Rudimentary, determine what is neg and pos

[tomjasz]

I have the two batteries listed in my sig. How do I determine which is neg or pos lead. My multimeter show I - minus sign in one configuration with the meter.
Sorry but I'm learning with no mentor.

 

[Punx0r]

If the voltage reading on your meter is negative (-) then you have connected backwards. When the reading is positive then then red meter test lead corresponds to the positive wire you are testing (assuming the meter leads are plugged into the correct sockets on the meter...).

 

[mark5]

Below is one of many Youtube videos on how to use a multimeter. Checking DC voltage is at 1:05-2:20 with a mention of checking polarity at 1:50. A minus sign at 9 o'clock shows on his meter LCD to indicate reverse polarity if red and black are improperly crossed. You can practice with an AAA, AA, or other small battery as a reference to see what display will show.

[youtube]bF3OyQ3HwfU[/youtube]

 

[dogman dan]

For a noob learning the multimeter, do take care that the red lead and black lead are plugged into the right sockets.

Of course you know how I learned that one. One fried charger later.

 

[Punx0r]

I reckon the following are the first two mistakes most of us make when using a multimeter:

1) taking a resistance measurement, then trying to take a voltage measurement without changing the dial back to the voltage setting - you can't measure the resistance of a live circuit and can damage the meter.

2) taking a current reading, then trying to take a voltage reading without remember to switch the positive test lead to the correct socket. This shorts out what you're trying to measure through the meter, blowing the tips off the test probes and either blowing a fuse in the meter, or damaging it if it's unfused.

 

[spinningmagnets]

get a D cell or AA flashlight battery that is from around your house. They are clearly labeled. Take a 1.5V reading on the small cell, then see what the screen reads out.

Make sure to re-set the range if the E-bike battery is 36V-48V. The 1.5V battery would be read on the 0V-20V range.

 

[tomjasz]

Thanks ALL. Got it! Another giant step forward!(well big for me..)