# meter common ground issue

#### stuck in language barrier

Joined Sep 9, 2011
4
I have purchased lcd meters voltmeter plus ammeters 6/24 volt input and have been told by manufacturer that 2 meters can be run in the same circuit
but if any more than 2 meters share the same circuit it will require separate power supplies due to (im told)a shared ground issue and if not could damage the meters..As I am running two volt meters and two ammeters <25ma each
or <50ma when using backlight option i am looking at a meanwell power supply (isolated) sd 25a 12 power supply (2) to take care of meter problems..am i going the right way? The information I have gotten (due to language barrier) is not clear..Can someone clear this up for me? I have installed many meters (automotive) but have not encountered this.....these meters are being used in a solar monitoring setup 12 volt system....thank you

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#### SgtWookie

Joined Jul 17, 2007
22,221
That Meanwell supply you are considering is maximum overkill for your LCD meters. It will be a large drain on your 12v solar system.

We have no idea where you are, as you have not put that information into your profile, so it is difficult to know what supplier to suggest. You can click on the "User CP" link on the menu, fill in your Location information, and then click the "Save" button at the bottom. Just your Country is usually sufficient; if you are in a very large country, then adding your time zone or nearest large city is helpful.

You should look for isolated DC-DC converters with input and output ranges that you have available/need. Since you have provided very little information on the meters, we don't know what supply voltage they require.

If you operate the meters continuously, they will be a drain on your solar system.

#### stuck in language barrier

Joined Sep 9, 2011
4
the meters in question have a built in power supply capable of using 6 to 24 volts dc (powered meter input) volt meter range 0 to 50 volts..the ammeters also are the same...i can order what i may need from jameco...I am surprised that i cant just wire these up ...they offer 3 styles (input power)..5 volts fixed..6 to 24 volts..and 25 to 240 ac and dc..the latter they claim is the only one that can be used in multiples...Does this sound (what they are saying) to be a real case scenario?I would prefer not to have to build a power supply myself it will be too difficult in the field..but the power supply must be capable of dealing with the voltage variance..ARE THESE GUYS BLOWING Smoke ?Is there really a possibility that these can be damaged wire up like that ?In hakie takkie english something was mumbled about common ground issues.. Is this real? Is there a possiblility it can harm these meters? I am looking for the easiest fix if possible.. thank you for your reply

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Joined Dec 26, 2010
2,148
I would take the warnings given to you by the suppliers seriously, despite the fact that they are foreigners who speak poor English.

If meters share a common power supply source, then unless they contain internal isolating barriers there can be problems if their inputs are taken to different potentials. There can even be issues when one meter is used to measure the same supply that it is being powered from - not necessarily but it is possible.

The third AC/DC power supply option seems likely to be a switched-mode system providing isolation, whereas the lower voltage DC input options may not do so. If you only have available a DC supply at less than 25V, then you should provide your own isolation, and I would reiterate SgtWookie's advice to use appropriately rated isolating DC-DC converters for this.

#### SgtWookie

Joined Jul 17, 2007
22,221
You can purchase small isolated DC-DC converters that are really quite efficient, but they will be in the neighborhood of $6-$15 USD each. If you would tell us where you are, like I asked in my first reply, we might be able to find something suitable for you to purchase that simply needs to be installed. If you don't want to purchase isolated DC-DC supplies, you might consider using batteries, but they will need to be replaced periodically.

You really would not want to build something like that in the field.