# May i know why the 100A Display Digital Current and Voltage Meter came with a shunt bar what is the purpose ???

#### Alex1700

Joined Jan 12, 2020
105

Joined Jul 18, 2013
27,663
Shunt bar = shunt resistance

#### crutschow

Joined Mar 14, 2008
32,933
A standard ammeter measures current by measuring the voltage across a small resistance in series with the current being measured.
The shunt is that resistor.
.

#### sdowney717

Joined Jul 18, 2012
711
The shunt inline with the negative wire creates a voltage and that voltage increases with increasing current flow, typically 75mv at its max rating that the LED meter can read and interpret as amperage in the wire. You just can not send full current thru those little meters, so you have to use a shunt. I just bought a 500 amp volt and amp meter with shunt, I plan to use in my boat to monitor the house bank use, to include the DC inverter. I figure 500 amps would cover the max current it would ever experience.

here is that meter and shunt, not a bad deal I think .

DC 200V 500A + Shunt Voltage Current Meter Digital LED Voltmeter Ammeter 12V 24V | eBay

Joined Jul 18, 2013
27,663
The shunt inline with the negative wire creates a voltage
Why the Neg wire specifically?, either neg or pos will work!
Unless that model is designed for it specifically?

#### sdowney717

Joined Jul 18, 2012
711
Why the Neg wire specifically?, either neg or pos will work!
Unless that model is designed for it specifically?
Dont know, but the instructions say put it in the negative return to the battery.

#### sdowney717

Joined Jul 18, 2012
711
Can someone look at the 2 wiring diagrams and tell me if either one will work for a single battery being the source of power and the measured source of power?
They describe connecting it 2 different ways. One is buck circuit or module for meter power using a separate power source from the measured battery?

Also for the diagram would disconnecting the black wire from the shunt, turn the meter off?
See, right now I have 2 volt only meters, 2 banks. Each positive wire goes to its own meter. Then the negative wire, I put a switch, negatives on both banks join together to a common point. So with the one switch I can turn off both meters and yet each meter reads volts from each bank. I am thinking of using a volt-amp meter for the house bank, but would like the switch to still turn off and on both meters, the starter bank would remain a voltmeter only. House bank would become a volt - amp meter.