MIL-STD-202H.pdf - 第222页

MI L - S TD - 202 - 217 M E T H O D 217 PAR T I C L E I M PAC T N O I SE D ET EC T I O N (PI N D ) 1. SCOPE 1. 1 P urpose . T he pur po s e o f t hi s t es t i s t o det e c t t he pr es e n c e of f r ee m ov i n g par …

MIL-STD-202-217

CONTENTS

PARAGRAPH PAGE

FOREWORD…………………………………………………………. ii

1. SCOPE 1

1.1 Purpose………………………………………….……..…………. 1

2. APPLICABLE DOCUMENTS 1

2.1 Non-Government publications……………………………….… 1

3. DEFINTIONS 1

4. GENERAL REQUIREMENTS 1

4.1 Apparatus……………….…….…………………….….........……. 1

4.2. Procedure…………….………………………..….….………….. 2

4.2.1 Calibration..……………....…………………..……..……………. 2

4.2.2 Test setup…….……………………………………….………….. 2

4.2.3 Test procedure…….…………………………..……..……….…. 2

4.2.3.1 Degausing………………………….…………..……..……….…. 2

4.2.3.2 Lead protection……………….…………..……..…………….…. 2

4.2.3.3 Testing………….…………..……..…………………………..…. 3

4.2.3.4 Marking…….……………….……..…………………………..…. 3

4.2.3.5 Failed units………………….……..…………………………..…. 3

5. DETAILED REQUIREMENTS 3

5.1 Summary…………………………………………..…..…………. 3

6. NOTES 7

6.1 Supersession data………………………………………………. 7

FIGURES PAGE

1. Typical test circuit…………………………………………………………... 4

2. Representative oscilloscope traces..……………………………………... 5

3. Shock test fixture…………………………………………….……………... 6

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MIL-STD-202-217

METHOD 217

PARTICLE IMPACT NOISE DETECTION (PIND)

1. SCOPE

1.1 Purpose. The purpose of this test is to detect the presence of free moving particulate contaminants within

sealed cavity devices. This test method is specifically directed toward relays and other devices where internal

mechanism noise makes rejection exclusively by threshold level impractical. This test method also may be used prior

to final sealing in the manufacturing sequence as a means of eliminating loose particles from the interior of the

device.

2. APPLICABLE DOCUMENTS

2.1 Non-Government publications. The following documents form a part of this document to the extent specified

herein. Unless otherwise specified, the issues of these documents are those cited in the solicitation or contract.

NATIONAL CONFERENCE OF STANDARDS LABORATORIES (NCSL)

NCSL Z540.3 - Requirements for the Calibration of Measuring and Test Equipment

(Copies of this document are available online at www.ncsli.org)

3. DEFINTIONS

This section not applicable to this standard.

4. GENERAL REQUIREMENTS

4.1. Apparatus. The basic PIND system is comprised of the following components: (Substitutions of individual

units or complete system may be made providing the test requirements of paragraph 3 are met.)

a. Vibration power source consisting of electrical driver audio oscillator and low frequency audio amplifier.

b. Ultrasonic sound detection system consisting of a crystal transducer with frequency response of 36 kHz - 44

kHz and associated translator preamplifier capable of converting transducer output to 20 Hz - 5 kHz.

c. Small vibration shaker or two shakers coupled together.

d. Oscilloscope, single beam, with 100 kHz minimum bandwidth capable of external synchronization.

e. Audio speaker or headset.

f. Test fixture to adapt transducer to shaker head and isolate it from external noise sources.

g. Holding fixture designed to hold flat surface of unit under test firmly against the sensing surface of the

transducer.

h. Shock test fixture (see figure 3).

i. Calibration unit per 4.2.1c.

j. Random vibration generator.

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MIL-STD-202-217

4.2. Procedure. Test equipment shall be assembled as shown on figure 1. System calibration, as defined in

4.2.1b, shall be performed at the following intervals:

a. Each time equipment is turned on.

b. Each change of operators.

c. At initial and completion of test for each group of devices.

d. Every four hours throughout testing.

Whenever system sensitivity is found to be below specified minimum, all units tested subsequent to previous

acceptable calibration shall be retested. Units rejected for particle noise shall not be reworked or retested for the

purpose of acceptance. Units rejected for excessive mechanism noise may be retested for the purpose of eliminating

the mechanism noise.

4.2.1 Calibration.

a. Each unit of test equipment subject to calibration shall be maintained in accordance with NCSL Z540.3.

b. System calibration shall consist of verifying the proper oscilloscope pattern while calibration unit is being

energized by the shaker head at the frequency and acceleration specified in 4.2.2. Calibration shall also

include elimination of extraneous noise which interferes with proper performance of the test.

c. Test the system with a container (size approximately ½" (12.7 mm) X 1" (25.4 mm) X 1" (25.4 mm) or

smaller) which contains a 60/40 solder ball with a diameter of 0.005’’. Listen to the audible sound and

observe the oscilloscope response to the solder ball.

d. Test the system with a container (size approximately 1/2" (12.7 mm) X 1" (25.4 mm) X 1" (25.4 mm) or

smaller) which contains no particle, and compare the audible sound and the oscilloscope response to the

results of step c to insure that particles are detectable.

4.2.2 Test setup. The area in which the PIND system is used shall be carefully selected to avoid external

interference from electrical and mechanical noise which will decrease the effectiveness of the test.

a. Set audio oscillator to 27 ±1 Hz.

b. Adjust audio amplifier to produce 3-5g (.07" (1.78 mm) - .14" (3.56 mm) displacement) at shaker head.

c. Check mechanical and electrical systems to minimize background noise. Background noise shall not

increase more than 3 dB when shaker is placed in operation (except shaker reversal noise) and total system

noise shall not exceed 20 mV. Adjust oscilloscope trace to less than 4 divisions displacement and center

shaker reversal noise as shown on figure 2a. No other noise spikes shall be detectable.

d. Adjust audio output to comfortable level.

e. With calibration unit mounted on shaker verify proper oscilloscope and system sensitivity to produce random

noise spikes of 40 mV minimum (figure 2c).

4.2.3 Test procedure.

4.2.3.1 Degausing. Devices not incorporating permanent magnets and devices being tested prior to final

magnetization shall be degaused prior to PIND testing.

4.2.3.2 Lead protection. When a device incorporates relatively long and flexible leads, the leads shall be suitably

restrained from striking the shaker/fixture or striking each other during test. Care shall be taken to prevent damage

caused by resonance.

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联系方式：xuyj@beice-sh.com 13917165676