Single-End Shield Grounding
The practice of connecting the shield of a screened signal cable to chassis at one end only, leaving the other end open. This way no closed loop and no ground loop current forms through the shield. It is the preferred connection method for low-frequency analogue signals.
If the shield is grounded at both ends, the potential difference between the two ground points drives current through the shield; this current induces noise into the signal conductors. Connecting at one end opens the loop and maintains protection against the electric field.
- Which end: generally the end that the signal source or the measurement system takes as its reference is chosen. The chosen end must be labelled on the cable so that it is not changed at the next maintenance.
- Its limit: for signals above roughly 100 kHz, or when the cable length exceeds about one twentieth of the relevant wavelength, single-end connection is no longer sufficient; the shield is then connected at both ends or at multiple points.
- Open end: the ungrounded end is insulated and closed off with sleeving; it must not accidentally touch the chassis.
This rule is often skipped when running sensor and feedback cables. A shield connected to a terminal at both ends can give a worse result than having no shield at all. Marking on the wiring diagram which side the shield end goes to prevents installation errors.
The context in which this term is used: Installation, redundancy and field continuity