1-5. SOURCE ACTUATION

TM 5-6635-386-12&P WARNING Insure that the tester handle is placed in the safe position prior to placing the tester into the approved carrying case. Upon completion of testing, remove battery pack and store in storage case separately from tester. There is no ON/OFF switch and today’s last readings will still be available when the tester is used next. 1-5. SOURCE ACTUATION The shutter is released by pulling back on the handle latch pin and pressing down on the handle. The shutter is spring loaded and closes automatically when the handle is raised to the SAFE position. The operator should insure proper latch or handle position by visually checking the latch pin for full forward location at the desired depth. Lock the source rod when in storage by pushing in the lock button on the end of the rod. Key required to unlock handle. After repeated tests the shutter mechanism will become dirty with accumulated soil pulled into the chamber on the end of the source rod. The shutter will jam or become sticky. See Para 3-6 for shutter maintenance. Do not force the source rod to open the shutter. 1-6.TO MEASURE OR TAKE A TEST, GENERAL The following operations are required to take a field test: a. Take a Standard Count. b. Prepare the Site. c. Take a Reading on the Site. d. Determine Moisture and Density from the Charts. e. Compute Percent Compaction. WARNING Insure that the tester handle is placed In the safe position prior to placing the tester into the approved carrying case f. Store the Tester Away. 1-7. STANDARD COUNT Nuclear tester performance is affected by the decay of the radioactive source, by aging of the electronic components, and by minor mechanical wear and tear. As with any measurement tool, it is necessary to check the tester against a reference standard periodically to insure continued accurate operation. This is achieved with your tester by the taking of a Standard Count on the reference standard furnished with the tester. Variations in tester performance will affect the Standard Count in the same proportion as they will affect the field counts. Should variations in tester performance occur, these variations will affect both the field and standard counts proportionately, thus the final ratio remains constant and the tester remains accurate. The standard count thus becomes a means of continual calibration correction for the nuclear tester. A further benefit can be achieved from the standard count due to the statistically reliable nature of the decay of the radioactive source over short periods of counting. The following paragraphs describe methods of evaluating tester performance using inspection of a series of successive counts in a standard count series. 1-8. HOW TO TAKE A STANDARD COUNT Manual and automatic are two methods of taking a standard count. Both use the same mechanical setup. They differ only in the method of accumulating the final count results. 1-8