The Humble MULTIMETER. What can one measure with it.

Hey everyone.

Despite being very tied up in high level digital development and various other projects I decided to do a small article about multimeters and what one can typically measure with one. I will also cover basic component testing etc in this post.

Multimeters go back many years. The volt meter and amp meter or ammeter predate all the fancy test gear we have available now days however as an engineering type I make use of one of my multimeters almost every day.

Below you can see my multimeters layed out: Please note that these pics are taken on cell phone so not best quality.

These are the four meters that I make use of the most.

If I am wanting to do data logging or analysis I generally go to my Uni-T UT71A as it has the capability of connecting to PC via USB which allows me to log voltages, currents or just about anything without being around.

Below is the UT71A closeup.

   

This meter also has a fantastic large LCD display and allows you to check voltages etc with very fine levels.

My spare meter is my little Major Tech MT24 which has seen me through many jobs, repairs and designs and is used fairly often when a small meter is needed on the bench to measure secondary signals.

   

I find this meter to be very accurate and great value for money.

My third meter and my primary bench meter (my go to meter) is my Major Tech MT1880 IV. This meter was a lucky find at a local second hand store and after a good cleanup she sits proud on my bench as my primary meter. Why this meter some may ask. Well its simple, clean and does most of what I need on a single unit. I also enjoy the analogue (digital) bar at the bottom.

   

The last meter and my least capable but still very capable meter is the TA EM5511. All the other meters here where well over R1000 each whilst this unit set me back about R200.00 second hand.

I will use this meter for my tutorial and article.

   

The first few things you will notice is that all my meters are Auto Ranging, they all have backlights and are all very multitask meters. The Auto Ranging feature used to be reserved for the high end meters however some of the newer low end meters also have this feature now days and it really does make sense to get one which is auto ranging as it does two positive things for you. The first is that you do not have to keep selecting ranges all the time so is convenient and the second is that your rotary button will not wear out as quickly as it will be used less.

I have pretty much gotten rid of my Fluke 77 and various other meters as I really was not using them half as much as these and these cover everything that I would want to cover in my work and experimenting.

Anyway this is not technically a review of multimeters, That will be done pretty soon as well as reviews of development boards, Oscilloscopes etc. All in due coarse. This is more a tutorial on multimeters and how to use them and what you can measure.

For this article I will be using the above TA multimeter as it is simple, clean and most probably closer to what many people starting out will be using. If you know what you are doing you wont be here after all.

So lets start.

On all meters you have what I call the mode selector which is usually a rotary dial with a whole bunch of options. If you have a autoranging meter then the options will be less.

Below a close up":

From left to right going clockwise you will see the modes as below:

1. OFF (Power Off Mode)
2. V~ (Voltage AC – Alternating Current) which is the kind of stuff that comes out of our wall sockets and out of step down transformers etc.
3. V= (Voltage DC – Direct Current) this is what comes out of batteries and power supplies that output DC power. This is what you will most likely measure a lot as this is cells, batteries, power supplies and so many other things.
4. OHMS (This is to measure resistance or ohms) Used to measure circuit resistance, component resistance and so many other things.
5. Diode / Continuity Test (In diode test mode you are able to measure the voltage drop of a PN junction such as a diode, transistor and various other devices. In the continuity mode it will beep if the resistance is below a certain value of around 30ohms.
6. Capacitor Test (This is limited on most meters but does come in handy for checking capacitor values and testing capacitors.
7. Hz% ( This is used for measuring frequency and duty cycle) For example if you wanted to use a microcontroller such as an Arduino to control the speed of a motor or brightness of a LED then you could use Pulse Width Modulation or PWM. In the case of Arduino this is usually defaulted to 490hz. You are then able to measure this frequency as well as its duty cycle. The duty cycle of PWM is used to control the amount or speed of the device or motor. For example at 0% duty cycle the switching mosfet or transistor would be off whilst at 100% it will be at full power or speed. This is the most popular method for using microcontrollers to control large motors or lights etc. More on PWM and how to use it in another article.
8. Deg C (Measuring temperatures of various devices)
9. mG (In the case of this meter it is used to measure the EMF from the sensor on the top of the meter.)
10. uA ( Measuring very small currents or Micro Amps)
11. mA ( Measuring Milliamps)
12. A ( Measuring Amps)

So basically with this little meter you can fault diagnose most electronic or electrical components, you can tinker with digital signals and various other things.

I am not going to cover the entire how to use a multimeter as this is more about showing you what can be accomplished using a humble multimeter.

As a field components level technician for many years working for one of South Africa’s biggest RF or radio frequency networks I learnt how to use a multimeter for more than it was originally planned and even went so far as to build my own probe devices for measuring RF signals and others.

I will upload a video to this post in due coarse showing you how to use this meter to measure various signals.

Go out and grab a multimeter. It will make your day, unless you already have one. ;-)

 

Cheers for now

Dionne