The digital multimeter is one of the most important tools in the electronics professional’s and electronics hobbyist’s toolbox, so much so in fact that the electronics aficionado usually has more than one. However, digital multimeters are used not only by electronics enthusiasts but also by other professionals such as car mechanics and electricians, who often have slightly different needs with respect to multimeter specifications. As a consequence, the humble digital multimeter comes in a variety of different flavours which cater to the needs of different professions. Therefore the electronics hobbyist needs to know beforehand what specifications are appropriate for electronics work, and what he or she should be looking for when buying a digital multimeter. So what's the best multimeter for electronics work and what should a newly-minted electronics hobbyist be looking for in their new digital multimeter? Let's try to answer those questions.
Probably one of the best ways to choose a digital multimeter for electronics work is to follow the advice of electronics experts who have spent years working around electronics and with multimeters of many kinds. Today, one of the best electronics gurus out there is Dave Jones from EEVblog. Fortunately, he has provided us with his expert opinion on this very subject in an excellent video detailing practically all the characteristics to look out for when trying to choose the best multimeter for an electronics hobbyist:
As you can see from the (somewhat lengthy!) video there are a large number of characteristics to watch out for when purchasing a digital multimeter for electronics, making it hard to keep track of them all when going through potential multimeter candidates. So to make it a little easier on us, below you will find a summary of the essential points raised by Dave, that electronics hobbyists and even electronics professionals should find useful.
Ideally the electronics hobbyist, and certainly the electronics professional, should get a ‘brand-name’ digital multimeter (DMM). This is because established DMM companies have a reputation to uphold and so produce good quality meters. Unfortunately however, better quality is usually synonymous with 'more expensive' but for electronics professionals and serious amateurs alike, getting a good quality meter is a must. Some of the more established digital multimeter brands are listed below (however, the list is not exhaustive):
Auto-ranging or manual-ranging
- The digital multimeter should be able to measure both AC voltage and DC voltage.
- For both AC and DC voltage, the digital multimeter should be capable of measuring millivolts (eg. 200mV) up to approximately 1000V.
- For electronics work, the digital multimeter should be capable of measuring from about 200Ω up to a minimum of 20MΩ, and higher if possible.
- For both AC and DC ranges: the digital multimeter should be able to measure in both the microAmp (µA) range as well as in the milliAmp (mA) and Amp (A) ranges.
- The amperage measurement upper limit of the digital multimeter should be at least 10-20A.
- Less expensive multimeters will often have a combined ‘VΩmA’ terminal (image below left) - this is not recommended. For safety reasons, it is preferred that the current (µA / mA / A) terminals are separate from voltage and resistance (VΩ) terminal (image below right).
The digital multimeter should have at least 10MΩ input impedance to prevent it from significantly changing the voltage measured across high resistance components.
Diode measuring function
- 1Slow latching time: this leads to a slight delay in the beep when a continuous circuit is detected. In general, one should avoid this type of digital multimeter as it is not only annoying but can also prevent you from doing certain useful measuring techniques such as quickly swiping across the individual legs of an integrated circuit while checking continuity.
- 2Fast latching time: this means that a beep is sounded almost instantaneously upon touching of the probes to a continuous circuit. This is the type of continuity function that one wants in their digital multimeters.
Battery and fuse access
Better digital multimeters will provide easy access (usually a bespoke door) to the battery that powers it, as well as the fuses that protect it.
Long battery life
Capacitance measuring function
Relative measurement feature
This feature is found on some digital multimeters and is useful in that it allows the meter to compensate for the internal resistance of the probes themselves (and their wires) which might skew readings slightly. It can also be used to measure a change in the voltage from a reference value.
This allows the operator to set the digital multimeter so that it records the minimum and maximum values that are observed during a measurement.
This feature freezes the readings on the meter so that the user does not have to constantly see the display screen, and holds the reading even after the probes are removed. There are 2 types of Hold function that are available on today’s consumer digital multimeters:
1. Auto-hold which is found in the higher-end digital multimeters, and automatically freezes the reading when the measurement has been made usually at the same time as sounding a beep. This is the (much) preferred option!
2. Manual-hold which is found on less expensive multimeters, which requires the operator to push a manual hold button to freeze the reading when taking a measurement. This is often difficult to operate since the operator’s hands are usually occupied with holding the probes during a measurement, making it hard to press the hold button!
This feature is often found on digital multimeters and usually comes with a separate thermocouple probe.
Clear display with big digits
This can make taking readings much easier and the display can also be seen from far if necessary.
This allows for use of the digital multimeter in low-light conditions.
When it comes to counts, the more counts there are on a digital multimeter, the better the meter, however this should not come at the expense of accuracy which can be checked using the basic formula below. In general, one can expect that a good multimeter will have at least 4000 counts (which according the the table below should have at least a DC voltage accuracy of ±0.25%).
True RMS and AC bandwidth
Display updating speed
This refers to how often the display is updated when performing a measurement. Obviously the faster the updating, the more closely it will represent the parameter being measured especially if it is changing rapidly. In general:
- Higher-end digital multimeter displays will update around 4 times a second.
- Less expensive consumer digital multimeters will update the display about 2 times a second.
- For comparison, top-notch professional (and expensive!) Agilent digital multimeters will update the display 8 - 15 times a second.
Digital multimeters with a low-pass filter can be useful when working on motor drives and other noisy circuits as they will filter out a lot of the high frequency noise that is generated within such circuits. However, for a regular everyday-use meter, this feature is not essential.
The digital multimeter should be relatively robust with features like a rubberised jacket that protect it from rough handling.
If you plan on doing lots of current measurements with your digital multimeter, then the burden voltage of the meter (or the voltage drop when you place a meter in series with the circuit for current measurement) should not be more than 1mV per mA.
Non-essential features of digital multimeters for electronics work
Transistor hFE tester
This is a gimmicky feature and often goes unused by electronics professionals and enthusiasts. To drive the point home, high-end digital multimeters will never have a dedicated ‘Transistor hFE tester’.
Frequency & Duty cycle
Another feature that is rarely used on a digital multimeter is making frequency and duty cycle measurements. This is because oscilloscopes are better suited to performing these functions. However, if the frequency feature is present on a digital multimeter, then the higher the frequency range, the better, with the hundreds of KiloHertz (KHz) into the several MegaHertz (MHz) ranges being the most likely to be useful.
Data-logging and Graphing digital multimeters
These are generally more expensive than the regular digital multimeters and the quality of other important features on them are often sacrificed to keep their prices reasonable. In addition, these types of multimeters tend to use a lot of battery power so do not represent a good everyday-use multimeter.