Yield monitors have become a critical management tool on many farms, but they can be nothing more than a $10,000 piece of junk if not maintained. When yield monitors are not calibrated properly, at the end of the day you have nothing more than a digital coloring book of your fields. Without calibration, I could give my nephews a box of crayons and field outlines, and end up with the same thing. Data from uncalibrated yield monitors can haunt us for many years, leading to improper management decisions with long-lasting financial implications.

Prior to harvest

Before harvest starts, there are a few important items to consider. Be sure that last year’s data are backed up; ideally, a copy should be saved separate from the yield monitor logging card. Be sure to label it with the year and yield data. Delete old files to make sure your memory card will not get full during harvest. Check all yield monitor components for wear— the mass flow-impact sensor plate can wear due to grain impact. Check elevator chain paddles for wear. If some paddles are worn more than others, they will throw the grain differently. Make sure the sensors are clean and do not have debris behind or around them.

Mass flow sensor vibrations

During operation, the many moving parts on your combine cause many different vibrations. Even changing headers can change the vibration effects that the mass flow sensor experiences. To conduct this calibration, the thresher and header should be both engaged. The header should be in the air and the combine empty.

Temperature calibration

This calibration is critical but simple for the moisture sensor to accurately estimate grain moisture. This calibration should be done after the combine has been sitting for a few hours in the shade. Using an accurate thermometer, correct the sensor reading to the current ambient temperature. Some displays require you to enter the difference between sensor temperature and ambient temperature.

Header on-off switch, ground speed

Many missing data points and bad data are created by the header switch not stopping or starting data logging. The most common time this calibration causes issues is when you switch from corn to soybeans. The header runs at different heights, and often, the height at which you run your corn head should shut the data logging off, if you were harvesting soybeans.

Most yield monitors use GPS ground speed, so this is less critical today. Still, ground speed  should be checked, especially if a different display or receiver is installed.

Mass flow sensor (weight) calibration

Proper calibration of the mass flow sensor is crucial to the accuracy of the grain flow estimates, and ultimately, the yield calibration. Mass flow calibration should be conducted multiple times each season, conducted in high- and low-moisture grain, and when changing grain characteristics. Harvest calibration loads at different flow rates (low to high). The goal is to have each load harvested at a constant and consistent flow rate. Target flow rates can be achieved by harvesting each load with a full header at different speeds, or harvesting each load at a constant speed with different harvest-swath widths.

Moisture sensor calibration

Moisture sensor calibration should be monitored throughout the season. Recalibrate when errors between the elevator moisture reading and your monitor are found. This is not a true calibration, since only a small amount of grain in the truck is checked and may not be the same grain your combine sampled. Moisture is a critical component of accurate yields.

It is wise to preform periodic calibration loads throughout a lengthy harvest season to check or improve accuracy of the weight estimates. It is suggested to recalibrate if you observe more than a 5% difference in weight calibration errors, a 5-pound-per-bushel change in grain test weight, or when average daily temperatures change by more than 10 degrees F. You will also need to recalibrate if you change or adjust any part of the yield monitoring system, including tightening the clean grain elevator chain. Be sure to check your data during harvest to make sure they are backing up to the cloud or saving on your memory device properly.

This column is adapted from articles written by Ohio State University’s John Fulton, a professor in research, Extension and teaching; and OSU’s Elizabeth Hawkins, a field specialist in agronomic systems. For more tips on yield monitor calibration, visit this OSU fact sheet.

Hartschuh is a certified crop adviser and an OSU Extension educator. Email him at [email protected].