ISSUE FOCUS 48 FEED & ADDITIVE MAGAZINE May 2023 ture sensors after the final installation as any change in the sensor positioning can affect the measurement. The calibration procedure consists of taking samples of the material flow from directly beneath or after the sensor installation whilst recording an average value of the sensor value. The material sample must be tested using a standard moisture laboratory test, and this result matched with that recorded. After obtaining several results, it is possible to define the relationship between them using mathematical techniques. SENSOR TECHNOLOGY Older technology sensors using either resistive, capacitive, or analogue microwave techniques have a non-linear calibration, so a graph of the sensor value against the moisture change has a curve labelled as ‘Older Analogue Technology’ in Figure 2. The non-linear relationship has a more complex mathematical definition. This relationship must be managed either using a highly complex calibration process with many sample results and curve-fitting software or an assumption of linearity, which results in the errors indicated by the shaded area in Figure 2. There is also a maximum point above where the curve flattens, showing that the sensor has a much lower sensitivity and cannot react to any moisture above this point. Figure 2. Hydronix Digital Technology World Leaders in Microwave Moisture Measurement Oil Animal Feed Coff ee Rice Grain Hydro-Probe XT Hoppers, chutes, belt conveyors Hydro-Mix XT-FS Mixers, conveyors, Ducting System Hydro-Mix XT-EX Certified for use in ATEX, IECEx and NEC/CSA Hazardous Locations (Dust) Hydro-Mix HT-EX Mixers, conveyors, Ducting System, High Temperature Non Food-Safe available Non EX available Non EX available enquiries@hydronix.com Contact us for more details hydronix.com
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