As an inquisitive trade journal editor and modest Star Trek fan, there’s a certain allure to one of that program’s many devices: sensors. I recently discovered more about the fascinating world of sensors, but for packaging, not for starships. More…


As an inquisitive trade journal editor and modest Star Trek fan-though I fall a parsec short even of my wife’s knowledge regarding the starship Enterprise and its personnel-there’s a certain allure to one of that program’s many devices: sensors.

I’ve had occasion over the years to be drawn into electronic topics while working on stories involving radio-frequency identification as well as in machinery articles. My interest in such things relates to a lifelong fascination that I’d wished I’d cultivated more, starting in college when I dropped an elective course in electronics because I’d found that I already had enough credits to graduate.

Of course the real world of sensors in packaging applications is light-years removed from science fiction, so don’t expect to be stunned by any technical revelations. Nonetheless, the speed and capabilities of today’s sensors are eye-opening. Applications for photoelectric sensors abound throughout packaging operations, ranging from baggers to conveyors to labelers to printers and label applicators.

For example, a sensor can detect printed registration marks to identify the gap between print impressions to prompt the cutting of bag film on a form-fill-seal machine. I’d like to share some of what I learned during a recent conversation with Tim Kelley, VP of business development & marketing for Tri-Tronics Inc., a manufacturer of photoelectric devices and related components.

Kelley defines a photoelectric sensor as a pulse-modulated light synchronized to a detector that responds to light that’s either reflected off a surface or blocked by an object.

As in most things related to packaging, it wasn’t surprising to hear of a sustainability angle: improved accuracies for machinery and sensors equals less film waste and more bags on a roll as the printed gap between bags shrinks. It can also mean less ink on film in the first place.

Over the years, the all-important light source for sensors has evolved from a light bulb to ever-improving light-emitting diodes (LEDs). Currently, LEDs are close to the “pure white” portion of the spectrum and are brighter than ever. Other portions of the light spectrum, such as red, blue or even ultraviolet, may work better for the particular application, Kelley notes: “Especially for clear packages such as bags, it’s often desirable from a package graphics standpoint to remove the visible registration mark. With a color sensor using pattern recognition, the edge of a logo or other repeatable graphic element can work in place of a registration mark.”

The Tri-Tronics sensor for one OEM customer’s shrink sleeve applicator has a response speed of 10 microseconds, which equates to a rate of 1,500 sleeves per minute with just a 1/8-inch gap between sleeves.

Other developments he notes:

  • Photosensors that are able to meet IP69K standards that can withstand a washdown at up to 1,500 psi-strong enough to remove labels from containers, Kelley says.
  • Sensors that can communicate with the human-machine interface (HMI) panel so that adjustments can be made through the panel.
  • True shade-to-shade analog or digital color matching for exceptional accuracy. “The capability of a spectrometer at the price of a sensor,” he remarks.
  • If there’s one myth about sensors that Kelley would like to overturn, it’s the desire by engineers to adjust a sensor once and then not have to EVER touch it again. “That’s impossible even through an HMI,” Kelley says, “though with that they don’t have to physically touch the sensor.”

    Even if the product the sensor is detecting never changes, there is still the degradation of the LED to contend with, he says. This can be due to things such as a scratch on the lens or dust from the environmental. In fact, dirt collection is the most common source of sensing errors, Kelley points out, one that can be fixed with the quick swipe of a cloth over the lens.

    Time for me to journey on to other duties, but hopefully this brief editorial trek into sensors has been, as Mr. Spock would say with slightly raised eyebrows, somewhat “fascinating.”