Moisture meter

(Figure) The scheme of the depth moisture meter

MOISTURE METER (EN: moisture meter, moisture tester; DE: Feuchtemesser; FR: hygrometre; ES: medidor de humedad, higrometro; RU: влагомер) is the device for the measurement of the humidity of the gases, liquids, and solid (including loose) bodies. For the measurement of the humidity of the liquids (that is, the content of the admixture of the water within the liquid, for which the water is not the major component, for example, within the petroleum), there are used the capacitive moisture meters, the action of which is based on the determination of the dielectric permeability or of the dielectric losses within the liquid (the dielcometric method), and also the conductometric moisture meter, within which there is measured the electric conductivity of the liquid.

For the determination of the moisture content within the petroleum at the bottomhole of the petroleum boreholes, they use the depth moisture meters, which are lowered into the borehole on the geophysical cable (see the Figure). The action of this instrument is based on the change of the electric capacitance of the frequency transformer; the signal of the instrument is sent through the cable onto the surface, and the deciphering of this signal is performed according to the calibration graph. The maximal measurable value of the moisture content of the petroleum is 50% (in case of the higher moisture content, they use the water meters). In case of the lowering of the instrument into the boreholes with the relatively small yields (with the small speeds of the flow of the liquid), the depth moisture meter is equipped with the remotely controlled packer (for the directing of the liquid through the measuring channel of the instrument), thus the precision is increased.

The humidity of the solid bodies is determined using the capacitive and conductometric moisture meters. They also use the resonant absorption of the radio waves within the ultrahigh frequency range by the nuclei of hydrogen, which belong to the structure of the water. Within such moisture meter, they place the material, which is monitored, into the coil of the oscillatory circuit of the radio-frequency signal generator, the frequency of which they change gradually. At the frequency, which is corresponding to the nuclear magnetic resonance, the absorption of the energy within the oscillatory circuit increases sharply; the value of the energy, which has been absorbed, serves as the measure for the humidity of the material.

They usually determine the humidity of the air using the hygrometers and psychrometers. Within the hygroscopic electrochemical moisture meter, the humidity of the gases is evaluated according to the change of the properties of the electrolyte, which has been poured into the container of the moisture meter.