June 2010: MIL Connector Quiz Results

Thank you to everyone who participated in our 2nd Quiz challenge. After collecting a month's worth of anonymous data you can now compare your Quiz results against a large cross-sampling of others who also took the quiz. See which questions were the tough ones!

Look for "What is Your Cable Testing IQ - Challenge #3 - in a future issue of this newsletter.

How did you do?

Questions answered correctly:

1-3 Electronics can be a shocking experience for you!
4-5 You're in the "half that makes the top half possible!"
6-7 Not bad, this cable testing stuff is easy, isn't it?
8-9 Don't agree with one or two answers do you?
10 "...A flux capacitor is overdue Doc!"

"Cable Testing IQ" - Challenge #2 Quiz Answers!

Correct answers in red.

Question #1:

There is a 'J' or 'JAN' preceding the 'MS' or 'D38999' in my connector part number. What does this mean?

(08%) A. Prefix of the full PN that most people ignore.
(69%) B. Not part of the part number, it indicates the connector was built to the standard by approved JAN Source.
(13%) C. Signifies Jam Nut Style connector.
(11%) D. Kind of metal the shell is made from

The United States Government has adopted, and is exercising legitimate control over the certification marks, "JAN" and "J", respectively, to indicate that items so marked or identified are manufactured to, and meet all the requirements of specifications. For complete details follow this link: MIL_STD-5015.pdf (nasa.gov)

Question #2:

What is the difference between a MIL-C and MIL-DTL specification?

(23%) A. C Designates acceptable for Commercial use.
(04%) B. MIL-DTL means date listed.
(15%) C. Indicates differences in plating of connector shell.
(57%) D. DTL is Short for Detail.

This was one of the tougher questions, with only 57% of respondents answering correctly. There has been a shift in the industry away from MIL-C to MIL-DTL or MIL-PRF specifications. MIL-DTL means Detail Specification. A specification that contains design requirements, such as materials to be used, how a requirement is to be achieved, or how an item is to be fabricated or constructed. A specification that contains both performance and detail requirements is still considered a detail specification.

MIL-PRF is a Performance Specification. A performance specification states requirements in terms of the required results with criteria for verifying compliance, but without stating the methods for achieving the required results. A performance specification defines the functional requirements for the item, the environment in which it must operate, and interface and interchangeability characteristics.

Question #3:

What type of connector shell is this?

Fig 1. Plug Style Connector

(44%) A. Plug
(40%) B. Receptacle
(08%) C. Cannon Plug
(07%) D. Not enough information to answer

Tricky question, only 44% of our test takers got this one right. Don't make the mistake of associating Plugs with pins and Receptacles with sockets. Plugs always have the ""outside"" ring that couples cylindrical connectors together, regardless of what type of contacts they have.

Question #4:

What type of connector is this?

Fig 2. Receptacle with Pin Contacts

(14%) A. Plug with Male Contacts?
(81%) B. Receptacle with Pin Contacts?
(02%) C. Receptacles with Socket Contacts?
(03%) D. Not enough information to answer.

81% of respondents got this one correct, likely assisted by learning the difference between plugs and receptacles in the previous question.

Question #5:

Which of the following is 'NOT' a valid MIL style shell type?
cableconn-240 (7K)

(34%) A. Cable Connecting Receptacle?
(08%) B. Threaded Receptacle?
(21%) C. Bayonet Plug?
(37%) D. Jam Nut Plug?

Another tricky question. Many people incorrectly answered Cable Connecting Receptacle. Some connector series do have Cable Connecting Receptacles. Jam Nuts are a way of fastening a receptacle to a panel when the receptacle does not have holes for screws. You won't ever see a Jam Nut Plug.

Question #6:

What does the blue band on a cylindrical connector mean?

Example of Blue Band on Receptical Connector with Pins

Fig 4. Blue Band on Receptical Connector

(07%) A. Only Blue Sealing plugs fit into it.
(12%) B. Approved for MIL-SPEC use
(20%) C. Rear Release Connector
(62%) D. Blue band not visible means plug is fully mated

This question tripped up too many people and we decided it was misleading so we re-worded it. In some connector series there is a red band to indicate the plug is not fully engaged. If there is a red and a blue band, the red band serves this purpose. We did find receptacles with a blue band only. In this case the band is positioned so that it might indeed help identify connectors not fully mated.

To fix this question we re-worded it so it refers to the blue band on plugs only. In this case such a band will not indicate the connectors are fully mated because the blue band is always visible on plugs, even after full mating. If you missed this question on your first try, give yourself an extra point!

Fig 5. Blue Band on Plug Style Connector

Question #7:

When ordering connectors, the "contact type" position of the part number can have an 'A' or 'B' or 'P' or 'S', what does this mean?

(68%) A. P/S means you are ordering with, A/B without contacts"
(10%) B. A/B means commercial, P/S military.
(06%) C. Plating material used on contacts.
(17%) D. None of the above!

Nearly 70% of you got this one correct. A/B on the part number description means you are ordering the connector sans contacts. Since the A/B does not show up on the connector body, if you don't see the part number or packaging you may not be even aware of this difference. If you've ever wondered why sometimes there are no pins in the bag with the connector, now you know.

Question #8:

In the following picture of an insertion/removal tool:

Fig 6. Insertion / Extraction Tool

(66%) A. Green is for Insert, White for Removal
(23%) B. White is for insertion, Green for Removal.
(08%) C. Either side can be used for insertion/removal.
(03%) D. It does not matter, they don't come out anyway!

66% got this one right. If you closely inspect the ends of a tool you will find that the end that inserts has less plastic than the end that removes. This makes it less likely that insertion results in removal as you remove the tool.

(If you're one of the 3% who answered "D. It doesn't matter, they don't come out anyway" give yourself half a point!)

Question #9:

Once a contact is locked in I can't get it out, how come?

(14%) A. Using Wrong Tool.
(02%) B. Insulation is too thick.
(04%) C. Diameter of contact is damaged.
(80%) D. Any of the above.

80% got this correct.
It is clear from this question that most people taking this quiz have had some real world experience.

Question #10:

When electrically testing a cable/harness built with MIL-SPEC connectors should a test point be connected to the metal shell of the mating test connector?

(11%) A. Only if shell to shell connections.
(02%) B. Never, you could damage the shell.
(84%) C. Always, you need to check for shorts to the shell.
(02%) D. No, the test equipment supplier is just trying to sell more test points.

Test specifications such as 83575 and MIL-STD-202 method 301/302 have this requirement.
Consider what happens if a wire connected to a contact is shorted to the shell of a plug. If the assembly is tested without detection of this short, as soon as the cable is connected to a receptacle mounted into a metal panel, you have a short from that wire to the panel.