UBC Theses and Dissertations

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UBC Theses and Dissertations

The design, construction and tests of an in situ capacitance moisture sensor and a portable capacitance moisture meter for organic soil and sawdust Kra, Eric Y.


A capacitance chamber was constructed to measure the capacitance and hence the moisture content of a sawdust sample placed within it. Five readings of capacitance were taken for each sawdust moisture content level. The readings varied widely for each moisture content level suggesting some conditioning of the sample will be necessary if this type of chamber is used as an accurate alternative to the gravimetric oven method of moisture content determination. A simple in situ capacitance moisture meter was also designed and constructed. The device consisted of a 2.0 x3.0 xO.6 cm sensor and a hand-held digital multimeter with a capacitance range. The sensitivity of this moisture meter was compared to that of a commercially available fibreglass resistance type. In a series of experiments, two sensors (one of the capacitance type and one of the fiberglass resistance type) were installed in a different saturated soil and sawdust samples and the readings of the meters and weights of the samples were recorded at regular intervals. Of the two moisture meters, the capacitance moisture meter was found to be more sensitive to small changes in moisture content. With a few modifications (discussed in Chapter 5) to the sensor design, to improve accuracy, it is possible to monitor small changes in small volumes of organic soil and sawdust with this simple in situ capacitance moisture meter.

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