| ??? 03/02/05 06:38 Read: times |
#88842 - grounding Responding to: ???'s previous message |
Per Guldmann said:
I am in doubt, how to connect my digital ground to the chasisground. This device is a class 1 thing - its made of iron, and connected to mains, and not doubleisolated, so it should have its chassis connected to the mains earth (with a yellow/green wire) for safety reasons.
For screening reasons, I would prefer to connect my digital ground to the chassis, but I dont want all the trash from the mains earth. I the analog world, one would do it through something like 50 ohm in series with some 10 nF to get the screening effect and break the ground loop. But I am not so shure about "good engeneering practice" when it comes to the digital domain. When you say "digital ground," are you referring to cable shields or the digital circuit reference? If the latter, then you should connect the circuit common to the chassis at one point. Otherwise, there could be weird coupling due to the chassis being at one potential and your circuit common floating with respect to it. If the former, then I ask: are the signals in your cables single-ended or differential? If differential, you should simply tie the shields to the chassis. Remember that the cable shield is literally an extension of the chassis. Sure, you may have ground differences between Box A and Box B, but that ground current ends up being drained to the chassis and NOT to the circuit reference (which is also, unfortunately, called "ground"). Single-ended cables are always a problem because the signal return current is mixed with the shield and ground loops are a problem. You can't disconnect the shield at one end or the other because you end up breaking the circuit. -a |
| Topic | Author | Date |
| To ground or not to ground? | 01/01/70 00:00 | |
| Grounding | 01/01/70 00:00 | |
| Universal garbage sink ? | 01/01/70 00:00 | |
| Decrease of earth impedance | 01/01/70 00:00 | |
| jumping ground | 01/01/70 00:00 | |
| It's also a safety issue! | 01/01/70 00:00 | |
grounding | 01/01/70 00:00 |