Skip to main content
ARS Home » Plains Area » Lubbock, Texas » Cropping Systems Research Laboratory » Cotton Production and Processing Research » Research » Publications at this Location » Publication #243688
Title: Low-cost electronic microwave calibration for rapid on-line moisture sensing of seedcotton

Author
item Pelletier, Mathew
item VIERA, JOSEPH - Microsemi

Submitted to: Sensors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2010
Publication Date: 12/6/2010
Citation: Pelletier, M.G., Viera, J.A. 2010. Low-cost electronic microwave calibration for rapid on-line moisture sensing of seedcotton. Sensors. 10(12):11088-11099.

Interpretive Summary: For rapid on-line moisture sensing of seedcotton in cotton gins of critical need is a means by which to establish a reliable wide-band electronic calibration by which to center the circuit due to changes in the internal signal delays and attenuations caused by temperature changes to the various system components and circuit elements. This research examines a hardware technique for use in conjunction with microwave reflective sensing probes with an extended bandwidth from 500MHz through 2.5GHz. Comparison testing of the new technique was performed and validated experimentally against known electrical propagation delay standards. Results of the measured propagation delay with this type of automatic electronic calibration method was found to sustain the accuracy of the measurement to within 4% of the measurement, 95% confidence with a standard error of +/-18.6 pico-seconds for the delay measurements.

Technical Abstract: In order to improve rapid on-line moisture sensing of seedcotton in cotton gins, a means by which to establish a reliable wide-band electronic calibration is critically needed. This calibration is needed to center the circuit due to changes in the internal signal delays and attenuations caused by temperature changes in the various system components and circuit elements. A limitation on this calibration procedure is the inability to physically remove the circuit from the on-line system to periodically calibrate it. This research examines a hardware technique for use in conjunction with microwave reflective sensing probes having an extended bandwidth from 500MHz through 2.5GHz. This new technique was validated experimentally against known electrical propagation delay standards. Results of the measured propagation delay with this type of automatic electronic calibration method was found to agree with results using a normal vector network analyzer with a traditional 6 term S11 single port error correction calibration methodology to within 4% of the measurement, 95% confidence, with a standard error of +/-18.6 ps for the delay measurements. At this level of performance, the proposed technique exhibits superior performance over the typical field time-domain reflectometer (TDR) instruments in common use in soil moisture testing and is likely sufficient for use in cotton gin moisture sensing of seedcotton.