1、?41L-A-25719B (USAF)9 February 1990SUPERSEDINGMIL-A-25719A (USAF)8 Magnetic effect. -With the accelerometer revolved about a magneticcompass with a magnetic field intensity of 0.17 to 0.19 oersted, the compassshall not deflect more than 1.m. Mounting lugs. -The mounting lugs shall withstand a load o
2、f 175 poundswithout fracture.n. Response. -Response characteristics shall be within the Ii.mitsspecifiedin 4.4.5, when the accelerometer is vibrated at frequencies from 1 to 20 hzat maximum g forces for each test point.3.5.1 Accelerometer constructed. The accelerometer shall be so constructed as tow
3、ithstand the normal strains, .iars,vibrations, and such other conditions as areincident to shipping, storage, installation, and service, without failure.a. Pivots, bearings, and gears shall neither bind nor shake and shall he asnear frictionless as practicable.3.6 Part numbering of interchangeable p
4、arts. All parts having the samemanufacturers part number shall be functionally and dimensionally interchangeabThe item identification and part number requirements of MIL-STD-1OO shall governmanufacturers part numbers and changes thereto.3.7 Dial. The dial shall conform to figure 2 and shall be faste
5、ned securely toe.thethecase or upon the frame of the mechanism by not less than two screws in such a mannerthat it will not loosen or turn when the instrument is vibrated. L3.7.1 Distance from dial to cover glass. Distance between dial and cover glassshall not be greater than 0.250 inch.3.7.2 Numera
6、ls and letters. The style and proportion of numerals and letters,except the letter “g”, placed on the dial of the accelerometer shall conform toMS33558. Numerals shall distinctly fndicate graduation to which each applies.3.8 Pointers. The accelerometer shall have three pointers. One main pointer for
7、indicating instantaneous acceleration and two auxiliary pointers: one for indicating6Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I*9375 rllriMIL-A-25719B(USAF)RN)350 R r-q9375.FIGURE 2. Dial and pointer.7Provided by IHSNot for ResaleNo reproducti
8、on or networking permitted without license from IHS-,-,-MIL-A-25719B (USAF)maximum positive acceleration; and one for indicating maximum negative acceleration.The pointers shall conform to figure 2. They shall be light and sufficiently rigidto prevent oscillation under vibration. They shall be firml
9、y attached to themechanism, yet shall be readily adjustable.3.8.1 ,Ratchet mechanism. Each auxiliary pointer shall be provided with a ratchetdevice, in order that indication of maximum plus and minus deflections of the mainpointer will be maintained until the auxiliary pointers are reset to obtain a
10、 newreading.3.8.2 Auxiliary pointer return mechanism% A mechanism shall be provided forresetting the auxiliary pointers into juxta-position with the main pointer. A knob,located as shown on figure 1, shall be provided for operating the return mechanism.Stops shall be provided in order that the auxil
11、iary pointers when reset shall notindicate a lower or higher reading than that indicated by the main pointer. Stopsshall be a part of the mechanism connecting the pointers and shall directly engagethem. Operation of the return mechanism shall require 2.50 to 8 pounds of force onthe knob.3.8.3 Main p
12、ointer mechanism. The main pointer mechanism shall not engage themechanism ofthe auxiliary pointers when the imposed acceleration is less than -theacceleration indicated by the auxiliar pointers.3.9 Acceleration-responsive element.3.9.1 Stops for acceleration-responsive element. Mechanical stops sha
13、ll beprovided for arresting the motion of the acceleration-responsive element when theaccelerometer is subjected to accelerations beyond the limits specified. One stopshall engage .the element at an acceleration of not less than -2.1 g and not morethan-2.2 grand the other at an acceleration of not l
14、ess than +4.1 g and not more?han +4.2 g.3.9.2 Locking device. A device for manually locking the position of theacceleration-responsive elementshall be provided, if the destgn is such as torequire it in order to protect the mechanism of the accelerometer from possibledamage during shipment. If provid
15、ed, thts device shall be controlled by means of aknurled knob located in the back of the case.3.9.3 Adjustment. The mechanism shall be provided with means to adjust or correctthe indications. This means of adjustment shall be reasonably simple to manipulateand of such a nature that adjustment can be
16、 accomplished with tools ordinarilypossessed by an instrument repairman.3.10 Case. The case shall be in accordance with figure 1 and the requirementsspecified herein. The design of the case shall be such that the mechanism may beremoved from the case and replaced without the use of special tools and
17、 fixturesunless accuracy of dimensions, radii offillets, and marking Of parts and assemblies: thoroughness of soldering, welding,brazing, painting, and riveting;alignment of parts and tightness of assemblyscrews, and bolts; etc.3.17;2 Screw assemblies. Assembly screws and bolts shall be tight. The w
18、ord“tight”means that the screw or bolt cannot be appreciably tightened further withoutdamage or injury to the screw or bolt or threads.3.17.3 Riveting. Riveting operations shall be carefully performed to insure thatthe rivets are tight and satisfactorily headed.3.17.4 Gears. Gear assemblies shall be
19、 properly aligned and meshed, and shall beoperable without interference, tight spots, loose spots, or other irregularities.Where required for accurate ad,lustments, gear assemblies shall be free frombacklash.3.17.5 Cleaning. The accelerometer shall be thoroughly cleaned of loose,spattered, or excess
20、 solder, metal chips, and other foreign material, after finalassembly. Burrs and sharp edges, as well as resin flash that may crumble, shall beremoved.3.17.6 Dimensions. Dimensions and tolerances not specified shall he as close as isconsistent with the best shop practices. Where dimensions and toler
21、ances may affecttheinterchangeability, operation, or performance of the accelerometer they shall beheld or limited accordingly.3.18 Envelope. An envelope, containing the mounting screws, shall be furnishedwith each indicator. .The following information shall be printed on the face of theenvelope:IMP
22、ORTANTTHIS ENVELOPE CONTAINSMOUNTING SCREWS4. QUALITY ASSURANCE PROVISIONS4.1 Responsibility for inspection. Unless otherwise specified in the contract orpurchase order, the contractor is responsible for the performance of all inspectionrequirements (examinations and tests) as specified herein. Exce
23、pt as otherwise10Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-25719B (USAF)spectfied in the contract or purchase order, the contractor may use his own or anyother facilities suitable for the performance of Ehe inspection requirementsspecifie
24、d herein, unless disapproved by the Government. The Government reserves theright to perform any of the inspections set forth In this specfficatton where suchinspections are deemed necessary to ensure supplies and services conform toprescribed requirements.4.1.1 Responsibility for compliance. All Ite
25、ms shall meet all requirements ofsections 3 and 5. The inspection set forth in this specification shall become a partof the contractors overall inspection system or quality program. The absence ofany inspection requirements in the specification shall not relfeve the contractor ofthe responsibility o
26、f ensuring that all products or supplies submitted to theGovernment for acceptance comply with all requirements of the contract. Samplinginspection, as part of manufacturing operations, ts an acceptable practice toascertain conformance to requirements, however, this does not authorize submissionof k
27、nown defective material, either indicated or actual, nor does it commit theGovernment to accept defective material.4.2 Classification of inspections. The inspection requi.remerttsspecffled hereinare classified as follows:a. First article inspection (see 4.6)b. Quality conformance inspection (see 4.6
28、.1)4.3 Acceptance tests. Acceptance tests shall consist of:a. Individual tests (see 4.3.1).b. Sampling plans A and B (see 4.3.2.1 45. 90, 135, 180, 225. 270. and 315 from the initialposition. At each of these positions, the indic8tor shall be rotated on itshorizontal axis until it is in its normal o
29、perating position. The horizontalmagnetic field fntensity shall he 0.17 to 0.19 oersted. The deflection of thecompass at any of the specified positions shall not exceed 1.O.4.5.8 Vibration error. The accelerometer shall be mounted on a suitable vibrationstand with the dial in a vertical plane and wi
30、th the graduation +1 at 270. Theauxiliary pointers shall be displaced approximately I g from the main pointer andthe readings noted. The reset mechanism shal not be operated until the completionof the tests. For a total of 3 hours the accelerometer shall be vibrated at thespecified frequencies at an
31、 amplitude between 0.018 and 0.020 inch, and the pointeroscillation shall be noted. The frequency shall be varted from 500 to 3000 cvclesper minute in a period of not more than 60 minutes. The natural frequency of the15Provided by IHSNot for ResaleNo reproduction or networking permitted without lice
32、nse from IHS-,-,-MIL-A-25719B (USAF)seismic system shall be noted during the frequency variation between 500 and 30()(1cpm. For the remainder of the 3 hours test period, the accelerometer shall bevibrated at a frequency of 1,800 cpm. At the end of the testperiod, the indicationof the auxiliary point
33、er shall be read before operating the reset mechanism. Atfrequencies below 1,200 cpm the oscillation of the main pointer shall not exceed ().2g and at frequencies over 1,200 cpm, the oscillation shall not exceed 0.3 g. Aftervibration, the indications of the auxiliary pointers shall not be changed by
34、 morethanO.1 g. The accelerometer shall not be damaged as a result of this test.4.5.9 Vibration endurance. The accelerometer shall be mounted on theapparatus inits normal operating position. The accelerometer shall be vibrated with circularmotion of 0.018 to 0.020 inch diameter in a plane inclined 4
35、5 degrees to thehorizontal plane and the frequency of vibration shall be varied uniformly from 5 to50 Hz and reset once each hour for a 50-hour period. Upon completion of the testperiod, the accelerometer shall be subjected to the test specified in 4.5.3. Thedynamic scale error shall not exceed 0.2g
36、.4.5.10 Shock. The accelerometer to be,installed in the normal operating PositIonis a free-fall apparatus as described in 4.5.10.1. If provided with a lockingdevice, the accelerometer mechanism shall be locked. The accelerometer shall beallowed to fall from a height of 8 inches; then examined for da
37、mage and subjected tothe testspecified in 4.5.3. There shall be no damage to the accelerometer and thesteady state scale error shall not exceed 0.2 g.4.5.10.1 Apparatus. A rigidly constructed device provided with a panel mountingfor installing the accelerometer in the specified position, and vertica
38、l guides toallow free-fall from the specified height shall be used. A bumper on the free-fallelement shall arrest its fall by striking the center of a rounded projection on ametal cross section with an unsupported length of 5 inches between points ofattachment to the free-fall element. The bumper sh
39、all contact the metal block atthe midpoint of a broad side. The center of gravfty of the instrument under testand the contact point of the bumper shall be aligned vertically within 0.125 inch.The weight of the free-fall element shall be approximately 12 pounds. The metalblock shall weigh not less th
40、an 50 pounds.4.5.11 Mounting lugs. The accelerometer case with mechanism and cover glassremoved shall be mounted face downward on the movable head of a suitable testingmachine with the diameter of the case in a horizontal plane so that the mountinglugs receive no added support. A suitable pin shall
41、be inserted through the hole inthe mounting lug and attached to a pull strap in the stationary head of the machine.a load of 175 pounds shall be applied along the axis of the mounting hole and towardthe front of the case for a period of 1 minute. There shall be no fracture.4.5.12 Low temperature - h
42、igh altitude. The accelerometer shall be placed withinthe test chamber and the chamber cooled to and maintained at a temperature of -62C(-80”F) and at an altitude of 70,000 feet (1.31 inches Hg) for a period of 72 hours,at which time the accelerometer shall be inspected in accordance with therequire
43、ments of 4.4.8. The temperature of the chamber shall then be raised to -54C(-65”F) and maintained for an additional 24-hour period. At the conclusion of thisexposure period and while at this temperature, the accelerometer shall be inspectedand operated in accordance with 4.4.8. The accelerometer tem
44、perature shall then bereturned to that of standard conditions and the accelerometer operated and inspectedvisually as specified in 4.4.8. There shall be no damage to the accelerometer as aresult of this test.16Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
45、IHS-,-,-MIL-A-25719B (USAF)4.5.13 Humidity. The accelerometer shall be placed in the test chamber and set upto simulate installed conditions. The test chamber shall be vented to theatmosphere to prevent the build-up of pressure. Prfor to the starting of the testperiod, the chamber temperature shall
46、be between 20 and 38C (68 and 100”F) withuncontrolled humidity. During the first 2-hour period, the temperature shall begradually raised to 71C (160”F). This temperature shall be maintained during thenext 6-hour period. The velocity of the air throughout the test area shall notexceed 150 feet per mi
47、nute. During the following 16-hour period, the temperature inthe chamber shall be gradually reduced to 20 to 38C (68 to 100”F) whichconstitutes one cycle. The relative humidity throughout the cycle shall be 95percent. Steam or distilled water having a pH value between 6.5 and 7.5 at 25C(77”F) shall
48、be used to obtain the desired humidity. The cycle shall be repeated asufficient number of times to extend the total time of the test to 240 hours (10cycles). At the conclusion of the 240 hour period, the accelerometer shall bereturned to standard conditions. The accelerometer shall then be operated
49、andinspected within 1 hour as directed in 4.4.8.4.5.14 Fungus. The accelerometer shall be subjected to the fungus resistance testin accordance with MIL-STD-81OD, Method 508.3.4.5.14.1 Organism.Group I - Chaetomium globosumMyrothecium verrucariaGroup 11 - Memenoniella echinataAspergillus nigerGroup 111 - Aspergillus flavusAsper.llus terreusGroup IV - Penicillium citrinumPenicillium ochrochloron 9112.6205909595976275108361069098494.5.14.2 Stock culture
