Husnen (Hus) Rupani:
I believe that the most important meter when it comes to safety is voltmeter. As the name suggests, it’s used to measure voltage. It’s also the safest meter to use because it’s not too easily damaged. In this video, I will show you how to measure a supply voltage, voltage drop across two components, and voltage generated by a permanent magnet generator. I’ll do these using an analog voltmeter, a digital non-auto-ranging voltmeter, and a digital auto-ranging voltmeter. Before we get started, you need to remember three things when using a voltmeter. First is to identify whether you’re measuring AC or DC and make a selection appropriately. Second, always stay below the maximum rated voltage of the meter. And the third voltmeter connection is always between two points. Let’s get started. Let’s measure supply voltage of this power supply using all three different voltmeters. We’ll start with the analog voltmeter. Since this is DC voltage, we’ll be in DC volts range. Always start with the highest voltage range possible. So in this case, thousand volts is the highest, so that’s where I will set my meter at.

Now that my meter is set to the highest voltage, I’m going to connect these probes to the supply. Positive goes to positive, positive goes to red, and the negative goes to black. At this stage, the power supply is off, so we’re not getting any reading, so let’s turn this on. And when we do, there is a very slight deflection. And it’s quite negligible because we’re trying to measure 12 volts at the range of thousand volts. So let’s drop it down one by one and see how that changes. Okay. Now we’re getting something. So at this scale where we’re seeing zero, 10, 20, 30, 40, 50, we can see how our measurement is showing about 12 volts, which is about right over there. Let’s measure the same supply voltage with a digital non-auto-ranging voltmeter. Now we’re set at AC volts at the moment and we need to change that to DC. We’ll start with the highest range, 600 volts. Connect this in the same way, red goes to red, black goes to black. And we can see 12 volts. Now we are at a very high scale, so we can drop that down.

Now this is giving us the most accurate reading, 12.21 volts. Let’s measure the supply voltage with a digital auto-ranging voltmeter. We’re already set up at volts and this has an option of AC and DC both. As you can see, we are set to DC at the moment. So let’s measure our voltage. And we’re getting 12.2 here as well, which is quite similar to what we had earlier. Now we have connected a circuit with this variable resistor in series with this lamp, which will allow us to control the brightness of this lamp through this. So let’s have a look at how the circuit will work first. So we’ve set it up to 20 volts, and this is the brightness of the lamp, which is the brightest at the moment. As I increase the resistance using the variable resistor, you can see how the lamp brightness is decreasing. What we need to do is we need to test the voltage across the lamp and the potential meter here or the variable resistor here as this value is changing and to see if the voltage will change.

Starting with our analog meter, we know that the maximum voltage there is 20, so we’ve set this up at 50, so we should be okay. Let’s start by measuring the voltage across the lamp first. Red goes to the positive side and black goes to the negative side. As we turn this on, we can see how our voltage is just around just less than 20 volts. And as I increase the resistance of this resistor, see what happens. The voltage is dropping, and at the same time, the lamp brightness is dropping as well. At this stage, I’m at the maximum resistance, and you can see it’s just around one volt or maybe even less. Let’s change that voltmeter to measuring the voltage across the variable resistor. And across that, we’ve got around 18 volts. And as I decrease the resistance, the voltage across the variable resistor also decreases, and the brightness of the lamp increases. Let’s do the same test with a digital non-auto-ranging multimeter, measuring the voltage across the lamp first at 19.92. As I increase the resistance, the voltage across the lamp decreases and the brightness decreases as well.

And at its maximum resistance, we get about 1.8, 1.7 volts across the lamp. That’s why it’s not working. Let’s measure the voltage across the variable resistor at the same time. We’re getting about 18.4. As we decrease the resistance on the variable resistor, you can see how the voltage is also decreasing, which means the voltage is increasing here and the brightness is increasing as well. In this setup, we are using this bottom power supply to power up this motor, which is coupled to this permanent magnet motor, which is now working as a generator, which is going to power up this lamp. So as this motor runs, this will generate voltage, which will power up this lamp. And our task is to measure voltage across this generator here and see how that changes as the speed of this motor changes. So let’s turn it on first and see what happens. Let’s measure the same output using a digital auto-ranging voltmeter.

There are many situations where a voltmeter is useful. Here are some examples. Measuring supply voltage or supply outlet voltage like batteries, generators, or socket outlets; measuring voltage drop cross components, wires, or contacts; identifying unexpected voltages like voltage across an equipment chassis and earth before working on it. And there you have it, how to use a voltmeter and its applications. Remember, a voltmeter can save your life. Always use one before working on an equipment or circuits. 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.