Imagine this: You wake up on a sunny Sunday morning, slowly step out of your bedroom and into your kitchen, place your toast in a toaster, and proceed to make your steaming hot cup of coffee. Sipping on your steamy beverage, you turn around to see that your toast hasn’t popped up yet.
A closer inspection shows that it’s not even warm. Disappointed, you settle for a bowl of cereal and unlock your phone. “My toaster won’t work”, you type on the internet, and the search engine provides you with a series of possible causes along with some instructions on how to fix them.
However, the problem isn’t solved yet; all of the articles that pop up entail using some instrument called a “multimeter,” but you’ve never heard of this strange instrument, let alone know how to use it. So what can you do? This is where we step in.
We will help you understand all about multimeters and how to use them without boring you with too many technical terms.
How do you use a multimeter to measure milliampere?
An ampere is a unit for current, and a milliampere is one-thousandth of an ampere. For many small LEDs, the current is measured in milli-amperes. So, how do you use a multimeter to measure milliampere? Let’s find out
- First things first, make sure that the appliance is unplugged. You don’t want to end up with an electrical shock, do you?
- The second step is to turn the meter on.
- Then place the right test leads or probes into the right connection. The black probe is usually placed in the connection labeled COM, which stands for common. While the other probe, which in the case of a Fluke digital multimeter is red, is placed in the connection right connection, in this case, we will connect to the input jack labeled ampere.
- Now you must be thinking, why connect to ampere and why not to the milliamp connection? This is because we don’t know how much current we’re going to be measuring, so by inserting the probe into the input jack for milliamps, we might cause the fuse to blow up. However, some digital multimeters may not have a separate connection for measuring milliamps; for better readability, it is recommended that you get one that does.
- Now, turn the switch to the correct measurement since we’re measuring current, so select the ampere option. Remember, we have not made the connection to the milliamp yet.
- You may change the current reading to AC or DC, depending on what you’re measuring.
- Now that we have ensured that the current is small enough to use the milliamp option, you may insert the red lead into the milliampere connection and rotate the selector switch to select the milliampere option.
- Ensure that the maximum range is higher than the reading that you expect, and later you can reduce the range to your suitability.
- To measure current, optimize the range for the best reading possible. Note down the reading.
Congratulations! You learned how to use the digital multimeter for measuring current. There’s just one last thing. Once you’re done measuring the current, as a precautionary measure, connect the probe to the voltage option and turn the switch to the maximum voltage range. This ensures safety if the meter is accidentally connected to a high voltage source when it is left set for current measurement.
So what is a multimeter? It is an instrument that measures current, resistance, and voltage and can therefore be used for electronic purposes. So if you can relate to the scenario mentioned above or if you simply like to tinker with stuff in your garage, this article is for you.
Why is a multimeter called a ‘multi’ meter? This is because, in addition to measuring current resistance and voltage, it can also measure capacitance, frequency, continuity, and temperature. So, essentially it is a ‘multi-purpose’ meter! See, that wasn’t too difficult, was it?
Whether it is ac or dc voltage and current or ac or dc resistance, the basic components of a digital multimeter are the same. After all the components of a circuit are well connected, what you need to do is to measure the current in amps or the voltage in volts.
Now that we’ve established what a multimeter is, let’s take things ahead and discuss analog and digital multimeters. Analog multimeters were used previously, and they involved a pointer that would show readings. Still, in this more technologically advanced world, digital multimeters are the go-to ones because they offer a numeric value, thus providing better readability, and the added cost-effectiveness is always a bonus! So if you ask me, I’d say digital multimeters are the way to go because when technology moves forward, why should you lag?
Essential components of a Digital Multimeter:
A fluke digital multimeter has the following components:
- A display that shows a numeric value.
- A dial or a selector switch
- Input jacks
A display is where the reading will show up. Although, the number of digits shown varies with the model. The greater number of digits shown, the greater is the accuracy. Below the display, you will see a dial as well as some buttons and some tiny holes, which we refer to as input jack. The number of input jacks may vary depending on the model. You can take advantage of these features to measure current.
Let’s face it. No one likes to be on the receiving end of inaccuracies, right? So how do you ensure that you get accurate results with a multimeter? All you need is some guidance.
If your reading differs from the actual value by more than 20%, then something is wrong somewhere and you should not continue taking measurements. So accuracy is one thing that you should care about before taking current measurements.
DC Voltage Accuracy
To test the DC voltage accuracy, take a DMM that is new and turn it on. A good multimeter will show 0.000 across its entire range of currents. Then you can just keep turning up the dial until you see some number.
Selecting the Right Digital Multimeter:
Before learning how to use the multimeter, you need to know how to select the suitable multimeter. Your selection would depend on the purpose for which you need the multimeter. If it is for basic electrical testing, you may require a different model, while for engineering purposes, some other model might be better suited to measure current, resistance, or any other specific parameter.
Fluke has made this step more accessible by providing suggestions regarding the best-suited model for each need. But before using this feature for taking current measurements, you need to learn another concept which is Category rating. There are four types of category ratings, CAT I, CAT II, CAT III, and CAT IV. These are ranked based on the kind of load that you are measuring. For instance, small appliances like the toaster oven fall under the CAT II rating, whereas outdoor meters fall under the CAT IV rating. These meters can withstand much higher voltage, occurring in surges.
SI Prefixes and Units
The numbers are given in numerical units of electrical voltage, current, and resistance are Volts (V), Amps (A), and Ohms respectively. Most details about the readings are there but the multimeter uses prefixes for important fractions and multiples of such quantities.
Choosing test probes
Most meters include pin and needle gauges to provide a pointy probe. Another alternative would be crocodile (alligators) probes which are spring-loaded with clips. These conductive probes are very useful because one or both probes can not be held in place directly by the fingers.
Multimeters have a range of test voltages and currents suitable for their particular range. These ranges are based on the meters’ CAT rating. Both analogs, as well as digital multimeters, have a certain voltage limit, beyond which they can’t function properly to produce accurate readings. If you use an incorrect or lower-range meter in order to check something that it’s rated for, then you are putting yourself at risk.
For current measurements, you need to make sure that you’re using the correct range. Most meters can only test 10 amps and anything above this will be inaccurate. This is also why a lot of Fluke multimeters also have an overload protection feature, which prevents them from being damaged during use. Check our Fluke 115 vs 117 comparisons.
With a multimeter, you can measure current accurately. Before that, it is important to select the right meter model. The accuracy of the readings depends on the quality and features of your multimeter. In addition to getting accurate readings, it is also essential to clean out any debris or dust gathered on your display, to insert the test leads in their appropriate port, and to make sure that you put your Fluke multimeter to rest while not using on the field to conserve battery life.
When all of the components of a circuit are well connected, and the unit for taking the current measurement is set to amps, your multimeter is all set to function properly and you can view the readings easily through the display. You
You can also use a clamp-on meter to view current readings.
Just like with voltage, amperage measurements are based on Ohm’s law which says that: Any current flow through a circuit is directly proportional to the potential difference across its ends or expressed as I=E/R. To measure this, all you need to do is find the potential difference across the ends of the circuit. Once you have found one end, move your multimeter to find out what resistance it measures, and then you can easily calculate how much current is flowing through it based on Ohm’s law.
So this makes resistance measurement the counterpart of the current measurement.
Resistance is the opposition to electrons flowing through a circuit, which you can measure with your multimeter. Just like you need to maintain safety while measuring voltage and amperage, it is also necessary that you do so for resistance measurements if you want to avoid getting injured by high amounts of heat produced by such activities.