Just some thoughts as I've been reading through all the calibration posts. As I understand the "pick one" brand of volumetric system, elevator speed would be just as critical to obtaining an accurate mass flow reading as in an impact type system, if not more so. The elevator speed is important because the only sensing occurring is the length of light vs. dark pulses and in order to translate pulse width into how much grain is sitting on top of the paddle you have to know how fast the paddles are moving (Lexion graphic attached). So in a volumetric system elevator speed is a primary input to estimating mass flow, in an impact type system the elevator speed is used as a secondary input to force in order to compensate for variation in elevator speed and thus grain velocity when calculating mass flow.

I also wonder how fair a comparison is in accuracy when done at a larger level. You would expect the larger the comparison load the more agreement there would be among the systems. Because a volumetric or single point impact (early JD) would be accurate at the average flow rate (or whatever the rate of calibration was), the discrepancies would occur at the upper and lower ends. I think it would be interesting to see these compared at consistent varying flow rates (that isn't written well but, ex. stable test runs of 500 bu/hr, 1000 bu/hr, 1500 bu/hr, 2000 bu/hr) whatever your range is. It would also be interesting to see comparisons in a step flow type of test, the type of test laid out by ASAE X579. Single point calibrations are nice and work well with linear responses, unfortunately, life is complicated and sensor responses to grain flow are generally not linear. Everything's a tradeoff.

I envy those of you with two systems on your combine, would be really interesting and fun to see that data, I have really enjoyed the threads on this, it's been thought provoking and fun to read.

Best Regards,

Lucas Haag

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