Triaxial cable

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Structure of a triaxial cable

Triax plug with cable

A triaxial cable is a special form of coaxial cable , which consists of three concentric conductors . These are separated from one another by a dielectric and a shield . Because of the higher manufacturing costs, the cables are more expensive than coaxial cables.

Areas of application are video technology and electrical measurement technology .

In video technology, triaxial cables are particularly widespread in camera systems. As with a coaxial cable, the user data (image, sound, control signals) are transmitted at high frequencies, e.g. B. transmitted by means of frequency division multiplexing on the inner conductor. The additional outer shield conductor is used to power the camera system.

In electrical measurement technology, currents in the femto-ampere range can be measured with a suitable structure using triaxial cables . The inner shield conductor is kept at the same potential as the inner conductor by means of an operational amplifier . This prevents leakage currents to the inner conductor and thus enables high-precision current measurement.

The term "triaxial" for this type of cable is misleading and, on closer inspection, can be traced back to a wrong derivation from the more common word "coaxial". The term “coaxial” literally means “lying on a common axis”, which is correct because the inner conductor and shield are on the same axis. “Triaxial” literally means “with three axes”, which is not the case with triaxial cables. Since all three conductors have a common axis in the triaxial cable, it is actually a coaxial cable, but with three conductors, while a simple, three-pole electrical cable could literally be called a "triaxial cable". In practice, however, this would only lead to misunderstandings due to the widespread use of the wrong terminology.

Individual evidence

1. ↑ Ulrich Schmidt: Professional video technology - Springer . doi : 10.1007 / 978-3-642-38992-4 ( springer.com [accessed April 21, 2017]).
2. ↑ Reinhard Lerch: Electrical measurement technology - Springer . doi : 10.1007 / 978-3-662-46941-5 ( springer.com [accessed April 21, 2017]).