Negative Output?

[CapnCrunch]

In checking the output from my solar panels, I sometimes get temporary negative amp readings. Is there a problem or is my multimeter faulty?

[RaymondR]

It happens if you plug the leads into the multimeter with the red lead in the black hole??

[wholybee]

How are you measuring Amps with your multimeter? What wires are you connecting where? Knowing how and where you are making the measurement will make a difference.

If a blocking diode is missing or shorted it is possible for current to flow backwards into the panel.

[CapnCrunch]

Originally Posted by wholybee

How are you measuring Amps with your multimeter? What wires are you connecting where? Knowing how and where you are making the measurement will make a difference.

If a blocking diode is missing or shorted it is possible for current to flow backwards into the panel.

I am using a clamp-type meter on the positive wire from the panel to the controller.

There is no blocking diode installed. I was under the impression that these were built into the panel.

[claptrap]

If you happen to flip the direction of the clamp meter, you will read negative current as well.

[GordMay]

Originally Posted by claptrap

If you happen to flip the direction of the clamp meter, you will read negative current as well.

When using a DC clamp meter the sign will change from positive to negative, if you reverse the orientation of the clamp, on the wire.
Many clamp meters now have an indicating arrow.
When the arrow points to the load, the sign will be positive, and when the arrow points to the power source [battery], the sign will be negative.