MIL-STD-202H.pdf - 第302页
MI L - S TD - 202 -3 1 2 CO NT E N T S PARAGRAPH PAG E FOREW ORD … ………………………………………………………. ii 1. SCOPE 1 1.1 Purpose …… ………………… …………………. …… .. …………. 1 1.2 Precaution s …………………… ……………. ……………………. 1 2. APPLICABLE D O C U M E…
MIL-STD-202-312
FOREWORD
1. This standard is approved for use by all Departments and Agencies of the Department of Defense.
2. This entire standard has been revised. This revision has resulted in many changes to the format, but the most
significant one is the splitting the document into test methods. See MIL-STD-202 for the change summary.
3. Comments, suggestions, or questions on this document should be emailed to std202@dla.mil or addressed to:
Commander, Defense Logistics Agency, DLA Land and Maritime, ATTN: VAT, P.O. Box 3990, Columbus, OH
43218–3990. Since contact information can change, you may want to verify the currency of this address
information using the ASSIST Online database at https://assist.dla.mil.
ii
北测（上海）电子科技有限公司
联系方式：xuyj@beice-sh.com 13917165676
MIL-STD-202-312
CONTENTS
PARAGRAPH PAGE
FOREWORD…………………………………………………………. ii
1. SCOPE 1
1.1 Purpose………………………………………….……..…………. 1
1.2 Precautions………………………………….……………………. 1
2. APPLICABLE DOCUMENTS 1
3. DEFINTIONS 1
4. GENERAL REQUIREMENTS 1
4.1 Apparatus…………..……………………………...….….…..….. 1
4.1.1 Test circuit…..……………………………..….….…………..….. 1
4.1.2 Monitoring apparatus……………………..….….…………..….. 2
4.2. Procedure…………………………………..….….…………..….. 2
5. DETAILED REQUIREMENTS 2
5.1 Summary…………………………………………..…..…………. 2
6. NOTES 3
6.1 Supersession data………………………………………………. 3
iii
北测（上海）电子科技有限公司
联系方式：xuyj@beice-sh.com 13917165676
MIL-STD-202-312
METHOD 312
INTERMEDIATE CURRENT SWITCHING
1. SCOPE
1.1 Purpose. This test is conducted for the purpose of determining the electrical contact reliability of such items as
electromechanical relays, switches, etc., under intermediate current (formerly known as "minimum current") switching
conditions under which the contacts operate. An intermediate current switching circuit is one in which there is
insufficient voltage and stored energy to cause contact arcing during opening or closing of mating contacts, but which
have sufficient energy to cause melting of the contact material. Normal arcing of contacts at rated load levels often
act to burn off any oxide or other film on the contacts or provide localized melting at the point of contact, so that
contact resistance does not rise drastically. Without this arcing of the contacts, oxides and other contaminant films
can build up on contacts in component parts which have not been sealed adequately or which have contaminating
materials and vapors trapped within the enclosure due to improper manufacturing techniques. Such contacts will
develop unacceptably high contact resistance under intermediate current loads, unless the contact force and wipe are
sufficiently heavy to overcome any effect of contamination. Intermediate current switching is the range in which a
large percentage of loads occur. Therefore, it is extremely important that an intermediate current switching test be
imposed on all electromechanical relays and switches, which are to be used in this range. Relays and switches,
which pass both low level and full rated load tests, frequently fail when used in the intermediate current switching
range.
1.2 Precautions. Full rated load and low level life tests are not a substitute for the intermediate current switching
test. Successful testing at low level and full rated loads in no way reflects the capability of the relay or switch at
intermediate current loads. Statements or titles for component parts, such as "low level to full rated load" shall not be
used in specifications, unless intermediate current switching capability has been demonstrated by the requirement for
testing by this method.
CAUTION: A low-level run-in test is not equivalent to intermediate current testing and conversely intermediate
current capability does not indicate low level capability.
2. APPLICABLE DOCUMENTS
This section not applicable to this standard.
3. DEFINTIONS
This section not applicable to this standard.
4. GENERAL REQUIREMENTS
4.1. Apparatus.
4.1.1 Test circuit. Monitoring of the specified contact resistance of each pair of mating contacts shall be
accomplished on each cycle. Each contact shall be monitored on each closure. The apparatus, which cyclically
operates the contacts, shall be capable of automatically cycling the contacts at the rate specified. Resistive load
voltage shall be applied to the contacts and shall be 3.0 V dc to 10.0 V dc at 100 ±10.0 milliamperes (mA) such as by
means of a well regulated power supply which will provide the low voltage, controllable, and well defined voltage
source. Voltage, when required to energize coils in order to actuate the contacts, shall be as specified. Both
normally open and normally closed contacts of double-throw switching parts shall be tested. Multipole contacts shall
be connected with all normally open pairs of contacts loaded and all normally closed pairs of contacts loaded.
1
北测（上海）电子科技有限公司
联系方式：xuyj@beice-sh.com 13917165676