Crop Yield Monitor Calibration Tips

Your yield monitor can provide the right information to help you make better seed selection and placement decisions in the year to come. The data can also help identify yield-influencing factors you may not have seen from other field observations. But keep in mind displayed data is based on estimates, and your interpretation is only as good as the quality of your information. Optimizing yield monitor data requires knowledgeable set up and calibration.

How yield monitors estimate yield
The yield monitor system is more than the cab display monitor. It includes several sensors that collect display data in the combine cab. Sensors provide estimates of 3 main data points:

1. Rate of grain flow as measured from the impact plate, or optical sensors
2. Distance traveled using GPS
3. Grain moisture as measured from sensor plate

In addition, operators need to manually enter 3 pieces of data:

1. Lag time
2. Header position
3. Header width

Depending on the type of yield monitor, there may be additional pieces of data used to determine the monitor yield estimate.

Accurately assess yield 
Yield monitors must be calibrated or “trained” to interpret signals to provide more accurate yield estimates. The first step toward properly capturing yield data is to become familiar with the combine monitor system being used and its components. The owner’s manual should outline the specific calibration method for your equipment, but some good general pointers to keep in mind are below.

1. Mass flow impact sensor:
   • This is the most important calibration measurement, as it determines grain flow at pounds per second through the clean grain elevator in the combine.
   • Most yield monitor systems have the ability to add multipoint/load calibration points to allow estimates over different flow ranges.
     Pictured below is an example of a common impact plate sensor, which is located at the top of a combine’s clean grain elevator. 
      
2. Mass flow vibration calibration impact sensor plate:
   • This calibration is used to document the vibration effect when the combine is running. 
   • To ensure you’re measuring correctly, confirm the proper header is attached and in operating position instead of resting on the ground, the combine is empty of grain, the separator and header are engaged and the combine is running at full revolutions per minute (RPM).
3. Moisture sensor calibration performed prior to weight calibration:
   • Using a handheld moisture tester, calibrate sensor output from the grain tank to multiple in-field samples per calibration load. 
   • Moisture sensors will adequately measure grain moisture in the 10 to 33% range.
     Below is an example of a moisture sensor, which is typically located on the combine’s grain elevator for easy access to clean blades.
     
4. Temperature calibration performed before weight calibration:
   • Helps ensure mass flow sensor and moisture sensors are interpreting correctly.
5. Lag time settings:
   • Measurement of time it takes grain to travel from the header to the mass flow sensor.
   • Compensation for grain flow delay allows more accurate yield mapping.
   • Total time typically ranges between 10-15 seconds: however subtracting 1-2 seconds from total measured time should remove the time grain travels from the mass flow sensor to entering the bin.
6. Header position setting controls when yield data should and shouldn’t be recorded:
   • Proper settings ensure false yield data is not being recorded while no crop is being harvested, such as when turning at the end of the row. 
7. GPS measurements of harvest speed and distance:
   • Abrupt speed changes commonly cause yield estimate errors, which are difficult to fix with calibration, but can be corrected post-harvest with data analytics.
8. Header cut width setting according to number of rows by row spacing:
   • Another common problem is having an incorrect harvest width or partial header setting. 
   • If header width changes mid-season, weight calibrations should be performed again.

Quick Calibration Tips
When calibrating yield monitors, pay extra attention to details. Combine and yield monitor user guides are great references to help create a yield monitor checklist of adjustments to make before harvest. Now that you’re more familiar with the yield calibration components, here are 7 additional quick calibration tips to help you start testing:

1. Harvest and calibrate using a wide range of hybrids with different grain moisture.
2. Harvest a minimum of 3,000 lbs. per calibration load.
3. Use minimum of 4-8 calibration loads to properly measure.
4. Harvest each calibration load at different load rates, such as combine harvest speeds at 3, 4, 5 and 6 mph per load.
5. Calibrate separately for each crop you plan to harvest. 
6. Make sure the weigh wagon or grain catch cart scales used for calibration are accurate.
7. Do not unload on the go while calibrating.

Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.

References:

• University of Nebraska Extension Publication EC2004: https://extensionpublications.unl.edu/assets/pdf/ec2004.pdf
• Purdue University Extension: https://www.agry.purdue.edu/ext/corn/news/timeless/yldmoncalibr.html
• The Ohio State University ANR-8: https://ohioline.osu.edu/factsheet/anr-8
• Michigan State University Extension: https://msue.anr.msu.edu/news/yield_monitor_calibration_procedure

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