Voltmeter

VD September 09 2021

A voltmeter is a device that measures the voltage in a circuit, while a multimeter typically measures current and resistance. However, some multimeters also measure voltage.

What Does a Voltmeter Do?

A voltmeter measures the voltage between two points in an electric circuit. The reading is obtained by averaging the difference of potential between the two points.

Types of Voltmeters

There are three main types of voltmeters: analog, digital, and microprocessor-based.

  • Analog voltmeters use an analog meter movement for measurement. They are typically designed with a moving pointer that shows the measured voltage on a scale.
  • Digital voltmeters use an LED or LCD display to show measurements in digital format.
  • Microprocessor-based voltmeters (or electronic digital voltmeter) contain an analog-to-digital converter circuit, which is used to convert the analog signal to a digital signal, and then the digital voltmeter converts that signal into a display or numeric representation.

How to Use a Volmeter

AC Output

A voltmeter can be used to measure AC voltage by changing the selector switch. To change the selector switch on a  voltmeter  to AC, find your AC voltage setting on the selector dial as shown in Figure 1. The scale for this setting is typically from 100V or 250V. In my meter it's 250V. You can see this setting in the upper right-hand corner of the dial in Figure 1.

WARNING: SAFETY FIRST! - Only Use a Voltmeter with Power OFF

Before you start, be sure to switch your voltmeter to AC and turn it off so that there is no voltage inside the meter. This is a safety precaution to avoid shock or electrocution.

Connect the Black Lead

Find the black lead on your voltmeter and connect it to the COM jack located at the bottom of your voltmeter in Figure 1. The COM jack stands for common, which in this case means that it's ground, or negative voltage.

Connect the Red Lead

Connect the red lead to whatever you want to measure voltage on. This can be done with a continuity test, as shown in section 3. The scale for this setting is typically from 100V or 250V. In my meter it's 250V as seen in Figure 2. You can see this setting in the upper right-hand corner of the dial in Figure 1.

Why It Matters: Why this Setting Is Important

So why is it important to set your meter to AC and what does this setting do? The answer to this question can be found by thinking about how a measuring device (or voltmeter) works.

A voltmeter is a current limiting device. It uses its internal resistance to limit the current through it, thus providing accurate voltage measurements. The reason that it's important to set your meter to AC is because most electronic devices are powered by AC - not DC! This means that they use alternating current (AC), which reverses direction many times each second, as opposed to DC, which is direct current and stays the same direction. This means that if you set your meter to measure DC voltage and then connect it to a device that uses AC voltage, you'll get incorrect readings because the voltmeter will measure a lower voltage than what's actually there. So always make sure that you're setting your meter to the proper voltage.

Testing Batterie

To test a battery, you have to be sure that the meter is set to measure DC voltage. Look at the dial on your voltmeter and find where it says "DCV" or "DC Voltage". If it doesn't say this, then switch the setting using the selector dial as shown in Figure 1. This is probably found at the lowest or left-most setting on your meter.

Once you have set your meter to DC, connect the red lead to the battery's "+" positive terminal and the black lead to its "-" negative terminal. If necessary, use a continuity test as described in section 3 to find which are your "+" and "-" terminals.

How to measure current

To measure current, you need to connect it in series with a load. The port that the probes are inserted into should be set appropriately for measuring amps on your multimeter. If not done correctly, this can damage or blow out the internal fuse of your meter and render it useless!

How Most People Fry Their Multimeter

There are many times in which people fry their multimeters when trying to measure current. Typically, this happens when they try measuring the amps without a load on the circuit. They will set up their meter with red probe tip plugged into socket marked 10A and then stick it directly into an outlet or place probes parallel to any other high-current power source that could potentially blow your meter out if you apply 0 ohms of resistance onto them like what happened here! Always make sure to use caution while checking for currents by placing meters in series (one after another) with loads.

To Sum Up

In conclusion to this article, always make sure you're setting your meter to the proper voltage and use caution when checking for currents. Always remember that using a voltmeter requires you to know what you're doing! If not done properly, you can fry your multimeter or even worse, electrocute yourself! Have fun and be safe while learning!