One of the quality indicators of the produced mining and chemical raw materials and processed products is their moisture content. Reliable control of humidity requires a lot of labor and time.

At Apatit, apatite ore is delivered from the mines to the concentrators by railroad dump trucks with a capacity of 100 tons. Loading of dumpcars is carried out by a hatch worker from the ore mines or bunkers of loading stations ...

To control the composition of substances, their molecular state, moisture content of various materials in measurement technology is widely used dependence of dielectric permittivity value on these parameters. In this case the change of dielectric permittivity of the substance filling the measuring capacitor, which is the primary measuring transducer, leads to a change in its initial electrical capacitance ...

In discrete rapid monitoring of the moisture content of dispersed materials, devices based on the E12-1A instrument, whose simplified circuit is shown in Figure 1, are in some cases used. The range and accuracy of moisture measurements of materials are determined not only by the design of the sensor, but also by the circuit of the measuring oscillator. The range of moisture measurement can also be extended and the effect of losses reduced by increasing the overall gain of the stage, for example, by replacing the cathode follower with an aperiodic amplifier with an anode load.

Numerous methods of measuring the moisture content of solid, liquid and bulk materials are known: conductometric, based on the use of the relationship between moisture and the active resistance of the material; capacitive – between moisture and dielectric permittivity (more precisely – apparent capacitance); neutron; nuclear magnetic resonance – NMR, etc.

At present, either electrical resistance (conductivity) or capacitance value is used as an output parameter of electrode sensors used in mineral processing. On the basis of theoretical studies by E. S. Krichevsky and A. I. Nudelman (Leningrad Mining Institute) it is possible to create special circuits that allow transforming the value of resistance or capacitance in electrode sensing devices into the phase angle between the current in the measuring circuit and the voltage supplying this device.