Today, we're going to dive deep into one of the most essential Tools in our field, the digital multimeter. We're focusing exclusively on AC type measurements in this video, but it's important to know if you're measuring AC or alternating current or DC or direct current and choose the setting appropriately on your multimeter From volts to Mega, Ohms will cover each measure ment in detail, ensuring you have the knoow to get accurate readings every time. First, always use safety gear when working with energized electrical components. When testing live equipment with probes, always take the utmost care not to cross the probes to one another, touching ground, or other points in the equipment which can cause a short and possibly damage.

Let's start with resistance. Ohms is the measurement scale for resistance. We use the leads to measure between two points and the readout tells us how much electrical resistance there is between these two points in Ohms. Before measuring resistance, ensure your component is deenergized and always do an initial Ohm test from one meter lead to the other to confirm a solid path between the leads themselves.

In fact, this lead to lead. Ohm test is one of the first things I always do before using a multimeter and remember: Z Ohms signifies a closed circuit or a perfect path while infinite Ohms or O indicates an open circuit or no path the meter may show O it may show open or it may just show a series of dashes to indicate infinite Ohms or an open path. Let's use an example when oming a compressor. pay close attention to the range scale.

In the example of a compressor. when you're measuring using an N meter from terminal to terminal, a measurement in the Ohm scale is expected from terminal to ground. An O or infinite path or a path in the mega Ohm scale is expected. A path to ground from the terminals in the Ohm or the K Ohm scale is a sign of an undesired path or a short or grounded condition and is often due to a winding breakdown.

An O or infinite Oh path from terminal to terminal is a sign of an open winding or potentially an overload. In order for own measurements to be useful, you need to first know what the expected measurement should be. This can come from manufacturer specs comparing to another functional device or from past experience. Now let's talk about the Megaohm meter When detecting insulation breakdown, understand the difference between a high voltage megaohm test and a regular Ohm test.

The mega Ohm test can be more effective at finding insulation breakdown because it uses a higher voltage. When using a mega Ohm test, a general rule is to never exceed much more than double the max operating voltage, which is why you would use a 500 volt test on a 240 volt device and a 250 volt test on 120 volt device. Never apply a mega Ohm meter to sensitive controls always isol at and only measure on wiring and high voltage Motors and components. These Mega Ohm tests can help better understand current leakage to ground due to insulation breakdown over time, but are often unnecessary for residential equipment.

Many modern multimeters read well into the mega Ohm scale, even in the regular low voltage Ohm test. Another type of resistance test is known as the continuity or ring out tests. and that's simply to confirm if a circuit is open or closed closed, not the exact resistance value. Keep in mind the range that a meter will ring out May Vary from meter to meter when it rings, that's just signifying a closed circuit or a quote.

unquote good path, and when it does not, it's signifying an open circuit. You would often use this continuity test to test conductors or switches to confirm whether they are open or closed. An ammeter or Amp clamp uses electromagnetic force from around the wire. It's measuring to measure the current moving Through the Wire This test only works when the component is energized and operational.

For this reason, Amp measurement is primarily used to determine operational functionality. not to figure out why something isn't working. When measuring amps, make sure to position the wire in the right part of the clamp jaw and always remember only one wire at a time time. Also, be careful, ammeters become less accurate at lower current measurements, which is why many TXS will misdiagnose smaller Motors like condenser fan motors as drawing High amperage because they are lower current devices and therefore the measurement is more susceptible to interference from other conductors and devices and meter andaccuracy.

When using a voltage meter, you're measuring electrical pressure between the two points that you have the leads connected to. If you put both probes on the same point, it will read zero no matter how high that voltage might be in reference to ground or neutral. This is why you must always think carefully about exactly where you're placing the probes, that you're making good contact with the probe to the connection point and what that means. One of the most common mistakes is interpreting zero volts across a switch or a connction ction as an open.

If a circuit is energized and a switch is closed, there will be Z volts across the switch because there is no pressure drop or voltage change across a closed switch. When the switch is open, that's when you may see voltage across it. This is why generally speaking, you'll put one lead on the opposite side of the circuit either neutral, the other side of 240 volt or 3-ph power, or in some cases to ground and you will walk through the circuit with your other high voltage lead, measuring that pressure drop or voltage difference as you go through the circuit. For the most effective voltage measurements, take them under load.

meaning with the component running, this lets you observe any potential operational voltage drop Only do this when it can be done safely. Keep in mind, modern multimeters often feature Auto ranging meaning they change AR range automatically. Always check to ensure that you're on the correct scale for accurate readings. A very common issue is thinking of Voltag is present just because the meter has Auto ranged to a tiny measurement like Molts.

Watch the onscreen scale symbols. capacitance or the ability to store and release current from a capacitor is measured in Farads. A Farad is a very large capacitance scale, so we use capacitors and and we test in the Microfarad scale. Typically, we simply power down the equipment, remove the connection, discharge the capacitor, and measure from one side of the capacitor to the other with the leads in the capacitance scale and note the measurement like everything else.

when testing a capacitor, Precision matters. If you're not on the right scale, your readings can be misleading. If you think you're seeing microfarads when you're actually measuring Pico farads, you can easily be confused, used, and come to the conclusion that a capacitor is functional when it actually isn't in HVAC Measuring microamps is a useful test when testing gas. Appliance Flame rectifiers.

This requires wiring the meter leads in series with the flame rod and furnace control. as shown here, Do not confuse microamps with a regular Amp scale. It's generally a separate setting on the meter and where amperage uses the Amp clamp. Microamps is an in series connection using the meter leads.

Whether it's Microfarads, Amps, Ohms, or Volts. Understanding the measurement and the respective scale is really important. Remember, mastering your multimeter is not just getting numbers. You're ensuring safety and efficiency on your job and ultimately coming to the correct diag ostic conclusions.

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