Downloaded from https://www.everyspec.com MIL-STD-1311D 4.4 A warm-up period shall be provided for both the tube (excluding rectifiers) and test equipment in order to obtain stable operating conditions before proceeding with measurements. 5. Procedures. 5.1 Survey-meter method. 5.1.1 The background radiation shall be verified at the test position for the test exposure period and corrections to the observed data shall be applied as required. 5.1.2 The specified voltage of 4.2 and 4.3 shall be applied and the specified current of 4.2 shall be adjusted on the TUT.
(Rectifiers are generally not tested with forward current.) 5.1.3 The detectors specified for this measurement are normally calibrated to read the radiation level at the center of the detecting chamber. Therefore, the distance from the TUT to the center of the chamber shall be 6 inches. This corresponds to the 4 inches from the external surface of the TUT, to the plastic spacer of the 440 RF/C survey meter. For equivalent equipment with different dimensions, the tube-to-window distance will change. The tube-to-center-of-chamber distance remains constant. The detection device should not be closer than 4 inches at up to 40 kv because of the high-voltage hazard.
Appropriate precautions should be taken to prevent corona which could result in spurious readings. 5.1.4 Radiation measurements shall be made at the location of maximum intensity. This point may be found by rotating the tube or the survey meter. 5.1.5 Readings. At the point of maximum radiation, record the maximum stable radiation observed in mR/hr. During any exposure period the voltage and current shall be constantly monitored to insure conformance with 4.2 and 4.3. The maximum allowable radiation limit in mR/hr shall be specified on the TSS. NOTE: Transient deflections of the survey needle due to unrelated environmental radiation may occur randomly and vary in magnitude.
Before a reading is recorded, precaution should be taken to assure that the indication is a steady one due only to the tube being measured. 6. Precautions. 6.1 X-radiation of the soft x-ray category may constitute a health hazard on a prolonged exposure at close range. Therefore, equipment design shall provide for adequate shielding. Adequate precautions shall be taken to protect personnel from this hazard and film badges or other monitoring devices shall be assigned to all personnel involved in performing x-radiation measurements. 6.2 A warning label informing of these precautions shall be placed in an appropriate position on the equipment. METHOD 2202 2202-2 28 March 1975