1、F - 7 6 A -.I“ EIA TEP167 70 3234600 0008470 O m - SEPTEMBER 1970 RECOMMENDED PRACTICE FOR MEASUREMENT OF X-RADIATION FROM RECEIVING TUBES FORMULATEQ BY JEDEC ELECTRON TUBE COUNCIL JEQEC PUBLICATION NO. 67A =-, . L_h_ PRICE $1.00 EIA TEP167 70 m 3234600 0008471 2 m I c ELECTRONIC . RiblW by INDUSTRI
2、ES ASSOCIATION 4 such as Geiger-Mueller counters, proportional counters, scin- tiilation counters, or solid-state counters, provided that the calibration is known over the energy ranges being meas- ured and differences in cross-sectional areas of the detec- tors are considered. 2.2 Test Equipment -
3、To provide stable electronic conditions for opera- tion of the tube under test and to measure anode voltage and current. Note: Test equipment shall be so designed as to shield operators to well below acceptable personnel safetylefrel, 2.2.1 High Voltage Meter - A meter for measurement of the high vo
4、ltage during test, with an accuracy of at least f 0.5%. a high-voltage divider with suitable accuracy and stability. Current Meter - A meter for measurement of the current during test, .with an accuracy of at least f 2.0%. Calibrate using 2.2.2 2.3 Survey Meter Support - A holder for supporting the
5、survey meter dur- ing exposure in the recommended positions. It shall be constructed of wood or plastic and shall not lie between the meter and the tube. 3. Calibration 3.1 The survey meter shall be calibrated by exposure to an x-ray field of such an energy that the half-value layer of aluminum is 1
6、.1 mm. This results in an effective energy of about 23 keV. The calibrating -2- , .L. 1 EIA TEPL67 70 = 3234600 0008474 8 dose rate shall be representative of the intensities to be measured This calibration shall be made traceable to the National Bureau of Standards. Note 1: To insure accurate instr
7、umentation, consideration should be given to correction factors for extreme variations in temperature and barometric pressure. If two or more individual laboratories require comparative . radiation measurements, it is suggested that all survey meters be calibrated by using a common standard and by o
8、ne standards laboratory (Victoreen Instrument Division, or equivalent). Note 2: 3.2 Stability of the calibration may be checked periodically by using an appropriate radioactive source. 4. Test Conditions 4.1 The tube under test shall be positioned relative to the test equipment so that measurements
9、will be made at the point where maximum radiation is observed, Shunt Regulators - The tube undertest shall be operated at the maxi- mum rated h.igh dc plate (not supply) voltage and current, which shall not vary or drift, including ripple, more than f 0.5% during the en- tire test period. If the com
10、bination of maximum rated high dc plate voltage and current produces a dissipation value in excess of the tube types maximum plate dissipation rating, the current shall be reduced by an amount such that the maximum rated plate dissipation value is acquired without reduction of the rated dc plate vol
11、tage, 4.2 O 4.3 High Voltage Rectifiers - These tubes shall be tested under dc condi- tions. voltage (total dc and peak), will be applied to the cathode or filament. This voltage shall not vary or drift, including ripple, more than f 0.5% during the entire test period. It is not necessary to energiz
12、e the heater or filament during this test. The power supply impedance should be a minimum of three megohms to prevent arcing which can influence the radiation reading. A dc potential, corresponding to the maximum-rated peak inverse 4.4 A warm-up period shall be provided for both the tube (excluding
13、recti- fiers) and test equipment in order to obtain stable operating condi- tions 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 b
14、e applied as required. -3- 6. EIA TEP167 70 M 3234600 O008475 T M t d 5.1.2 The apecified voltages of Sections 4,2 and 4.3 shall be applied and the specified current of Section 4.2 shall be adjuste on the . tube under test, (Rectifiers are generally not tested with for- ward current . ) 5.1.3 The de
15、tectors specified for this measurement are normally Cali- brated to read the radiation level at the center of the detecting chamber. Therefore, the distance from the tube under test to the center of the chamber shall be six (6) inches. This corresponds to the four (4) inches from the external surfac
16、e-of the tube un- der test, 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 dis- tance remains constant. than four (4) inches at up to 40 kV because of the high voltage haz
17、ard. which could result in spurious readings. Radiation measurements shall be made at the location of maximum intensity. This point may be found by rotating the tube or the survey meter . Readings - At the Roint of maximum radlation, record the maximum stable radiation observed in mR/h. the voltage
18、and current shall be constantly monitored to insure conformance with Sections 4.2 and 4.3. The detection device should not be closer Appropriate precautions should be taken to prevent corona 5,1,4 5.1.5 During any exposure period Note: Transient deflections of the survey meter needle due to . unrela
19、ted environmental radiation may occur randomly and vary in magnitude. Before a reading is recorded, precau- tion should be taken to assure that the indication is a steady one due only to the tube being measured, c Recorded Information The recorded fnformation shall contain the following: 6.1 . Ident
20、ification of the tube specimen. 6.2 Test date, laboratory, and pertinent information on test equipment, including model and serial numbers of survey meters, 6.3 Anode voltage and current, and any other test equipment data neces-. sary to interpret results. Report of readings per Section 5.1.5. 6.4 65 Position of radiation measuring device.
