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Intrinsically Safe Absolute Rotary Encoders

In the most hazardous environments, where an explosive atmosphere consisting of flammable gas or vapor is regularly present and a sensor fault cannot be risked, Intrinsically Safe (IS) sensors may be the best sensing option. Generally, these sensors are paired with a barrier which limits the amount of electrical and thermal energy that can enter the Hazardous Area to an amount that is so small that even in the situation of a sensor fault, there is not enough energy to cause an ignition.

Image showing Zones 0, 1 and 2. Image credit Atexshop.com .

The number of rotary encoders that are available for these types of environments is extremely limited. And while there are a few options for incremental encoders, for an absolute encoder the Positek E/G/H/M/X 50_ series stands alone in the market. Based on Positek’s patented PIPS technology, these sensors offer absolute single turn measurement with linearity of up to 0.1% full scale and an easy to read voltage or current output. And unlike contact-based potentiometers that can wear out and dither with use, Positek sensors are based internally on non-contact inductive sensing, providing years of reliable use in the harshest environments.

Another advantage of using the Positek rotary encoder is when used as intended with a G/X 005 series galvanically-isolated-amplifier-barrier (from here simply referred to as ‘the barrier’), the signal can be sent to a controller up to 1000m away from the barrier when appropriate size cable is used. Furthermore, by using a ‘5 wire connection’ between the barrier and sensor, the barrier can compensate for the voltage losses over the wires to the sensor and thus there is no loss of linearity by having long distances between the two.

Safe and Hazardous Areas and the use of a barrier to limit the amount of energy that can enter the Hazardous area.

For applications where only a partial turn is needed Positek’s E/G/H/M/X 500 series sensor offers a compact design and up to 160 degrees of measurement. For applications where larger measurement angle is required, the 530 series can be used, providing a full 360 degrees.

Postiek P500 series sensors are compact at about 1.5” in diameter and are available in a variety of different form factors to adapt to the existing mechanics of a given installation.

Based on the specific application, ATEX and CSA US rated sensors are available for gas and dust as well as vapor and mining. See below table for details.

Positek Hazardous Environment Flow Chart:

To the best of Everight’s knowledge, these combinations are the only Intrinsically Safe absolute encoder option available on the market.

DISCLAIMER: Any device selection for a hazardous environment should be reviewed by a local safety engineer who has knowledge of the requirements and systems in place. 

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