Tending to Grain Bin Sensors

Despite the best-laid plans, things do go wrong with grain bin cables and monitoring systems, warns Heath Roker.

Roker should know. He's at the front line of handling problems that can occur with bin cables as the sales engineer for Kasa Controls. The Salina, Kansas-based firm supplies equipment for load-out systems, bulk material handling, and a host of electronic systems for grain storage.

"Over time, temperature cables, just like any other components of farm equipment, will quit working," Roker explains. "Then, there are cables that can work without a problem for 20 years or more, but over time, they become inaccurate. So much so, that when new replacement cables are installed, suddenly you are getting big differences in the temperature readings."

Thermocoupler cable challenges
Early grain bin temperature monitoring systems employed older-style thermocouple cables. Such cables represent 1950s analog technology, Roker explains. Unfortunately, thermocouple cables lose accuracy over time. They are analog (as opposed to digital) and, thus, are slower to read with modern handheld meters.

Broken connections and broken cables are also more likely with thermocouple cables.

"There are often two connections in the cable for every temperature sensor," Roker explains. "When thermocouple cables are in use in taller bins, the cables are under more strain, which takes a toll over time. When you're pulling grain out of the bottom of a large bin, the weight of that grain is drawing down on the cable. In tall bins, you can have as much as 10,000 pounds of pull on some of those cables. Generally, you won't have a problem because an integrator will spec the cables for the job. Regardless of how well the system was spec'd, this strain has an effect over time, causing the cables and related system to lose accuracy."

Another challenge with older bin temperature monitoring systems is that the "analog cables may have 18 to 22 sensors or nodes," Roker says. "So you have to cycle through each one of those sensors and write down the temperature. You stand there a couple minutes while it cycles at each bin."

If your reader employs a logger, "then you can take the data back to a computer and pull those values up in Excel," Roker says. "The readings are accurate, but it's a snapshot in time, and you need to remember to do it. Temperatures in bins don't change fast, but it's good to see a trend and to be aware if an issue is developing."

Sensor cables today are digital
The state-of-the-art in bin cords today are the digital cables provided by suppliers such as MiFarm.Ag, NAB Automation, OPI-Integris, and TempuTech.

Roker points out that bins are much larger today than a generation ago.

The need for more precise and instant grain temperature readings in such large bins is more crucial.

He recommends that any grain bin temperature monitoring system being installed in new grain bins as well as replacement in older bins consist of digital cables. Digital cables require a special digital interface to read their sensors, he warns.