I bought a voltmeter... does it work?

[Pinesal]

Hi guys. I bought one of these voltmeters to monitor my battery pack.

https://www.amazon.com/SMAKN%C2%AE-Waterproof-Digital-Voltmeter-0-100V/dp/B00K3GHFCM/ref=cm_cd_al_qh_dp_t

It came with four wires attacked. Red, black, white and black.

I thought I would just attacked the red to the positive on the battery and black to the negative and the LCD display comes on but it displays 0.0.

I used a multimeter to double check the batter and it should read 13.5v. So is there more to the voltmeter than I thought? What are the extra white and black wire for?


EDIT: I figured it out. The the red and black apparently power the LCD. The white and black are what actually read the voltages. Leaving this up for the next guy.

 

[boisrondevens]

The white/black wires also need to be hooked to the thing being measured. If measuring your battery voltage, hook the white wire to the battery + and the black to battery -.

 

[dogman dan]

What you needed looks identical, but has just two wires.