Originally Posted by Steve LS
Sorry Im dense. Ammeter goes between negitive and ground ? With or without negitive terminal hooked to battery. (series lash up ) means nothing to me. I have volt meter but no ammeter laying around.
To measure current, you break the circuit and then use the ammeter to complete the circuit again. An ammeter presents a low resistance -- it'* basically a short circuit. So if you disconnected the negative terminal, you'd simply put the red (positive) lead of the ammeter on the disconnected (black) lead, and the black (negative) lead on the negative battery terminal. If you get the leads reversed, the meter will just read a negative current instead of a positive one.
This kind of connection is called "series," so named because all the current flowing through the lead you disconnected will now flow through the ammeter as well. It'* kind of like adding a train car to a train -- in essence, you're decoupling the train in the middle, dropping a car in the hole you just made, and reconnecting them together.
The other kind of connection is known as "parallel." This is how you'd measure battery voltage -- just place the red lead of the voltmeter on the positive terminal of the battery, and the black lead of the voltmeter on the negative terminal of the battery. No circuit breaks necessary.
So in general, you measure current in series and voltage in parallel. Be careful not to attempt to measure current in parallel, though, since an ammeter is a low resistance device -- and we know shorting out battery terminals is a bad thing.
(If you attempt to measure voltage in series, nothing bad will happen, as voltmeters are high-resistance devices -- but you probably won't get the result you're looking for.)