’s plunger can be coupled directly to the rod. If cylinder rod rotation is a concern, the plunger can be coupled to the load that the cylinder is moving. The result is reliable, accurate, and inexpensive continuous position feedback.

Balluff Inc.

Dual-sensor, Split-connector Cuts Cylinder Costs

Three areas where you can look to cut costs on pneumatic cylinder applications include installation time, cables, and the sensors used for detecting the piston’s position. For example, first consider the sensor in a standard cylinder. Most standard cylinders use proximity switches, either internal or external to the aluminum housing that detect special targets or magnets mounted on the piston. Unfortunately, these proximity switches can be relatively expensive, take up valuable space, and are difficult and time-consuming to install.

A dual-sensor, split-connector system coupled to a multiple-interface block (MIB) in a high-density application reduces the number of wires and potentially doubles the number of cylinder switches that can be used in the same installation.

A better solution is designed around a new dual sensor with a split connector. The configuration has two low-profile, magnetic-field sensors molded together into a single, four-pole connector. Compared to the standard application (where the end of the piston’s stroke is detected in both directions), the dual sensor system does the same job with one less connecting cable, fewer terminations, and less connective hardware, which require less time to install. This dual sensor arrangement can cut an application’s cost by 50%.

Even in a smaller application, a dual-sensor, split-connector system installed on a cylinder to detect the end of a piston’s stroke can reduce installation time and material costs compared to a standard two-proximity switch arrangement.

A dual-sensor, split-connector system combines two magnetic-field sensors with a single connector. This approach uses only one four-conductor cable and less installation hardware with fewer terminations than the standard method.

In another installation where numerous cylinder switches are densely packed, multiple interface blocks (MIBs) are typically used to reduce the number of wires needed to return to the control panel. However, you get a bonus when you use a dual sensor system in the same installation: It doubles the number of cylinder switches that can be connected to the same MIB, or it cuts the MIB size in half for the same number of switches. Either way, your cost-cutting goal is realized.

Balluff
www.balluff.com/vtwin
jack.moermond@balluff.com