Do you need to? We want them all to go to the earth eventually right?
On 3/31/2016 7:38 PM, Jaime Solorza wrote:
Are you isolating your DC and AC grounds?
On Mar 31, 2016 4:44 PM, "Ken Hohhof" <[email protected]
<mailto:[email protected]>> wrote:
If the two pieces of metal are not connected together, like if one
of them is floating except for stray high resistance paths to
ground, then I wouldn’t pay much attention to the voltmeter
reading. Especially if you are using a high impedance digital meter.
Or if they are connected via a wire carrying high current, 0.1
volt may not mean much. If you have 10 amps flowing through a
wire with 0.01 ohms resistance, there’s your 0.1 volt.
If that second piece of metal is grounded to your common ground
point with a wire that should not be carrying any current, then I
might worry about the 0.1 volt. You might have a ground loop.
Are you seeing a DC or AC voltage?
*From:* George Skorup <mailto:[email protected]>
*Sent:* Thursday, March 31, 2016 5:32 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Another ground question
That's what i was going to say. If it's a cheap meter, don't worry
about it. Bond everything and you should be fine.
On 3/31/2016 5:27 PM, Chuck McCown wrote:
Depends on the meter. Does the meter read 0.0 when the leads are
shorted together?
Some meters have some random fluctuations in the least
significant digit all the time.
*From:* Josh Baird <mailto:[email protected]>
*Sent:* Thursday, March 31, 2016 3:24 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* [AFMUG] Another ground question
I'm working on a new DC enclosure (steel 19" rackmount cabinet).
When using a DC volt meter, and putting the 'red' lead on a
common ground point (my ground bus, a metal rack rail, etc), and
the 'black' lead on something metal, I'm seeing ~0.1V.
I'm assuming this is bad. On the bench currently, I have the AC
ground connected to my PSU. I have all other devices (switch,
surge suppressors, rack rails, etc) tied to a common ground that
isn't yet connected to earth. My PSU and power distribution is
on a metal DIN rail which in turn is mounted to the metal rack
rails.
Should I be concerned with this? As much as I try (or not), I
still have trouble wrapping my head around ground/ground
potential/etc.
Josh
