The following commentary does not necessarily reflect the views of AgWeb or Farm Journal Media. The opinions expressed below are the author's own.
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The following commentary does not necessarily reflect the views of AgWeb or Farm Journal Media. The opinions expressed below are the author's own.
As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Along with his In the Shop blog, Dan writes a column by the same name as well as the Shop Series for Farm Journal magazine. Always providing practical information, he is a master at tackling technical topics and making them easy for all of our readers to understand. He and his wife, Becky, live near Bouton, Iowa.
The newer a piece of farm equipment, the more likely some aspect of it needs to be calibrated, and sometimes re-calibrated, for it to work correctly. In case. you've ever wondered, here's what calibration accomplishes.
Many calibrations involve a potentiometer. A potentiometer is an electrical device connected to machinery in a way that when the machinery moves up, down or sideways, an arm or linkage transfers that movement to the potentiometer. The potentiometer has specified voltage going into it, and variable voltage coming out of it. The movement of the potentiometer's arm varies the output voltage. If a particular potentiometer has 12 volts going into it, moving its sensing arm through its full range of motion could change output voltage from, say, 1.3 volts to 10.5 volts.
The cool thing about potentiometers is that if you hook a potentiometer to a computer, you can have the computer react to the change in voltage. As in, on a soybean platform height control system, you can have the computer raise or lower the header depending on the voltage coming from the header height potentiometer.
Calibrating such a system is simply the process of teaching the computer how much voltage the potentiometer will output across the range of movement of the head. That's why during automatic header height control system calibration either the operator or the automated system raises the head all the way up, then drops it all the way down, so the computer can "learn" the highest, lowest and all the in-between voltages the system will deal with during field operation.
The importance of calibrating such a system is two-fold: the system CAN'T work until initial parameters are established, and WON'T work correctly if the parameters are altered. That's why automatic header height control systems, or chaffer/sieve adjusting systems, or other calibrated systems on combines sometimes quit working or don't work right. Ram the header into the ground, tweak a control linkage, and the attached potentiometer suddenly puts out too much, too little or no voltage at all, leaving the computer confused about what it's supposed to do. So it shuts off the hydraulics and throws an error code.
If a bunch of cobs get wedged in the chaffer and the operator leans on the "chaffer close" button in the cab, the linkages to that system (or the actual chaffer louvers) get bent. The chaffer readout in the cab may show the chaffer is nearly closed, but in reality it's twisted nearly wide open.
My point in this overlong explanation is that any system on a combine that has the opportunity to be calibrated should be calibrated before harvest, and re-calibrated as needed during harvest. You will see this material again in the next few weeks, because I'm going to do several blogs on mis-calibrations and other situations that can lead to poor combine performance and/or expensive repairs.
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