Polar Bear Tough Cable Assemblies

As an electronics engineer, it’s not everyday you get a chance to take part in a project that combines polar bears, global warming and cable assemblies. So when you do, it’s a memorable one. For Meridian Cable technical sales engineer, Adolf Seitz, it started out as just another day at the office, helping customers with their coil cord and cable assembly needs.

“We’d been working with RJL Systems for years,” explains Seitz, “supplying cable assemblies for their analytical equipment.” Michigan-based RJL is recognized as one of the foremost manufacturers of Bioelectrical Impedance Analysis (BIA) instruments. These instruments are used to measure body composition for medical and research purposes. “But when they called us this time, it was for a very special project. The BIA was going to be used in a research expedition to determine the effects of global warming on polar bear health.”

Bear necessities

For the expedition, the standard BIA needed to be retrofitted to withstand extreme temperatures and repeated flexing and bending. It also needed to be polar bear sized. This meant the cable assembly used as the interface between the instrument and the subject lead on the polar bear would have to be extended from six feet to 10 feet. Electrodes on either end of the cable assembly were going to be attached to the tongue and backside of the animal.

“Adding the extra footage was not as straightforward as it might seem. We also had to make sure the cable could bend repeatedly at the Y-junction and remain flexible without breaking,” says Seitz. “We also needed to change the jacketing over the wire and add strands to it to ensure the wire would hold up as expected with the increased voltage necessary.” A very, very low level of current passes through the wire in the cable to the BIA to determine body mass measurement. When using the BIA with polar bears, it’s critical for the device to work as expected. Instrument failure is not really an option on a polar bear expedition, because there’s no time for do overs.

Seitz worked with RJL to engineer a cable assembly to meet the rigors of the project. In the end polyurethane was used as the outside coating of the cable assembly because it is quite resilient and can withstand an extreme temperature range. Inside Teflon coating was applied as insulation over the stranded wire, and an overmold was fashioned at the Y-junction, so one continuous 10-foot piece of wire could be used. The overmold forms a solid mechanical bond with the cable protecting the wire within against breakage.

Before sending the redesigned cable assembly to RJL for the fieldwork, each unit was thoroughly tested to ensure the current held up through the length of the wire as expected. “Our cable assembly performed admirably on the expedition,” relates Seitz. “Measurements of the bears were collected without any problems.”