In another thread the set up is where two monitors share a ?? 500a shunt. Each monitor specifies 500a anyway. On the side of a shunt you get the little screw terminals (I have only seen the Trimetric 500a one) for the wires that go to the monitor. These read tiny amounts of ? voltage across the shunt to provide the readouts. Whatever. So, I am wondering----If you have two sets of these wires on the shunt's little side screws going to two monitors, will that mess up their readings by not having the right tiny amounts, because they are in parallel?It seems the two shunts agree on their readings, but that still leaves the possibility they are both equally wrong?

It won't affect either reading. The shunt is a very very low impedance and the monitors are a very high impedance. We use to call this a kelvin connection.

Hard to say without knowing the input impedance of the meters.If the inputs are buffered with an op amp before feeding the ADC you're likely OK sharing the shunt with multiple meters. On the other hand if the terminals for the meter input connect directly to an ADC, having two essentially in parallel across the shunt could skew the results.Test by running each meter solo with a number of large and small loads, and then repeat the same with both meters connected.

It will work fine. The digital meter itself doesn't create any load that will effect the other meter. In the old days of analog meters it would not work but the digital units have almost absurdly high impedance.

I don't know what an ADC is. The set-up in question is a Magnum inverter/charger with its monitor sharing a shunt with the Whizbang monitor going with a Midnite Kidd solar controller.

Analog Meter NYETDigital Meter DA

Two Monitors on One Shunt? | Good Sam Community

17 Replies

BFL13
Explorer II
Mar 14, 2018
OK, thanks all.
BB_TX
Nomad
Mar 14, 2018
If you had a very accurate measuring instrument down to several decimal points you could detect a slight difference simply due to the fact of paralleling another resistance. But that difference would be so small as to be inconsequential.
MEXICOWANDERER
Explorer
Mar 14, 2018
Analog Meter NYET

Digital Meter DA
BFL13
Explorer II
Mar 14, 2018
I don't know what an ADC is. The set-up in question is a Magnum inverter/charger with its monitor sharing a shunt with the Whizbang monitor going with a Midnite Kidd solar controller.
ScottG
Nomad
Mar 14, 2018
It will work fine. The digital meter itself doesn't create any load that will effect the other meter.
In the old days of analog meters it would not work but the digital units have almost absurdly high impedance.
GordonThree
Explorer
Mar 14, 2018
Hard to say without knowing the input impedance of the meters.

If the inputs are buffered with an op amp before feeding the ADC you're likely OK sharing the shunt with multiple meters. On the other hand if the terminals for the meter input connect directly to an ADC, having two essentially in parallel across the shunt could skew the results.

Test by running each meter solo with a number of large and small loads, and then repeat the same with both meters connected.
Roadpilot
Explorer
Mar 14, 2018
It won't affect either reading. The shunt is a very very low impedance and the monitors are a very high impedance. We use to call this a kelvin connection.

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Two Monitors on One Shunt?

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