How to use a multimeter – Most resourceful guidelines on the web
As an electrician, using a multimeter should be at your fingertips. If anything, you should be able to measure both current and voltage which are the basic electrical units that a multimeter does measure. Despite current and voltage, there is plenty more than a multimeter can measure.
A multimeter is an indispensable tool that you can use when diagnosing circuits or your alkaline batteries as well as those in your vehicle.
Well, to cut to the chase, let’s have a look at how to use a multimeter regarding the common electrical units we may have to measure daily.
Parts of a digital multimeter.
First off, let’s take a look at the construction of a digital multimeter, shall we?
The selection knob.
Being probably the most important part of a multimeter, this is what you use to switch to the different units you want to measure. You’ll be using this to power off the device, measuring continuity, voltage and resistance (both AC and DC depending on the type of multimeter) among other units.
The selection knob can also be used to select the correct range of measurement if you are using a manual ranging meter.
The display is just as it is. It’s simply what will allow you to get the readings of what you are measuring. These come in different types; they can either be backlit or not and they also come with different counts.
Most multimeters come with three ports and this is where the banana ends of the probes go. The COM port is for the earth wire while the other ones are for the live one.
On a standard meter, one port is labeled mAVΩ and you should use it for current less than 200mA while the one labeled 10A is for anything greater than 200mA.
Common units of measurement using a multimeter.
Moving on to the main agenda, here’s how to use a multimeter whether you need one for industrial use, home use or automotive troubleshooting.
To do this, first turn off the power of the circuit being measured. Current measurement requires you to connect the multimeter in series with the circuit. It is also important that you observe the amperage; i.e. have the live probe connected to the correct port either the 20A, 10A, or the mAVΩ.
If the multimeter is autoranging, set the dial to the mA or the A setting then turn the power on. If the range is too high, you can switch to a lower range to get a more accurate reading.
One safety measure to observe after measuring current is turning the dial to the V position since the meter is a short circuit when the dial is in the amperage position. If you happen to connect the meter to a voltage source, you may blow up a fuse or even worse the whole meter.
In order to do this, first of all, power off the circuit under measurement. You should then ensure the ground (black probe) is in the COM port and the red one in the port marked V or Ω or possibly the diode symbol.
If it’s manual ranging, pick a range that’ll give the needed accuracy. If you think your load is maybe 12V, pick 20V with the dial for more decimal places which would not be the case for turning the dial to 200V.
The multimeter should also be connected in parallel. Connect the black probe to the first point, power up your circuit then touch the red probe to the other end.
First off, turn off all the power as you did in voltage and current measurement. Disconnect one end of the resistance from the circuit which may involve desoldering the components since there may be other resistors in the circuit.
Connect the probes to the resistor in parallel and turn the dial to the lowest ohm range which in most cases is the 200-ohm range. Since resistance measurement can be measured with the probes being in any end of the component, touch the probe tips on each end.
If the reading is “I”, then the resistance is greater than that which can be displayed on the selected range setting hence you should switch to a higher range till a range is displayed on the screen.
Checking for fuses and continuity.
How to use a multimeter when checking for continuity is probably the simplest way via which you can use a multimeter.
In order to do this, turn the dial to the continuity range which is indicated by a series of circle arcs. You should connect the probes in parallel as you did in voltage measurement.
If you have any device on the circuit that needs to undergo the continuity check, ensure it is powered down. Have the probe on either end of the conductor or fuse that needs checking. For a resistance that’s less than 30 ohms, you’ll hear a beep and if there is a break in continuity, the “1” will be displayed on the meter.
Checking for diodes.
Though this is not one of the major uses of a multimeter, diode check can be quite convenient. By using a multimeter, you can be able to check whether a diode is short or open circuited.
Here’s how to go about it:
You should first turn the dial to the diode testing mode that is indicated by a triangle with a vertical bar on one end. Ensure that the probes on the meter are connected in parallel.
Have the tip of the negative probe touching one end of the diode and that of the positive one on the other end. The black probe should be on the cathode side of the diode which is also the side of the bar and the red one on the opposite end.
With the probes connected this way, the diode should be able to conduct hence indicating a voltage reading on the meter. A silicon diode should read about 0.6 volts whereas a Schottky one should read 0.2. reversing the diodes should indicate a 1 since it is open circuited and won’t be conducting any electricity.
In any case, if the meter reading is one, the diode is likely to be faulty and if the reading is a value that is close to zero, then you are most likely working with a short-circuited diode.
Watch The definitive guide How to use a multimeter the Best Way
Additional features on a multimeter.
Other than just using the dial when it comes to setting your values on a multimeter, some multimeters do come with extra features.
The data hold feature.
In some cases, you may need to unplug the probes for one reason or the other and at the same time would also like to take your readings from the display. What the data hold feature does is freeze the current value on your display even after you remove the test leads from the component you are troubleshooting.
The min/max button
Besides the data hold function, there is also the min/max button. The min/max button able to capture the maximum or minimum value of a signal that is measured over a period of time. the multimeter will then be able to hold the maximum or minimum values temporarily.
As you take your measurements and register a new max/min value, you should first of all press the shift key which is normally the yellow button. This can be on the extreme left or extreme right depending on the type of multimeter you are using.
Upon doing so, the present max/min value will be displayed on the screen which indicates that the max/min recording process has begun.
How to use a multimeter- safety precautions.
Regardless of how much experience you have when it comes to using a multimeter, you should pay heed to the safety precautions just like any other electrician.
Here are some of the things you should always have in mind…
How to use a multimeter - infographics source : toolnerds.com