Cables and connectors are the easiest and most difficult to test objects, and usually have to be done at the same time; an interconnect component that handles RF, especially tens of GHz signals, can be tricky to test... why? Because everything affects performance, including settings, test instrumentation and settings, material, dimensional accuracy, bending, and how it works, it can affect test performance.
There is another common connection scheme that should be easier to detect, which is a widely used crimping link; in principle, this connection is very straightforward because the connector is a manual or electric-assisted crimping pliers (crimper). Squeeze onto the line, the lines and connectors are deformed in a plastic (plasTIc) mode and tightly combined into a pair, so they should be physically and mechanically strong. If fabricated correctly, the crimped interconnect has low impedance, is reliable, and has the added advantage of being relatively inexpensive.
There are many types of crimp connectors on the market, including fork and ring terminals (as shown below); but according to my colleague, EE TImes/EDN senior technical editor experience, poor crimp connectors can cause heat or even fire.
There are many crimp connectors in the shape and size to meet different application needs.
Paradoxically, although the crimp joint is completely visible to the naked eye, it is difficult to detect; many factors can cause errors, such as unevenly applied crimping force, unaligned lines, and too much pressure (which may cause solid or standard lines to appear small). Cracks), the pressure is too small (usually causing intermittent connections due to vibration)...etc.
It is not appropriate to detect the quality of the crimp link by means of a pull-to-failure test, because the link itself needs to be destroyed; the disassembly can only be used to randomly test the sample or to verify the design. set. So how do you test these links in a fast and non-destructive way? They are all important link interfaces to the system and reliability is very important.
To solve this problem, the Langley Research Center of NASA has proposed a real-time ultrasonic device (as shown below) to determine whether the link has passed the test with advanced signal analysis; the system (now An authorization can be provided to deliver a sound wave into the crimp connection.
NASA has developed a tool to test the quality of crimp connectors
According to NASA, as the applied pressure increases and the crimp junction ends deform around the line, the ultrasonic waveform across the link changes; the system analyzes signal changes, including amplitude and frequency, to As a pointer to determine the electrical and mechanical link quality of the line and the connection terminal (as shown below).
Easily judge the quality of the crimped link with the ultrasonic signal waveform
NASA pointed out that different crimp link quality problems, such as insufficient crimping force, missing strands, incomplete line insertion, loss of insulation, and incorrect line specifications, can be tested in this way.
This sophisticated and clearly effective crimp joint test method is not only easy to use, but can also be performed during the joint manufacturing process, not until the production is completed; if there is any problem with the crimp joint, the operator can Stop the action and find the error immediately before the destructive method is solved. If the link passes the test, the line can be immediately connected to the endpoint, eliminating the need to subsequently process the cable (usually in a large harness).
The method of ultrasonic analysis is not based on a single number or a single set of numbers, but on the cumulative data to define whether the test passes; for example, one of the methods is to measure one or more applied to the crimped connection during the crimping process. The pressure at a particular point is actually a minor part of the evaluation of the crimping process, rather than seeing the actual integrity of the crimped joint through the ultrasonic waveform.
The author suspects that as we gather more information, we have the ability to make smaller, lower-cost measurement devices (such as ultrasonic transceivers) and to develop intelligent algorithms that will lead to more such test scenarios. In many cases, measuring only a single number may not be enough, and we now have more powerful tools to use.
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