ammeter shunt placement

Thread Starter

bwanna

Joined Nov 19, 2012
15
So how does the power source tie to the bus?
That's a good question. The bus is actually only in the neg side. The power source has a single point of generation and then splits out to each of the subsystems. The power source's ground side connects to the Neg bus.

Because of this, I'd be concerned with simply placing the shunt between the power source Neg and the Bus, for fear of other subsystems bypassing the shunt (by nature of directly being connected to the bus elsewhere.)
 

Thread Starter

bwanna

Joined Nov 19, 2012
15
This may be the one OP has.
http://www.ebay.com/itm/DC-50A-Red-LED-Digital-AMP-Ammeter-Panel-Meter-With-Current-Shunt-/110956430319?pt=LH_DefaultDomain_0&hash=item19d584c3ef

Has to be wired in low side. IMO

Now this one, I don't know?
http://www.ebay.com/itm/Mini-Red-LED-DC-Amp-Current-Meter-Ammeter-0-50A-No-need-Isolated-Power-C27-/180907264399?pt=LH_DefaultDomain_0&hash=item2a1ee9c98f

Specifies,"0-50A-No-need-Isolated-Power-This meter can be powered by the same source being measured(DC4.5-28V)., "
Good candidate to use with the same shunt.

Yet diagram shows connection in the low side?

Is it or is it not isolated?
These sellers generally don't know squat about what they sell.:(

I agree with your observations... it seems some of these are designed in a way that doesn't allow sharing V+
 

Thread Starter

bwanna

Joined Nov 19, 2012
15
I've ordered a dc/dc isolator to power just the meter. Should be here by weekend. I'll post an update.
 
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inwo

Joined Nov 7, 2013
2,416
I'm not convinced. As we don't have the details.

If this is measuring battery current, either high side or low side, and battery is sometimes being charged, it needs to read positive and negative.

If it is reading current to the load, and charging circuit goes direct to battery, then it should be ok. But then whats the point of the meter?
 

Thread Starter

bwanna

Joined Nov 19, 2012
15
I'm not convinced. As we don't have the details.

If this is measuring battery current, either high side or low side, and battery is sometimes being charged, it needs to read positive and negative.

If it is reading current to the load, and charging circuit goes direct to battery, then it should be ok. But then whats the point of the meter?
I agree that placing the shunt in line with the batter (pos or neg) will only read what's happening with the battery. Placing the shunt in line with the generator (pos or neg) will only read what's happening with that.

Since there are multiple connections for the neg (hence the use of the term 'bus'), my test will be to place the shunt in line with the generator pos using a DC/DC isolator to power the meter. With this approach I recognize that I'll only be measuring what the generator is doing and foregoing what is happening with the battery.

To know what's happening to the battery, I'm going to design a simple Charge/Discharge Indicator circuit that turns on an led (Green/Red) corresponding to the status, respectively.

Between these two, I'll be able to know fairly well what the draw is on the two power sources.

I found this. Seems like it does what I want regarding the Charge/Discharge indicator of the battery:
 

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MrChips

Joined Oct 2, 2009
19,160
The OP wants to know the pros and cons of placing the current sense meter on the +ve side or -ve side of the battery.

The OP would also wish to know whether the battery is charging or discharging.

A center-zero ammeter as shown above placed on either side of the battery will provide the OP with the information he seeks.
 
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Thread Starter

bwanna

Joined Nov 19, 2012
15
The OP wants to know the pros and cons of placing the current sense meter on the +ve side or -ve side of the battery.

The OP would also wish to know whether the battery is charging or discharging.

A center-zero ammeter as shown above placed on either side of the battery will provide the OP with the information he seeks.


Agreed. This would be nice. Do you happened to know where these are available in a digital led read out? I haven't found any. That's what prompted me to ask the original question since I had to choose.

And this has nothing to do with automobiles! Lol
 
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