Abstract

A system for sensing depth of penetration of a dynamic penetrometer was developed. It contained an ultrasonic
distance sensor working together with a microcontroller capable of sensing and recording distance of penetration
and field data necessary for the construction of the penetration resistance (PR) profile. The system was equipped
to the conventional dynamic penetrometer of the Department of Soil Science, Kasetsart University at
Kampangsan. The depth sensing system was found to work properly. Depth validation by means of t-test yielded
t value of 0.1713 as compared to 0.9800 of t-table under two-tailed test. In addition the RMSE and the MAPE
values were 1.2625 and 3.3473 %, respectively. Validation test on depth of penetration showed satisfactorily
insignificant difference between depths read by the invented device and by standard measurement. A computer
program for manipulating field data for PR calculation was constructed. The program was written in Microsoft
Visual Basic and imbedded into Microsoft Excel spreadsheet capable of accessing the field data being recorded
in an SD card of the ultrasonic distance sensing system. The data was manipulated by means of a user interface
that enabled the user to construct the PR profile with ease.

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