MIL-PRF-49446B(CR)
on the label as shown in View K of 5004385. Data shall be marked in contrasting characters on a
background in accordance with Note 27 of 5004385. The Detector-Dewar shall consist of a 60-
element detector array and a resistor bias pack.
3.5 Performance characteristics.
3.5.1 Detector-Dewar defects. Detector-Dewar shall operate 80 , +5/ -20 K. The
Detector-Dewar shall contain no more than two (2) defective elements. Elements 85-96 shall be
defect free. Defects shall be separated from one another by at least four (4) nondefective
elements. Elements that are open (dead) or have a D*BB of less than 5.0 x 109 shall be
electrically strapped to an adjacent element with common ground. Perform 4.5.1 for acceptance.
3.5.2 Time constant. The time constant is the time for the element response to reach
63% of its steady state value when irradiated by a 7.5-12 micrometer source producing a signal to
noise ratio of <100:1. The time constant of each detector element shall be less than two (2)
microseconds. Perform 4.5.2 for acceptance.
3.5.3 Sensitive area. The physical area shall be 0.0960 by 0.07440 inch or greater as
determined by an optical microscope or similar method. Perform 4.5.3 for acceptance.
3.5.4 Crosstalk. The Crosstalk signal level between any two (2) elements shall be less
than -26 dB as determined by measuring 4 elements. Perform 4.5.4 for acceptance.
3.5.5 Blackbody detectivity. The Blackbody detectivity of all nondefective elements
shall be at least 7.5 x 109 an Hz 1/2 w-1 except for channels 85-96 which shall not be less than 9.0
x109 cm Hz1/2 w-1 when the Dewar is cooled with LN2 to 77 ± 3 K. Perform 4.5.5 for
acceptance.
3.5.6 Noise. The detector noise of each element shall be at least 2.5x10-9 volts RMS
Hz1/2. Perform 4.5.6 for acceptance.
3.5.7 Responsivity. The average 500 K blackbody responsivities of the acceptable
elements shall not be less than 8.3 x 103 volts/watt, nor greater than 20 x10 3 volts/watt, when
the Dewar is cooled with LN2 to 77o, ±3 K. The blackbody responsivity of each element shall
not vary by more than ±20 percent of the mean value of the elements which are not defective (see
6.4.2). The nominal detector element size shall be used in responsivity calculations and
blackbody temperature shall be 500 , ±5 K (see 6.3.7). Perform 4.5.7 for acceptance.
3.5.8 Temperature sensors. Temperature sensors shall be installed at or near the detector
array location in the Dewar to provide an electrical signal which is an analog of temperature.
The temperature sensor shall have a junction voltage of 1.060, 0.015 volts with a 1.00 mA,
0.01 mA forward current when the Detector-Dewar is operated at 77 , ±3 K. The voltage
shall be recorded on the appropriate label on the Detector. Perform 4.5.8 for acceptance.
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