1、MIL-M-28942 (MC) 3 February 1970 SUPERSEDING See Section 6. MI LI TARY SP ECi F IC AT i ON MULTIMETER: PORTABLE, BATTERY POWERED, AN/USM-l23A 1. SCOPE 1.1 This specification covers the requirements for one type multimeter used for the measurement of alternating current (ac) and direct current (dc) v
2、oltages, dc current, and resistance. 2. APP LICAB LE DOCUMENTS 2.1 for bids or request for proposal, form a part of the specification to the extent specified herein. The following documents, of the issue in effect on date of invitation SP EC i Fi CAT I O NS F ED ERAL P P P - B-636 -Box, Fiberboard.
3、Mi LI TARY MI L-M-14 -Mo Id ing Plastics and Mo Ided . Plastic.Parts, Thermosetting. MI L-P-116 -Preservation, Methods of. MI L-S-6872 -Soldering Process, General Specification for. MI L-M-16034 -Meters, El ec trica I -Ind ica ti ng (Switchboard and Portable Types). / STANDARDS MI LI TARY MI L-STD-1
4、05 -Sampling Procedures and Tables for inspection by Attributes. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-M-287LI2 bb m 7977706 033b5b3 5 m MIL-M-28942 (MC) MI L-STD-129 -Marking for Shipment and Storage. (Copies of specifications and stan
5、dards required by suppliers in connection with specific procurement functions should be obtained from the procuring activity or as directed by the contracting officer.) 3. REQUIREMENTS 3.1 First article. As soon as practicable after award of contract or order, and prior to starting production, the m
6、anufacturer shall submit three first articles to the contracting officer or his authorized representative for examination and approval. Each first article shall be complete with calibration procedures. The first articles shall be representative of the construction, workmanship, components, and mater
7、ials to be used during production. Approval of the first articles does not precludethe requirements for performing the quality conformance inspection. 3.2 Material. The material for each part of the. multimeter shall be as specified herein. When a definite material is not specified, a material shall
8、 be used which is adequate for the purpose intended and for meeting the requirements specified herein. Acceptance or approval of any constituent material for a particular part shall not be construed as a quaranty of the acceptance of the finished product. 3.2.1 Case material. Molded thermosetting pl
9、astic material of medium to high impact type conforming to Mi L-M-14 shall be used for the case. The material shall be of the proper type for the intended use. 3.2.2 Components and parts. Electrical and electronic components and parts used in the multimeter shall show no evidence of mechanical or el
10、ectrical breakdown, deterioration, corrosion, or breakage as a result of any requirements herein and shall be adequate for the purpose intended. 3.3 Design and construction. This specification covers a self-contained, portable, multiple-function meter, Multimeter AN/USM-l23A. The multimeter shall be
11、 used for the measurement of dc voltages to 4,000, ac voltages to 800, the ac portion of output voltages to 160, volume levels to 45 decibels (dB), dc amperes to 8, and resistances to 200 megohms. The multimeter shall be housed in a nonmetallic case with a carrying handle attached. The multimeter sh
12、all be supplied with a suitable pair of plug-in test leads, removable alligator clips, a 4,000-volt o/) probe extension for use with the test leads. The meter dial shall be a minimum of 6 inches arc length. The multimeter shall be powered by one or more dry-cell batteries of adequate capacity - Prov
13、ided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-M-28942 (MC) for operation of the resistance measurement section which shall be contained within the case. No external power source shall be required. 3.3.1 Circuitry. All circuitry shall exhibit suffic
14、ient stability to maintain calibration withmable tolerances specified herein, without resetting any internal controls during performance requirements tests. 3.3.2 External controls and connectors. External controls and connectors shall be keptto a reasonable minimum. External controls and connectors
15、 shall be designed and posi tioned to afford maximum convenience, minimum projection from surface of case, and maximum conformance to the physical.configuration of the multimeter. External controls and connectors shall include, but not be limited to, the fol lowing: (a) Range selector switch (b) Fun
16、ction selector switch (c) Ohm zero-adjust control (d) Test lead connectors. Any combination of switches may be provided to obtain the stated requirements. 3.3.2.1 Selector switches. Range and function selector switches shall be suitably indexed and marked so that the correct scale can be easily sele
17、cted. Selector switches shall be designed to eliminate danger of electric shock to the operator., Selector switches shall have a life of 10,000 continuous no-load operations, when tested as specified in 4.5.7. 3.3.2.2 Ohms zero adjust control. An ohms zero adjust control shall be provided on the fro
18、nt panel of the instrument to adjust the meter pointer to zero on each ohms range when the function selector switch and the range selector switch are set to ohms and the ohmmeter leads are shorted. 3.3.2.3 Lead connectors. Lead connectors shall be of the type to receive banana spring-tip plugs. Lead
19、 connectors shal I maintain positive electrical and mechanical contact with the test leads after 25 repeated withdrawals of the test leads when tested as specified in 4.5.8. 3.3.3 durability. The case shall be equipped with a suitable carrying handle for con- venience in transportability. The case s
20、hall be designed to permit convenient Case. The multimeter shall be housed in a molded case of.suitable Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-M-28742 bb m 777770b OL3b565 7 W MI II-M- 28 942 (MC) accessability to the interior of the mul
21、timeter for service and repair, including battery replacement. 3.3.4 Dial. The dial face shall be a minimum 6-1/2 inches wide. Arc length of longest scale shall be 6 inches minimum. The pointer shall be of suitable size and material for the intended purpose. The dial shall b covered with a pro- tect
22、ive glass window or other suitable material of sufficient strength to afford desired protection to the dial. Window material and means of securing shall be in accordance with MI L-M-16034. - 3.3.5 Test leads. One pair of test leads shall be supplied with the multi- meter. The test leads shall be col
23、or coded, one red and one black. One end of each test lead shall be fitted with suitable test prods. Alligator clips shall be pro- vided which can be securely and quickly fitted over the test prods. The high voltage test prod shall be designed for easy attachment and for maximum protection to the op
24、erator against electrical shock. The opposite end of each test lead shall be fitted with a banana spring-tip plug. Fit of test leads into leadzonnectors of the multimeter shall meet the test specified in 4.3.4.5. 3.3.6 Soldering. Soldering of electrical connections shall be in accordance with MI L-S
25、-6872. 3.4 Performance. The multimeter shall meet the fol lowing performance requirements. 3.4.1 Direct current voltmeter section. The dc voltmeter section of the multimeter shall have a range of O to 4,000 volts direct current (Vdc). The full range shall be covered by a minimum of seven range steps
26、; the lowest range shall not exceed 0.8 Vdc. Measurements at all ranges except the highest range, to 4,000 Vdc, shall be accomplished by means of the range selector switch and components within the multimeter; no external attachments are required. Measurements at the highest range, to 4,000 Vdc, sha
27、ll make use of a high voltage probe attachable to one of the test leads. Sensitivity shall be 100,000 ohms per V. Direct current accuracy shall be h3 percent of the full scale when tested as specified in 4.5.2. 3.4.2 Alternating current voltmeter section. The ac voltmeter section of the multimeter s
28、hall be capable of making three types of ac measurements: (a) Alternating current voltage (b) Audio frequency output voltage (c) Volume level. 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-1-28742 66 H 7797706 0136566 O MIL-M-28942W) 3.4.2.1
29、Alternating current voltage. The ac voltmeter section of the multime- ter shall have a range of O to 800 volts alternating current (Vac), The full range shall be covered by a minimum of seven! range steps, the lowest range shall not exceed 3 Vac. Measurements of all ranges shall be accomplished by m
30、eans of the range selector switch and components within the multimeter; no external attachments are required. Alternating current accuracy shall be S percent of.the full scale when tested as specified in 4.5.3. Sensitivity shall be 5,000 ohms per V. 3.4.2.2 Audio frequency output voltage. The multim
31、eter shall have a range of O to 160 Vac for measuring the ac portion of an output voltage. The full range shall be covered by a minimum of four range steps, Measurements at all ranges shall be accomplished by means of the range selector switch and components within the multimeter; no external attach
32、ments are required. Accuracy shall be S percent of the full scale. Sensiltivity shall be 5,000 ohms per V in series with a 0.1 micro- farad capacitor . 3.4.2.3 Volume level. The multimeter shall have a minimum range of -10 to +45 dB for volume level measurements. The full range shall be covered by a
33、 minimum of four overlapping range steps. Measurements at all ranges shall be accomplished by means of the range selector switch and Components within the multimeter; no external atiuchments are required. Accuracy shall be S percent of the full scale. Sensitivity shall be 5,000 ohms per V. Calibrati
34、on shall correspond to power developed across 600 ohms, and zero power level at 0.001 watt. 3.4.3 Direct current ammeter section. The dc ammeter section of the multimeter shall have a range of O to 8 amperes. The full range shall be covered by a minimum of seven range steps; the lowest range shall n
35、ot exceed 20 micro-. amperes. Measurements at all ranges shall be accomp1ished:by means of the range selector switch and components within the multimeter; no external attachments are required. Accuracy shall be 52 percent of the full scale when tested as specified in 4.5.4. 3.4.4 Ohmmeter section, T
36、he ohmmeter section of the multimeter shall have a resistant-megohms. The full range shall be covered by a minimum of six range steps. Measurements at all ranges shall be accomplished by means of the range selector switch and components within the multimeter; no external attachments are required. Ac
37、curacy shall be $2 degrees of linear arc when tested as specified in 4.5.5. 3.4.5 Overload protection. The multimeter shall be equipped with overload features for protection against momentary and sustained overloads. Overload pro- tection features shall include, but not be limited to, the following:
38、 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-1-28942 66 M 797790b 0336567 2 MIL-M-28942 (MC) (a) Replaceable fuse type protection at the input (b) Semiconductor diode type protection at the meter movement Overload protection systems shal I pr
39、otect the multimeter and meter movement from overloads of rated capacity when tested as specified in 4.5.6. 3.4.6 Meter movement. The meter movement shall be the tautjband annular type to provide self-shielding and resistance to damage by shock. Satisfactory operation of the meter movement shall be
40、determined by other tests specified herein. 3.5 Dimensions. The dimensions of the multimeter shall be such that the multimeter is convenient to use as both a portable and a bench test instrument. The girth (face perimeter) plus the depth, and the height shaI:I be not greater than 25 inches and 8 inc
41、hes, respectively. 3.6 Weight. The uncrated weight of the multimeter, ready for use with the batteries installed, shall be not greater than 5.5 pounds. 3.7 Workmanship. Multimeters shall be processed in such a manner as to be uniform in quality. The interiors of the multimeters shall be free from me
42、tal filings, grease, oil, foreign material, dust, or other loose particles which will affect life, serviceability, or appearance. 4. QUALITY ASSURANCE PROVISIONS 4.1 Responsibility for inspection. Unless otherwise specified in the contract or purchase order, the supplier is responsible for the perfo
43、rmance of al inspection requirements as specified herein. Except as otherwise specified in ts contract or order, the supplier may use his own or any other facilities suitable for the performance of the inspection requirements specified herein, unless disapproved by the Government. The Government res
44、erves the right to perform any of the inspections set forth in the specification when such inspections are deemed necessary to.assure that supplies - and services conform to prescribed requirements., 4.2 Classification of inspection. The inspection requirements specified herein are classified as fol
45、lows: (a) First article inspection (see 4.3) (b) Quality conformance inspection (see 4.4) (c) Preparation for delivery inspection (see 4.6). Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Test Tests - Group A: Exam i nation Section 3 4.5.1 Direct cu
46、rrent voltage accuracy 3.4.1 4.5.2 Alternating current vol tage 3.4.2.1 4.5.3 Direct current ammeter accuracy 3.4.3 4.5.4 Ohmmeter accuracy 3.4.4 4.5.5 accuracy Overload 3.4.5 4.5.6 Group B: Selector Switches Test lead connectors Test leads 3.3.2.1 4.5.7 3.3.2.3 4.5.8 3.3.5 4.5.8 4.3.1 Adjustmenfs d
47、uringlfirst article testing. After the first article tests have started, only adjustments by externally available controls, without the use of tools, will be permitted. Any other adjustment, repair, or replacement shall be considered a failure. 4.3.2 Failure. Random component failures shall not nece
48、ssarily constitute grounds for disapproval. Repeat failures shall be considered grounds for disapproval. Repeat failures are defined as follows: (a) More than one failure of a specific component (reference symbol) in a single test article. (b) Failure of the same component (reference symbol), in mor
49、e than one test article, (c) More than one failure of different but related components in a circuit. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-M-28942 (MC) 4.4 Quality Conformance inspection. The quality conformance inspection shall consist of the following: (a) Individual . After the multimeters have been properly calibrated, each multimeter shall undergo the tests specifi
