Accelerometer Frequently Asked Questions
Question number FAQ-1364
How to use the grounding switch (Case/Float) in the AU series
By setting the "Grounding Switch" to <CASE>, the signal common is connected to the AU series' ground terminal and enclosure. Normally, this mode is used to stabilize the internal reference potential and allow external noise (including noise coming through cables) (N) to escape to ground for stability. However, in cases such as (1) to (4) below, switching to <FLOAT> and disconnecting the internal circuit from the case may reduce the likelihood of noise being superimposed on the output signal by eliminating noise paths and loops.
| （1） | If grounding is applied, but noise from other devices flows in and is superimposed on the AU's output, |
| （2） | When grounding the case, a ground loop can be created, resulting in noise. |
| （3） | If inductive noise is present on the frame or table to which the AU is attached, and this noise is transmitted through the AU case to the signal, |
| （4） | If the frame or table to which the AU is attached has an electrical potential and is connected to the signal common, a short circuit or other malfunction may occur at the connection point. |
In short, you should use the FLOAT setting on the grounding switch if there is an electrical potential at the mounting rack or installation location, or if the output signal contains noise and setting the switch to FLOAT reduces the noise. However, in this case, the device will be more susceptible to electromagnetic noise from cables, etc., so the choice between CASE and FLOAT should be made on a case-by-case basis.
Last updated: 2007-08-20