Piezoceramic float dust deposition meter: a feasibility study

The US Bureau of Mines is exploring the possibility of designing a meter to measure the quantity of float dust deposited at various locations in a coal-mine by using the change in the resonant frequency of a piezoceramic diaphragm. The results of the study have shown that dust deposited on a 0.9 in diameter, 0.021 in thick piezoceramic diaphragm with a natural frequency of about 2.5 kHz exhibits a linear frequency change of about 1 Hz for every mg/cm/sup 2/ of dust loaded on the diaphragm between 0 mg/cm/sup 2/ and 30 mg/cm/sup 2/ independent of the type of dust used (coal-dust or rock-dust), and 2 Hz/mg-cm/sup -2/ between 30 mg/cm/sup 2/ and 100 mg/cm/sup 2/. The change from 1 Hz/mg-cm/sup -2/ to 2 Hz/mg-cm/sup -2/ at 30 mg/cm/sup 2/ is believed to be associated with a change in the contiguity of the dust deposit. Present results indicate that a float dust deposition meter based on this technology can measure dust loads to within +or-1 mg/cm/sup 2/ but cannot distinguish between coal-dust or rock-dust.<
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