In the Product Design & Development Brainstorm we talk with industry leaders to get their perspective on issues critical to the design engineering marketplace. In this issue, we ask:
What new encoder technologies are helping ease-of-use and cut costs in industrial applications, such as wind turbines, steel plants, or loading cranes? What helps protect equipment from damage due to loss of control, or personnel who might be in proximity to such equipment and where such a failure could cause injury?
One encoder technology has emerged that allows rotary encoders to last longer and handle higher vibration, shock, and temperature ranges, the magnetic-based encoder.
These Hall effect-based rotary encoders measure shaft rotation and develop the standard quadrature output signals without the glass disks used in optical-based encoder technologies.
When the Hall effect technology is used in absolute magnetic rotary encoders, the encoders may incorporate a Wiegand sensor, which allows the encoder to monitor and count shaft rotation even when power is not applied to the encoder.
This technique eliminates the need for other technologies, such as a gearbox or battery. Eliminating the multiturn gearing mechanism removes potential mechanical wear and the effects of vibration and shock, which can lead to breakage.
Batteries — their limited lifespan, extra weight and the need to replace them — are no longer required. Without the limitations, you can install your magnetic-based rotary encoders in harsher applications with wider temperature ranges.
They are more reliable, last longer, and save time and money by reducing machine downtime. Also, because of fewer mechanical components, magnetic absolute rotary encoders will be more economical to install than optical absolute rotary encoders.
The rotary encoder that not only helps to protect personnel, but also the machine and processes is the sine/cosine safety rotary encoder. The sine/cosine safety rotary encoder has integrated functional safety.
This integrated functional safety is achieved with an internal self-diagnostic that checks the analog 90 degree phase-shifted sine/cosine signal and calculates that Sine2 + Cosine2 = 1 to ensure the signal is functionally safe.
This safety encoder should have third party certification approved for SIL3, PL e, and Category 4. Having certified safety products simplifies the engineering complexity of the installation.
The safety rotary encoder should be used with a safe drive or safe speed monitor. The safe speed monitor, for example, safely detects stop (zero speed), over speed, and direction of rotation to ensure that the machine is operating within its limits.
This not only allows the machine to operate as needed, but also provides operators and maintenance personnel a safe environment to perform their work.
This article originally appeared in the October 2014 print edition of PD&D.
