Husnen Rupani:
When voltage is applied to an equipment, current starts to flow in the circuit, and voltage and current together make it operate. Voltage is usually fixed, but the current changes as the demand from the equipment changes. This is why it is important to be able to measure current, and the instrument used for this is called an ammeter. There are two main types of handheld ammeters, an inline ammeter and a clamp on ammeter. We will use both types of ammeters to measure current going through a lamp, a variable resistor, and a DC motor. Before you use an ammeter, there are three main considerations. First, identify whether you are measuring AC or DC and choose the setting appropriately. Second, before connecting an inline ammeter, it should be set to the highest range and the supply to the equipment should be isolated. Third, identify the type of ammeter to determine its connection method.

Let’s get started. Since we know that we’re going to measure DC, we need to choose our ammeter options. We have two options here, ammeter AC and ammeter DC. So 10 amps is our highest possible range. Now let’s connect the circuit. Before connecting the circuit, the switch should be off. That means the power is isolated. That way there’s no current flowing in the circuit. First of all, our current needs to go from the positive side of our DC supply into the meter. From the meter, it will go to the load, and from the load, it will return to the supply. So the current path will be current coming out of here, going inside the meter and coming out of the meter, going to the load, and from the load returning to the supply. This is the reason why this type of meter is called an inline ammeter.

Let’s turn this meter on. Right now we have no current because the switch is off. Let’s turn the switch on and see how much current we get. We can see that we’re getting around 1.01 amp, so just about one amp of current. While we have the current going through this ammeter and the lamp is on, let’s also use our clamp on ammeter. This is our clamp on ammeter AC and DC both. If I go to my setting of 40 amps, since I already know the current will be roughly one amp, and force this wire to go through this loop here, then I’ll be able to measure the current that is going through that circuit. So you can see how we’ve got one amp there and about 1.05. So there is a little bit of error there. You can see how for an inline ammeter, I had to disconnect the circuit and force it through the meter. For clamp on ammeter, all I needed was the wire.

Now there is a trick with this clamp on ammeter. Usually when you install the cables, they’re not really single wires. They’re multiple cables. There’s active and neutral, both in there. So if I was to take the current that is going inside and outside at the same time, see what happens. I get no current whatsoever. That’s because the current that’s going in from here the magnetic field that this current is generating is canceling out the magnetic field from this one. Since both currents are the same, the net result is zero. So basically a clamp on ammeter measures the magnetic field of the current and decides how much to display. Now that’s for DC. For AC, it uses a mutual inductance, which is another topic.

Let’s turn this circuit off. Let’s change our circuit to measure the current going through this variable resistor. So all I need to do in this case is change the load connection to here. So now the current path is current will come out from the power supply, go into the meter from the meter, go into the variable resistor, and from the variable resistor, go back to the supply. That completes the circuit. Okay. Turning this on, we’re getting about 0.64 amp of current. Now, since it’s a variable resistor, I should be able to control the current by changing the resistance. So if I increase the resistance, you can see how the current is decreasing, and if I decrease the resistance, you can see how the current is also increasing. Let’s at the same time measure the current using our clamp on ammeter that we already have. Let’s use this wire. If I was to change the resistance, you will see that both meters will respond approximately at the same time.

Let’s change our circuit yet again to power up this DC permanent magnet motor. The output will be going to the motor. So if we’re looking at the circuit again, the current comes out of the power supply, goes into the ammeter, comes out of the ammeter, goes to the motor, comes out from the motor and returns to the supply. That’s my complete circuit. Let’s turn it on, see what happens. So right at this stage, this motor is drawing 0.5 of an amp, or 500 milliamps. Let’s use our clamp on ammeter to measure that current. We’re getting about 0.57 instead of 0.48. So there is some error there. Now, what’s interesting to look at is what will happen to the current when this motor is under load. I’m going to put load on this motor by just slowing it down manually. As you can see, as there is more load, more current is drawn by the motor. If the load reduces, then the current drops down as well.

There are many situations where an ammeter is useful. Here are some examples. Fault-finding circuits using a clamp on ammeter for safety, testing the current requirement of an equipment like a motor under changing loads, identifying maximum demand of an installation, and many more. There you have it. How to use an ammeter, safety considerations, and its applications. If you found this video informative, please like it, and if you know someone who can benefit from it, please share it. Thanks for watching.