Development of a portable grain mass flow sensor test rig

Abstract

A portable grain mass flow sensor test rig was built to measure the accuracy of a mass flow sensor with dual use in the field as well as in the lab. Concurrently, a synchronization method was developed that employs GPS timing data to synchronize the mass flow sensor data with the reference scale data. Two-point calibration was compared to multi-point calibration under steady-state flow. These tests on mass flow rate of corn with no variation in ground slope indicated that a multi-point calibration is preferable to a two-point calibration, confirming the results of previous research. The results indicated that the accuracy of the mass flow sensor is very good ( R 2 = 0.99) if it is run about the specific flow rate for which it was calibrated. Errors up to 8.2% occurred at lower flow rates when the system had been calibrated only at zero and the maximum flow rate. The effect of slope on accuracy of the mass flow sensor was investigated by inclining the clean grain elevator in two planes simulating pitch and roll. A roll of 5° (sideways) did not alter the mass flow sensor zero-point calibration and showed no significant effect on accuracy of the mass flow sensor. At 10° pitch, the calibration was altered and significantly affected the accuracy of the mass flow sensor, especially at lower grain flow rates. Ground slope could have an adverse effect on mass flow sensor accuracy; however, the mass flow sensor can perform well when calibrated for a given slope. The results with a relatively small test rig verify the concept, and show that a larger rig could accurately simulate field conditions for mass flow sensors on the biggest combines available.