Correct Answer - Option 4 : Electrical meter method
Concept:
Electrical meter method:
The electrical moisture method is a secondary method for measuring moisture and is best employed if test time is crucial as it offers an instant moisture reading. It’s also a desirable method if contact with the product is acceptable, the accuracy of the highest order is not essential, and where cost is a major factor in the decision. The electrical moisture method is most often used to measure moisture levels of grain and seed, wood, flooring, concrete, and in some other agricultural applications.
Calcium carbide method:
It is a very quick method, it takes only 5-7 minutes. In this method, A standard weight of moist soil sample 5gm is placed in moisture testing equipment and calcium carbide(CaC2) powder is added and the sample is shaken, as a result of the reaction acetylene gas(C2H2) is release. It exerts pressure and pressure is read by the calibrated scale which is converted into water content. This test is done as per IS 2720 (Part II) – 1973.
Oven dry method:
In this method, The soil is heated in a temperature-controlled oven. For inorganic soil temperature maintained is 105-1100C, for organic soil temperature maintained is 600C and if the soil contains calcium compound and gypsum then the temperature maintained is 800. Usually, 4-6 hours for sand and 16-20 hours for clays are required to dry but 24 hours of heating is provided for all types of soil.
\({\bf{moisture}}{\rm{ }}{\bf\ {content}} = \frac{{{{\bf{W}}_2} - {{\bf{W}}_3}}}{{{{\bf{W}}_3} - {{\bf{W}}_1}}}\)
Where,
W1 = weight of the empty container
W2 = weight of the (empty container + moist soil)
W3 = weight of the (empty container + dry soil)