March, 2024
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Using Spring-Probes and Contacts for Electrical Test of Wire Harness Assemblies
well as HKR/HKF clamping probe designs.
Testing can be done with
traditional “test tables” or with so-called “test plugs” (which are also sometimes called “test fix- tures”). Whereas test tables for harness test are very common in production regions such as in
WHMA-A-620 when designing a test plug (as the standard main- ly applies to finished products, for permanent installation), it is still highly recommended to use the principles of those standards as this ensures high reliability and uniformity. With new requirements
from the EV industry and requirements to check for seal-
ing/leakage of connectors, as well as high-speed test testing, test probe designs have become quite complex. Many of those products have little in common anymore with the traditional three-piece architecture. Some probes are composed of thirty individual components and more, in very small form factors. Be prepared for even higher data-rate
requirements in the future and higher current carrying capacity requirements for the connectors and consequently for the test probes.
Contact: INGUN USA, Inc.,
252 Latitude Lane, Suite 105- 106, Lake Wylie, SC 29710 % 803-831-1200 E-mail:
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Clamping probe.
Mexico, there has been a trend toward “test plugs” in the United States and Canada.
Probe Designs
l Standard — in its simplest form the probe consists of a bar- rel, a plunger, and a spring. The contacting surface is plated to ensure good contact. For wire harness application, typically a thread-mounting feature is used for installation as opposed to a push-fit type which is used in a clam-shell/bed-of-nails fixture design.
l Coaxial — coaxial probes have two conductors, a center, and an outer conductor. Both conduc- tors are spring-loaded. Coaxial designs are in use for RF, speed, and Kelvin/4 wire test.
l Bifurcated-tip — with bifur- cated designs, the tip expands upon compression. For a connec- tor test, a “tulip” tip is used which expands once the probe is activated inside the connector.
l Pushback — a pushback probe has a high-spring force and is used to check for pin retention in a connector.
l Switch — a switch probe has a built-in mechanical switch. This can be used to detect the pres- ence of certain features in a con- nector or sometimes just to sig- nal the start of a measurement when the probe is activated.
l Pneumatic — a pneumatic probe is activated with air rather than mechanical com- pression. Individual and sequen- tial contact onto connectors is possible, rather than activating all probes at once as is the case with spring-probes.
While it is not required to use standards such as IPC
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