No matter what industry you are in, you will have tools and equipment that you use on a daily basis.
A chef and his knife, a carpenter and his hammer, an artist and his paintbrush.
With time these tools will degrade and require you to either buy new ones or have them serviced.
Having a tool that is in optimal condition is crucial between performing the task poorly or properly.
So when it comes to whether you need to calibrate a multimeter, the simple answer is yes. A multimeter is an electronic measuring instrument which just like any other electronic equipment, will need servicing with time to maintain its accuracy.
If you are unsure of why you need to calibrate your multimeter, or the benefits of calibration, this article will provide you with the basics to get you own your way to multimeter accuracy.
What is calibration?
Calibration is a term synonymous with measurement technology.
It is the comparison of the measurement values of a piece of measurement equipment compared to the values of the calibration standard of known accuracy.
The final result of the calibration test can either be; there is no significant error (the device being tested is showing accurate readings), there is a slight error (but not big enough for and adjustments to be made) and there is a significant error and proper adjustments need to be made to ensure device is operating within the calibration standard.
If you want to put it simply, calibration can be seen as a comparison test.
What causes multimeters to lose accuracy?
All multimeters come with a manual with specifications of how to store your multimeter, and what are the best conditions.
Because the multimeter contains electronic components, things like temperature, humidity will have a direct impact on its accuracy.
Other variables that impact the performance of a multimeter can be line voltage. They have a specific range and reading outside this range will add to the errors.
One thing to take into account if readings do not seem right, is the batteries that the multimeter is running on.
If the batteries are running low it can affect the readings.
Why is calibration important?
As you probably already know, time can work for, or against you. When it comes to measuring devices, their accuracy will degrade over time.
As I mentioned above there many external conditions that can impact the accuracy of measuring device like a multimeter.
But, sooner or later no matter how well you store it, the accuracy will drop.
But why is it so important to calibrate your multimeter?
Quite simply, it is important because it is going to directly influence the readings you take such as voltage, current, resistance etc.
Say you are doing some fault finding in a circuit and need to calculate the voltage at a certain point. The key element to finding the right voltage all depends on the accuracy of your multimeter. If it is off quite considerably it will not benefit you.
Designing a simple voltage divider circuit will not be possible if your multimeter is not reading the right resistance due to it not being calibrated.
What needs to be calibrated?
The multimeter is a very useful measurement equipment. It has a lot of features and many measuring capabilities.
The most common of them are voltage, current and resistance.
Other aspects that a multimeter can measure (depending on its complexity) include, continuity, capacitance, frequency, diode test, AC voltage and current.
So, when it comes to calibrating a multimeter, there is not one but many calibration tests that need to be performed.
Calibrating just one part of it and not the others will hinder the overall performance as all these measuring capabilities of a multimeter work together. If there is a weak-link the whole system is flawed.
Other causes of wrong readings?
There will be other instances where your multimeter will be giving you wrong readings.
You might read a voltage value even though no voltage is being applied. Or, when you do try to measure voltage you get a zero readings.
Your first assumption might be that you need to calibrate your device. However, this is not the issue.
This problem will be that you have blown the internal fuse. Multimeters have specified ranges of voltage and amps that you can measure.
Attempting to read outside of this range will blow the internal fuse. You will then have to replace the fuse to get back to normal working conditions.
So, if you have wrong readings, this does not necessarily mean you have to calibrate your multimeter, it could just be the simple task of replacing a fuse.
Analog vs Digital Multimeters
There are two types of multimeters available; Analog and Digital.
The main most notable difference between the two is their display. The Analog multimeter displays its readings in the form of a needle. Whereas the digital multimeter displays its measurements as numbers on a screen.
There are other differences internally in the circuitry with how each of them does its measurements.
The advantage that an analog multimeter has over its digital counterpart is that when checking a diode, the analog multimeter is more accurate. Other than that most people opt to use a digital multimeter.
Coming back to our main point of calibration. No matter what kind of multimeter you have (analog or digital) it will still require you to calibrate it with time.
The difference in calibration between the two is that an analog multimeter is calibrated manually while the digital one is done automatically.
How often do I need to calibrate a multimeter?
The frequency at which you calibrate your multimeter all depends on factors such as manufacturers specification, and application its being used.
As we all know, every electronic device that you buy whether a consumer product or measurement device, comes with a manual that includes the best practices specified by the manufacturer.
Things like how to use it, dos and don’ts, warnings etc. With multimeters the manufacturer will have specifications on how often the device will need to be calibrated. Obviously you do not have to follow this exactly, but to get the best out of your multimeter it is advisable.
Things to consider as well, is whether the multimeter is analog or digital.
If you do not receive a manual, or your manual does not include information on calibration, you can always contact the manufacturer or check their website.
The next factor to consider is the application in which the multimeter is being used. Most notably the demands for accuracy.
Say the multimeter is being used to test medical equipment, it is paramount that the measuring equipment is of the highest accuracy. So, in this instance it would be mandatory to calibrate at a higher frequency.
If you are a hobbyist, accuracy is not your greatest concern (unless you are developing medical equipment of course). So the frequency at which you calibrate your multimeter would be much longer.
As you can see there are a couple of considerations to take into account on how often you need to calibrate your multimeter.
Do I need a professional to calibrate my multimeter?
If you use a multimeter for your own personal use, I would not suggest getting a professional to calibrate it, due to the fact that it can be quite expensive.
If, however, you cannot be bothered to do it yourself or want your multimeter to be operating at peak performance then I would suggest getting a professional to calibrate it.
Going back to the testing of medical equipment, as I mentioned accuracy is of great importance. So, calibrating measurement equipment would require a professional.
Another important thing to mention is paperwork. For legal purposes companies get professionals to calibrate their measurement equipment not only to maintain their devices, but to keep a trail of legal/safety paperwork. This way they can keep a track of when they are serviced for legal and safety reasons.
So, if accuracy and legality aren’t of your greatest concerns I would not use a professional to calibrate a multimeter.
Where can I get my multimeter calibrated?
Say you do choose to calibrate your multimeter using a professional, where would be the best places?
Depending on which part of the world you live in, a quick google search of “multimeter calibration” will give you a list of many companies that can help you in your quest to calibration.
Or, you could contact the manufacturer of your multimeter and check if they include services which provide calibrating your device.
The cost of calibration again depends on the company and where you are located. I live in New Zealand and the price ranges from $95 – $270 NZD depending on the type of multimeter.
How to calibrate a multimeter
If you do decide to calibrate your multimeter yourself, below are great resources on how to do it.
Digital Multimeter:
Analog Multimeter:
https://www.doityourself.com/stry/how-to-calibrate-an-analog-voltmeter
Conclusion
So, hopefully you now see when it comes to whether you need to calibrate your multimeter the importance of doing so.
No matter what application it is being used in, calibration helps keep your device working as it should be from the day you bought it.
Depending on accuracy, you may need to get a professional to do it for you, but if you are a hobbyist and are not fussed with the finer details, doing it yourself is totally fine.
As mentioned earlier, things like temperature and humidity degrade electronic equipment faster over time. So, store your multimeter in cooler conditions. Consult your multimeters manufacturers manual or website for further details.
