Contact resistance measures the flow of electricity or heat between two surfaces, with larger surface areas having lower resistance. Gold and soft metals are often used in contact pads. High resistance can be caused by loose connections, erosion, contamination, or corrosion. Ohmmeters can test resistivity, taking into account surface area and pressure. Manufacturers provide measuring ranges, and contact resistance is important for monitoring power transmission and fluid pressure.
Contact resistance is often measured to determine the condition of electrical connections, circuit boards, or other types of wire. Typically dependent on the shape of the contact surfaces and layers used for insulation, this type of resistance generally describes the flow of electricity, or heat, from one location to another. Parts with a larger surface area usually have low contact resistance, while those with relatively smaller surface areas tend to have higher resistance. Gold and other soft metals usually have a higher connection surface area, so they are often used in contact pads.
When two components are in contact with each other, the flow of electricity, and also heat in the form of thermal contact resistance, is often affected by microscopic phenomena in the material. Some regions of the metal, for example, are in direct contact and are fully conductive, while other areas may have higher resistance and are only partially conducting. Sometimes there are also non-conducting regions.
Electrical contact resistance can be high if the connections between two plates, or a surface and a probe, are not tight enough. If joints are to be bolted together, a lack of voltage can also affect conduction, while erosion of the contacts or their surfaces often causes high contact resistance. Contamination from dirt or other compounds can also be a factor. The contacts on jump leads often corrode, preventing the flow of electricity from one car battery to another. Corrosion of fuse contacts can also affect device performance.
If there is a high level of current flowing through a device and the contact resistance is high enough, heat can build up and pose further hazards. Test equipment such as an ohmmeter can be used to determine the level of contact resistivity in a connection. When doing this type of testing, it is often necessary to take into account the metal contact surface area, as well as whether the connection is welded, bolted, bolted or welded. Also, the pressure at which the contact is held together is usually considered.
Normal contact resistance is usually identified by the manufacturers of the equipment under test. The correct measuring ranges are often described on product manuals or sometimes directly labeled on the devices. A contact resistance measurement is generally important for monitoring the condition of power transmission lines. It is also sometimes performed to characterize the fluid pressure, which can behave much like an electrical voltage, between different flow channels.
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