Hello, beginners, this is a tutorial about How to Use a Multimeter. On the Internet, you’ll find more tutorials on this topic. Yes, they are well explained but not to-the -point. If you just want to get started in using a multimeter without digging into too deep and not willing to read tons of data right now, then this the best article for you. Every aspect of this topic is covered here without bombarding the readers’ mind with excessive information. let’s go:
First of all, we need to know what a Multimeter is. So,
A multimeter is a necessary tool to measure current, voltage, resistance and some other parameters. Some high-end multimeter can also measure temperature, capacitance, and frequency.
As you can see in the image, it consists of 1 digital display, 1 knob (Rotary Switch) to select a parameter and its range of value, a socket to measure transistor parameters, and 3 separate ports to insert probes to use as an input terminal of the Multimeter.
HOW TO OPERATE:
At first, you need to know what type of electrical quantity you want to measure with your Multimeter. (A typical Multimeter can measure AC Voltage, DC Voltage, Current, Resistance, and continuity.)
1.1. Measuring Voltage (DC)::
As we know there will be no flow of current in a circuit if there is no potential difference, as per Ohm’s law (I∝V). This potential difference is measured in unit Volt.
An Important note, we cannot measure an unlimited amount of voltage with a Multimeter. A typical Multimeter has a limitation of maximum and minimum voltage (voltage range), between which we can measure. The Multimeter in the image below has a range from o to 600 volts. Now let’s look at the knob,
There are six ranges of value to measure. 0 to 200mV, 200mV to 2V, 2V to 20V, 20V to 200V, 200V to 600V. So, the maximum reading that the multimeter can take is 600V. After that, the internal circuitry is very likely to get fried.
Now we need to have an idea about the approximate value of the voltage that we are going to measure beforehand we start measuring the value. If it is a high voltage source (mainly converted from high voltage AC) we need to use the uppermost interval i.e. 200V to 600V. As the source tends to lower value, we should choose lower intervals like 20V to 200V or 2V to 20V etc. These intervals are selected by just rotating and fixing the selector to a marked interval. This is the adjustment we need to do on the Multimeter, but this alone won’t give us any value on the screen. Now we need to put the RED wire into the port marked as VΩmA and the BLACK wire to COM port. Which will be used as +Ve and GND input terminals respectively. Now just touch the sharp metallic end of RED (+Ve) probe to the source’s positive terminal and Black one (Gnd) to the negative terminal (GND), the Multimeter will show the value of the potential difference in Volt unit on the display.
Say, we want to measure the potential difference between 2 terminals of a common 6F22 type 9V battery. So, now we need to find out appropriate interval where we should fix the selector. 9V is less than 20V and greater than 2V. So, 2V-20V is the correct interval and we should set our selector to “20” marking.
NOTE: THE MARKINGS ON MULTIMETER REPRESENTS UPPER LIMIT. SO, "20" MEANS 2V - 20V RANGE. WE MUST NOT SELECT THE LOWER INTERVAL THAN THE VALUE WE ARE MEASURING, TO SAVE THE MULTIMETER FROM UNINTENTIONAL DESTRUCTION.
1.2. Measuring Voltage (AC)::
OK, now it’s time to measure some AC voltage. You are already aware how to measure DC voltage. So, almost nothing new here. All rules are same but only selector position is changed. From the previous image, you can see that the multimeter can measure maximum of 600V AC. There are two intervals for this case, 0 to 200V and 200V to 600V. As AC is much harmful than DC, it is recommended to fix the selector at 600V marking (200V – 600V range) initially and only then switch to lower ranges if reading in 600v position is smaller than 200V.
the selector is fixed to 600 marking on above picture. When you are not sure which value you are going to measure, opt for the maximum range available.
2. Measuring Current::
To measure current we have to use the same principle with the probes as we have already described previously. But we have to be careful with it. A typical Multimeter is not much efficient with measurement of current on an open-circuit (i.e. it can damage the MM if you connect the probes to a 10A current source for a long time). We just need to connect our probes to a circuit wire in series, which is shown in below diagram.
According to the previous image of selector knob, this multimeter can measure up to 10A current. The intervals are 0 to 200µA, 200µA to 2mA, 2mA to 20mA, 20mA to 200mA, 200mA to 10A.
For measuring current below 200mA, we should connect red probe to VΩmA and black one to GND, as we have done while measuring DC and AC voltage. The probe connection is like below,
If we want to measure more than 200mA (maximum 10A) current on a circuit, we need to change the RED wire to the 10A port and measure the value.
As 10A is a huge amount of current, we must NOT connect the probe for more than 10 seconds. this is how we measure current with a Multi Meter.
NOTE: IF RED PROBE CONNECTION IS NOT CHANGED ACCORDINGLY WHILE MEASURING ABOVE 200mA i.e. RED PROBE STILL CONNECTED TO VΩmA PORT, THE MULTIMETER WILL BE DAMAGED.
To measure the resistance of a wire or a resistor you just have to put your Multi Meter knob to Resistance intervals on your MM. It is normally denoted by Ω sign in a multimeter. Typical Multi Meter can measure up to few Mega Ohms of resistance. In the image of selector button of previous images, you can see that this multi meter can measure 5 intervals. 0 to 200Ω, 200Ω to 2KΩ, 2KΩ to 20KΩ, 20KΩ to 200KΩ, 200KΩ to 2MΩ. To measure a resistor’s resistance you need to fix the selector knob to correct position just same as previous cases. If you get a One (1) on leftmost corner of display, it means either you have chosen lower interval than the original value of resistor (e.g. resistor’s value is 47KΩ but you chose 20K marking which represents 2K-20K interval, smaller than your resistor value), or the connection between resistor’s legs and probes is not established properly. Double check both criteria. The display looks like below when the said two criteria happen,
The below diagram represents how to measure resistance by touching probes.
But you can easily understand the value of a resistor by simply looking at it. How? OK, here comes the term “resistor color code”. On resistors, you can see 3-4 bands of colors like the above picture. Each color represents a specific value. You can easily learn how to read color codes from this nice tutorial. This wikiHow post will give you some cool tricks about how to memorize the color code forever. So, you should look at this color code chart every time you want to know a resistor.
But, what to do if color code is missing (somehow erased, blurred or not present at all)?. Now lets put our Multi Meter to use, just fix the selector at lowermost (minimum interval i.e. 0-200Ω) position and increase the interval values by rotating the knob until you get some integer value reading on display except a One (1) at leftmost corner of display. As it is already said, when resistor is higher in value than the selected interval permits, reading on-screen is 1 at leftmost position. So it is wise to start from minimum and move toward maximum.
Example, start with 0-200Ω interval, if after touching the probes to resistor display shows 1 at leftmost corner, then we have to increase the interval to next level i.e., 200Ω-2KΩ. Again touch the probes properly. If we end up with 01 at leftmost corner of display again, we have to increase the interval again to 2kΩ -20KΩ, Now it gives some real value, then OK and stop right there. Or continue the same process.
So, if gives 1 as Output on the display it means we have to increase our interval on the MM knob; and for 0 on the display we have to decrease the interval. This is how you Measure resistance with a Multi Meter.
NOTE: TO GET CORRECT RESULT FOLLOW THE STATED RULES: 1. ALWAYS PUT THE RESISTOR ON NON-CONDUCTING SURFACE. SO, NEVER PLACE IT ON METALLIC SURFACE RATHER USE WOODEN OR SIMILAR SURFACE. 2. TRY NOT TO TOUCH THE PROBES AND RESISTOR LEGS WITH BARE HAND. IF BODY CONTACT IS AVOIDED, YOU'LL GET BEST READING. 3. NEVER MEASURE RESISTANCE IN A CIRCUIT THAT IS CONNECTED TO POWER SOURCE. DISCONNECT POWER SUPPLY FIRST, THEN MEASURE RESISTANCE. ELSE MULTI METER MAY GET DAMAGED.
4. Continuity Test::
At first we need to know what continuity is assuming most of you are beginners. Continuity is a property of electronic/electrical circuit, which means there is no gap or break (open link) in the circuit. All necessary electric components are connected to each other so that it can perform its job flawlessly.
Assume you are holding a piece of wire between two hands. Now, the wire is one piece and so continuous. But now your friend comes and make a cut in the middle of the wire. You are still holding two ends, but is it continuous any more? NO. Because your stupid friend did some nuisance. So, This is the way we can describe “Continuity”. Actually, when you make circuits, some unintentional loose connection may remain there and that voids continuity of circuit. We need to find out them using the Continuity Test feature of our Multi meter.
To check continuity with multi meter you need to adjust the selector knob according to the position shown in the picture.
Now touch two probes of the Multi meter to the end of a path which you want to check continuous or not. If the multi meter gives a continuous shrill sound from the buzzer then the circuit’s continuity is just fine. If it gives no sound then the path is broken somewhere or not connected. Or, may be you have not touched the probes correctly. Figures given below shows how it works;
NOTE: NEVER TEST CONTINUITY IN A CIRCUIT THAT IS CONNECTED TO POWER SOURCE. IT WILL RESULT A DAMAGED MULTI METER. SO ALWAYS TURN THE POWER OFF BEFORE YOU TAKE THE TEST.
So, now you have learned basic operations of a typical multi meter. But a typical multi meter can do some more tasks for you, e.g Diode checking, Transistor checking. But those functions are not as basic as the above functions. You must have some good knowledge in electronics and solid-state to use those features.
I’ll add those things very soon in this post, don’t worry. But till then stay tuned and learn these basic operations of a multi meter.
And if you are really enthusiastic hobbyist of electronics, then you may find it interesting to set up your very own electronics lab with ease. SO, GO AHEAD AND CHECK OUT BEGINNER? SET UP YOUR FIRST LAB .
- Author: DIZ (Dipanjan)
- Editor: Rik