Let's Get Amped Up....Ed Sherman

I'm not talking about a caffeine overdose here, but having a feel for how much amperage (electrical current)  is running through the wiring on your boat being pretty useful. You see when all is said and done amperage is the stuff that can cause really bad problems on board. Uncontrolled amperage is the stuff that causes electrical fires and shocks. So, knowing how to measure amps and what the readings you get can mean is good. In this installment I'll walk you through some of the basics related to amperage and how to measure it with your multi-meter.

Today, the only intelligent way to measure amperage is with a clamp-type meter; another reason I love the Blue Sea 8110 I've been mentioning in my meter posts here. The 8110 has a clamp and the ability to measure both AC and DC amperage (they are very different in terms of measurement) the range of measurement for both is 0.01-400 amps. This is a very useful range for boat use. On the low end, you can scout out elusive, really low level leakage current (I'll discuss that more in later installments) and up to 400 amps covers most equipment used. Things like anchor windlasses and bow thrusters, even starter motor current in many cases can be checked with this meter.

Using the amp clamp is easy, just clamp it around the wire you want to measure the current flow in. Just remember to set the meter for either AC or DC amps. Just turn the dial on the face of the meter to either the "A" with the wavy line under it for AC or the "A" with the straight line under it for DC. If the circuit is powered by your battery it is DC current, if it's powered by shore power or your generator or inverter its AC current. The face of the meter showing the A settings is shown below:

The other nuances you need to be aware of are that especially when reading low amperage values, you may need to zero out the guage. Looking at the above meter face you can see under the DC A setting, "zero" in yellow. With the rotary dial on this setting, just hit the yellow "select" button to zero out the meter before you attempt to take a reading. The other feature on this meter that can be useful is the "hold" button shown above. Sometimes amperage readings will jump around a bit while you are measuring them. If you are attempting to get a "peak" reading, or the highest value measured, just hit the hold button to lock on that maximum reading when it appears on the meters screen.

The only other question that comes up relative to using an amp clamp is the orientation on the wire you are checking. The clamp on the 8110 is quite helpful in this regard. On the side of the clamp you will see an embossed arrow. Also, on the face of the clamp, you will see a + sign. These indicate both the source of current and the direction of current flow. Orient the clamp so the + sign is toward the source of the current you are measuring, let's say the battery or pwoer distribution panel. The arrow is point toward the appliance that the wire is supplying, let's say the cabin light circuitry. This will determine whether or not the meter gives you a + or - amperage reading. This is important in cases where you may be trying to determine which direction the current is flowing, as there are some wires on your boat where it is possible for current to flow in both directions depending on whats going on in the circuit at the time of measurement. (More on that in a later installment.) The arrow and + sign are shown in the photo below. Oh, and don't worry if you get it backwards, it really won't hurt anything, it will just make things confusing when you really are trying to determine current direction.

One last thing. Make sure you turn the circuit on!

In my next installment, I'll tell you what is implied by various current and voltage measurements. This will be the beginning of making you an effective electrical trouble-shooter. In the meantime, HAPPY NEW YEAR! It's New Years Eve here. I'm taking tomorrow off, but I'll get the next installment in over the weekend.