MIL-PRF-1/1647E
TABLE I. Group A inspection - Continued.
1/ Npm - N850 = ±0.05 Npm maximum.
Npm - N950 = ±0.05 Npm maximum.
Npm - 5,000 cpm nominal at V dc = 900 V dc.
N850 = Count rate at V dc = 850 V.
N950 = Count rate at V dc = 950 V.
2/ Tube count rates shall be determined using a scaler having a maximum pulse pair resolving time of 10 µs and a
pulse height discrimination level of 0.25 volt.
3/ The tube end window shall be exposed to radiation from a General Electric 15-watt germicidal lamp and a
General Electric 15-watt fluorescent lamp, or equivalents. Light sources shall be located not more than 1 inch
(25.4 mm) from the mica window surface (see figure 2).
4/ The criterion for passing this test shall be compliance of at least 80 percent of the tubes, after test, with the
requirements for starting voltage and relative plateau slope.
5/ The counting rate shall be not less than 10 percent below the value of the count rate specified in the EON TC-9
excitation unit, or equivalent (see figure 3).
6/ With the tube in a field giving 100 ±10 Nps at 900 V dc, determine tube response (count rate) at each of the
following temperatures and in the order shown:
(1)
Room temperature
-20°C
(2)
(3)
Room temperature
+55°C
(4)
(5)
Room temperature
A minimum stabilization time of 30 minutes shall be allowed at each temperature. The absolute count rate at 900
V dc shall not differ from the initial readings at room temperature by more than 10 percent at any of the four
subsequent temperatures.
7/ The tube shall be mounted by means of a rigid fixture which clamps the detector at the cathode as shown on
figure 4.
8/ Test shall be made at ambient conditions of normal room temperature and humidity.
9/ This is an alternate test to method 1041. Either method 1041 or method 1042 may be used but only one of these
tests shall be performed.
10/ The manufacturer, with the approval of the qualifying activity, may perform this test on a periodic basis, versus
performing the test on every lot. Approval will be based on demonstrating to the qualifying activity the capability
of the design to meet this requirement. If the design, material construction or processing of the tube is changed
or if there are any quality problems, the qualifying activity may require resumption of the original testing
frequency. This allowance does not relieve the manufacturer from meeting the test requirements in case of
dispute. It is mandatory that the manufacturer shall immediately inform the qualifying activity of any known
changes to the design, material construction or manufacturing processes or of quality problems with the electron
tube. The periodic test cycle approved shall not exceed in duration the current conformance test cycle or two
years, whichever is shorter.
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