1-4. PANEL CONTROLS

TM 5-6635-386-12&P object of the same mass will produce a major loss of energy or slowing down. The only atom which can markedly slow down a fast neutron, and which we would likely see in soil, IS hydrogen. The hydrogen nucleus is the same mass as the neutron and slows down the neutron Immensely compared to collisions with other nuclei. The greatest loss of energy in any collision is when two similar mass objects collide. A simple analogy is that of a golf ball colliding with a bowling ball. The golf ball would rebound with little loss of energy. The golf ball colliding with BB’s (electrons floating around a nucleus) would push them aside. However, two golf balls colliding would produce a strong loss of energy in each of them, or a transfer of energy from one to the other. This is what happens when a fast neutron hits a hydrogen atom. The neutron is markedly slowed down. A few collisions with hydrogen atoms reduces a fast neutron to the slow or "thermal" energy at which the moisture detectors in the soil tester can "see" the slow neutron. Thus, the moisture channel is in reality a "Hydrogen Analyzer" and is responsive to any form of hydrogen present whether it be in the form of water, or of some organic matter. It is possible to measure water on a construction site because the only form of hydrogen we normally see on a soil site is free water, the very feature we are trying to measure. However, bound water within the mineral matrix, organic matter, roots, or asphalt in an asphalt pavement would also provide hydrogen moderation and the neutron tester would "read" it accordingly. If we know the quantity of extraneous hydrogen, we can account for it in calibration and the tester can still be used for moisture determination. Neutron radiation is emitted by any alpha producing source when mixed with Beryllium. CPN uses Americium/Beryllium (AmBe) source in its soil testers. 1-4. PANEL CONTROLS Refer to Keyboard (Fig. 1-1) - Each Touchkey is outlined below. CLEAR = Stops count in progress. Stores this count and does not reset the display to zero. Cancels any other prior program keys (D or M-ONLY). Pushing a display touchkey will produce a display of the stored count. Note that the tester will go through its normal, rapid shutdown "beep" to alert the operator that the tester was stopped deliberately and not automatically. LOCK = Interlocks TEST and STANDARD to prevent accidental field actuation of either o’ these two functions. LOCK by itself will do nothing. STD = When pressed simultaneously with LOCK, will erase all four memories and will initiate a 4 Minute count into all four memories. This provides a check on the performance of the memories. The stored readings are normalized to the 1/4 minute time base for ease of operator computation. STD by itself will do nothing. The two STANDARD memories will be retained for future recall. Pushing any of the 4 OPERATION buttons will erase the standard count stored in the D-DATA and M- DATA memories and they will count normally. TEST = When pressed with any DISPLAY key, will light all 8’s to test the display and the display command system. When pressed alone, it displays a random number which should be discarded. 1-4