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/cm² of dust loaded on the diaphragm between 0 mg/cm² and 30 mg/cm² independent of the type of dust used (coal-dust or rock-dust), and 2 Hz/mg-cm^-2 between 30 mg/cm² and 100 mg/cm ². The change from 1 Hz/mg-cm^-2 to 2 Hz/mg-cm^-2 at 30 mg/cm² 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 ±1 mg/cm² but cannot distinguish between coal-dust or rock-dust