I want to be able to read the amps of my solar panels.

Thread Starter

twister007

Joined Feb 29, 2012
81
I just finished building a 60 amp solar panel voltage controller and I would like to be able to measure the amperage. With the built in volt meter. I can insert a 1 ohm resistor in series but that would waste power and create heat. I have a old 120 v transformer and I was wondering if I removed the winding and passed one output of the voltage controller thru the winding, would I pick up any kind of voltage that would make sense? The controler is pure DC. The volt meter reads down to .01.
 

DickCappels

Joined Aug 21, 2008
10,152
The t transformer only works with AC. If you are using DC, the classic solution it to use a lower value shunt resistor. Instead of 1 ohm you might want to try .01 ohms, or as (I just noticed) 0.1 ohms. I think you get the idea.
 

ElectricSpidey

Joined Dec 2, 2017
2,758
Be sure if you shunt that meter you don't reconnect it as a voltmeter. (Parallel)

Be very sure to reconnect it in series.

Also note, if that meter is an electronic built in meter without an isolated power supply it may not even be possible to rewire as an Ammeter.
 
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Thread Starter

twister007

Joined Feb 29, 2012
81
The t transformer only works with AC. If you are using DC, the classic solution it to use a lower value shunt resistor. Instead of 1 ohm you might want to try .01 ohms, or as (I just noticed) 0.1 ohms. I think you get the idea.
Thanks! A coil around a wire with DC flowing thru it, won't pick up a voltage? How do DC clamp on meters work?
 

MisterBill2

Joined Jan 23, 2018
18,176
OK, and if the current that the TS wants to measure is AC, 50 or 60hz, the transformer is avalid concept, but calibration may be a challenge. If the current is DCthen a commercial ammeter shunt is the simple way to go. Not certain what the issue about the high impedance meter is, I have used high resistance digital meters with hundred amp shunts only producing 100 millivolts at 100 amps.
The TS did not provide enough information.
 

MrChips

Joined Oct 2, 2009
30,715
This meter is a digital volt meter with an internal resistance of a 100,000 ohms. I can't use a shunt resistor.
Why not?
Use a 0.1Ω resistor in series between the solar panel and the load.
Measure the voltage across the resistor.
1V reading means 10A current.
 

Thread Starter

twister007

Joined Feb 29, 2012
81
Be sure if you shunt that meter you don't reconnect it as a voltmeter. (Parallel)

Be very sure to reconnect it in series.

Also note, if that meter is an electronic built in meter without an isolated power supply it may not even be possible to rewire as an Ammeter.
Thanks, the meter and digital display uses 5 volts from the controller. It a volt meter only.
 

crutschow

Joined Mar 14, 2008
34,285
A coil around a wire with DC flowing thru it, won't pick up a voltage?
Nope.
Only AC current can be picked up that way.
How do DC clamp on meters work?
They typically use a Hall-effect device which generates a voltage in response to a DC magnetic field.

For best accuracy you could use a shunt resistor designed for measuring current such as this 75mV shunt.
It measures 75mV across it with 60A through it (1.25mV per Amp).
You can use any analog or digital DC voltmeter of the appropriate sensitivity to read thus voltage.

You might also consider using a Hall-effect sensor if you want no-contact sensing.
 

Thread Starter

twister007

Joined Feb 29, 2012
81
Nope.
Only AC current can be picked up that way.
They typically use a Hall-effect device which generates a voltage in response to a DC magnetic field.

For best accuracy you could use a shunt resistor designed for measuring current such as this 75mV shunt.
It measures 75mV across it with 60A through it (1.25mV per Amp).
You can use any analog or digital DC voltmeter of the appropriate sensitivity to read thus voltage.

You might also consider using a Hall-effect sensor if you want no-contact sensing.
Thanks for saving me a lot of useless experiments! If I made one of the wires from the controller into a coil and put a hall effect sensor in the middle, would that put out a voltage?
 
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