1-13. SITE PREPARATION

TM 5-6635-386-12&P If the tester consistently exhibits a tendency towards a low deviation, that is more towards the 0.75 end for the calculator or more towards a 2 out or 1 out for the manual method, then the tester is picking up some periodic count rather than purely random count, tester repair may be required. This smooth tendency is probably due to a failing filter network in some supply system which would allow a steady noise to creep into the system, a noise not subject to the variation of a random source. Using either of these techniques, either calculator or manual evaluation, the operator can maintain a close watch on his tester and can be confident that his field work is accurate without electronic error or decay drift. It is not adequate to merely run the automatic standard count and not run the periodic evaluation. The daily automatic standard count will serve to verify general good operation, but it will also mask minor variations between counts that are indicators of potential tester failure. The standard count in the automatic mode can cover up erratic tendencies such as a noisy detector, or other problems. The tester may appear very normal under such conditions. We must maintain a professional attitude about our equipment and its operation at all times. This means frequent checking of standard count and tester performance. 1-13. SITE PREPARATION Tests will only be as good as the quality of site preparation. The site must be flat, free of voids, with surface irregularities filled with native fines or sand. If transmission is used, the hole must be neat and square to the surface, and protected from puffing or movement during the drilling of the transmission hole or retraction of the drill pin. It is desirable to rotate the tester 900 or more on rocky soils to obtain the largest sample size practicable. This avoids the possibility of a single rock skewing the results. Site Selection CPN advocates statistical testing wherein the average of several test sites is used to accept or disapprove the project. The nuclear tester is much faster than the older, conventional test methods and statistical programs may be employed. Using the CPN Random Selection Cards, (See Appendix J) select five site locations and take one test on each location. Average the sites for a statistically valid evaluation of the project. Each site must be free from major protuberances reasonably smooth, and should be representative of the overall project. Preparation Using the CPN Cast Aluminum Guideplate, smooth the surface, removing large stones or surface debris which would prevent the tester from sitting flat. Any technique of smoothing, pounding, or other flattening will be adequate. It is impossible for the operator to pound the site so hard as to compact the site. He can only flatten down the top 1/16" or so to provide a good surface. Using a sieve, shake some native fines or sands over the site to fill in any remaining air voids to remove possible errors from surface roughness. The tester must rest upon native promontories, however, with only the voids filled in. The tester must not rest upon a "cushion" of filler material. If the test site is asphaltic concrete, (AC), a coffee can "salt shaker" with fine sand may be used to fill in the voids. The tester has a reduced bottom surface to provide the best possible seating under adverse conditions. This facilitates seating the tester on AC where a rubber tired roller has been used. 1-14. SEATING QUALITY EXPERIMENT An experiment can be run to test the required effort 1-12