How to Buy a Multimeter

Are you planning to buy a multimeter and need help? Here are some timps

How to Buy a Multimeter covers what you need to know to select a meter for DIY electronics. It focuses on the needs for audio electronics, but it’s purposely kept general in nature.

Handheld Digital Multimeters are mainly used to measure resistance, as well as DC/AC voltage and current. Common multimeters can be divided into two types, desktop and handheld digital multimeters depending on their sizes. A handheld digital multimeter is basically composed of Analogue Front End (AFE), MCU, Human-machine interface and Power supply. The design of handheld multimeters should focus on the features of low power, high performance and compact size.

Look for these features when buying a multimeter article tells that multimeters can be handy for troubleshooting PC power problems (I would say it is a must have). But the range of features and prices can be confusing when you’re shopping for one. Before you waste time and money, find out which features are essential and which are merely nice to have.

EEVblog #75 – Digital Multimeter Buying Guide for Beginners

EEVblog #91 – $50 Multimeter Shootout – Extech EX330, Amprobe AM220, Elenco, Vichy VC99, GS Pro-50

$50 Multimeter Comparison and Teardown article tells about a very nice video series on multimeters. Here is maybe the most interesting video from it:

$50 Multimeter Shootout – Part 7 – 15 DMMs Compared! – Teardowns – #0074

 

12 Comments

  1. Washington Plumber says:

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    Reply
  2. Tomi Engdahl says:

    Why You Shouldn’t Quite Forget The Moving Coil Multimeter
    https://hackaday.com/2017/11/08/why-you-shouldnt-quite-forget-the-moving-coil-multimeter/

    There was a period through the 1980s into the 1990s, when the transition between moving coil and digital was in full swing. Everyone wanted a digital meter because they were cool. They had both precision and accuracy, instead of saying “That’s about 5 volts”, you now knew it was exactly 4.98 volts.

    So we can make fun of 1980s fashions, both sartorially and in test equipment, but what’s the real benefit of a digital meter? It lies in the internal resistance. When you hook a moving-coil meter into a circuit, you are doing work, drawing energy from the circuit being measured to move that pointer. Imagine the meter itself in a hypothetical inexpensive moving-coil multimeter, that has a full scale deflection of about half a milliamp. To take a reading at full scale the meter must then draw 0.5 mA from the circuit being measured. So to give a full scale deflection of 10 V for example the meter must have a resistor in series with it of value 10 KΩ, and measuring a voltage thus involves placing what is in effect a 10 KΩ resistor into the circuit in question. Most decent moving coil multimeters had meters with much lower full scale deflections that required greater series resistances, but the principle was the same. A moving coil multimeter loads the circuit it was testing, altering its characteristics.

    The problem of meter resistance was one for which there were solutions in the age before digital meters. Many decades ago you could buy a valve (tube) voltmeter

    So why should you have a moving-coil meter on your bench, if digital meters are so good? Aside from looking a bit retro and never having to worry about the batteries running out, that is. The answer lies in being able to measure voltages that change. If you have ever worked with radio or with analogue circuits that require adjustment you will know something of this, tuning for a peak or a trough is extremely difficult when you have no view of the trend. A typical use for a moving coil meter here is to set up an RF amplifier by tuning a tank coil, there will always be a peak in the current drawn by the amplifier as the coil reaches resonance.

    The moving coil meter of choice here for the last 30 years or so has been a venerable Avo 8. This is the classic mid-twentieth-century multimeter, a large and heavy Bakelite unit with an extremely high quality meter lurking within it.

    MF47 can be had from the usual Chinese suppliers for about £15, or $20. It’s not the most compact of multimeters, having a front panel slightly larger than and being about three times as thick as a DVD case.

    Comments:

    A vintage needle meter – hipster engineer.

    Brain-fart, but we use to have both. The analog was pretty cheap, even back in the day.

    There’s things that you should probably check out with other types of equipment that you can at least “see happening” on a moving coil meter, that are very hard to read on a digital. Examples might be voltage ripple (needle twitching), back EMF of a coil, the difference between a capacitor that’s failed open circuit and one that’s still capacitating away (Whether the value has drifted or not.)

    Reply
  3. Tomi Engdahl says:

    The Worst Piece Of Test Equipment You’ve Got To Try Hacking
    https://hackaday.com/2017/11/28/the-worst-piece-of-test-equipment-youve-got-to-try-hacking/

    I have a fascination with the various online vendors of electronics and other manufactured goods from China. Here are listed the latest wonders from Shenzhen or wherever, which you can have for a surprisingly reasonable price, with the mild inconvenience of a three week wait for the postage.

    So when I was shopping for a multimeter recently I took a quick look to see what the cheapest model from that particular supplier was. For somewhere around £2.50 or just over $3, I could have a little pocket analogue multimeter, the kind of “My first multimeter” that one might have found in the 1980s. They weren’t too bad, I thought, and ordered one for less than a pint of beer in a British pub.

    What arrived was promising enough, in a plastic blister pack, the Sunma YX1000A.

    Opening up the meter for a teardown, and I found a single printed circuit board, with as expected the selector switch formed by PCB pads. With the exception of a through-hole rectifier diode and trimmer used as the zero adjustment for the resistance ranges, all components were surface-mount.

    There was no plating on the pads, save for the HASL or similar PCB tinning. Those pocket meters back in the day would usually fail because of oxidation of these contacts, no doubt this one would eventually succumb to the same fate.

    The Sunma YX100A then: A case with a chip in it, a wildly oscillating meter mechanism that evidently has no damping, a stripe of grey paint for a parallax mirror, and a consistent 20% low reading. Even with a slightly tongue in cheek review, it’s fair to say that I have had better multimeters than the Sunma. In fact it’s fair to say that every multimeter I have ever used has been better than the Sunma. It’s possible that to make a multimeter worse than the Sunma would be extremely difficult, but they must have done it, because as they say, this is the “Improved Modeli”. Just how bad was the previous unimproved model?

    Reply
  4. Tomi Engdahl says:

    10 Things You Must Know About Benchtop Digital Multimeters
    https://www.electronicdesign.com/test-measurement/10-things-you-must-know-about-benchtop-digital-multimeters

    So, you thought you knew everything about benchtop digital multimeters. Here are 10 things you may not be aware of, but are important factors in getting the most from your DMM.

    Design engineers use digital multimeters (DMMs) almost every day. They’re the most commonly used instruments on any design engineer’s bench. A DMM could be utilized to make quick and simple voltage measurement or data log temperature measurements over time. Whatever the use, it must work.

    The DMM is the workhorse of the engineering bench. In exchange for all of the work done by our DMM, we expect to do very little upkeep and maintenance in return.

    1. Bench vs. Handheld

    Though this article will primarily focus on benchtop DMMs and not handheld DMMs, do keep in mind that many of the topics and concepts apply to both platforms. In most cases, a typical benchtop DMM will have higher accuracy, better resolution, more sophisticated system programmability, and more advanced functionalities compared to a handheld DMM.

    Connectivity is a big distinguishing factor between benchtop and handheld DMMs. Some handheld DMMs provide very simple USB or Bluetooth connectivity and mobile application. Benchtop DMMs typically offer more options in wired connectivity, such as LAN, USB, or GPIB, as well as software drivers. This allows for a sophisticated level of automated testing and software control.

    2. Digits, Accuracy, Resolution

    Different brands specify accuracy differently, though, so it can get complicated. The bottom line is that it ultimately translates into a range of possible returned measured values. Accuracy and resolution together give the user a big picture of the quality of measurements one can expect from a DMM.

    3. Visualization

    ome DMMs will returned digitized values over the communication ports, such as a LAN, USB, or GPIB, enabling the user to do post analysis on a separate platform like Excel. On a crowded bench, it’s critical to have a DMM that stands out and displays its measurements in a clear and easy to read manner.

    4. Secondary Measurements

    Traditionally, DMMs have been used primarily to take a single measurement. In some cases, however, we want the ability to see more than one type of reading.

    5. Simple DC Power Measurements

    Power measurements are critical in many test applications. For those without a power meter, the DMM has traditionally been the instrument of choice to make such measurements. A true power measurement requires both voltage and current to be measured simultaneously, since power is voltage multiplied by current.

    While most DMMs can measure both voltage and current, they typically can’t measure both simultaneously. However, by using a few clever techniques, we can get around this issue and get a power measurement from a DMM. One such technique uses the math function.

    The Keysight Truevolt DMM has a special feature to obtain simultaneous voltage and current readings.

    6. Low-Current and Dynamic-Current Measurements

    You need to be aware of the level of current-measurement accuracy needed for your measurement applications.

    7. Measuring Difficult AC Signals

    Usually, ac voltage signals are depicted in textbooks as perfect sinusoidal waveforms. In the real world, though, ac voltage signals and currents are far from perfect. They come in widely varying shapes and values. Digitizing a small portion of an AC waveform allows you to see a few short cycles. If you’re interested in RMS amplitude or frequency measurement over a long period of cycles, you will need to make ac measurements.

    8. Temperature Variations and Auto Calibration

    If you look at a DMM datasheet, you will normally find accuracy specifications change from the time of calibration (Fig. 4). The accuracy worsens as more time elapses from the time of calibration.

    9. Triggering

    Triggers allow you to start measurements based on the detection of a trigger source. Trigger sources include continuous, external triggers such as BNC or BUS; level triggers, based on the signal crossing a certain threshold; or exhibiting triggers, which have a positive/negative slope. In most advanced DMMs, you can program a trigger delay and capture multiple sample periods surrounding a trigger event.

    10. 4-Wire Measurement

    Generally, there’s resistance in the input leads of a DMM. This resistance causes a voltage drop and yields inaccuracies in measurements. The solution to this voltage-drop problem is 4-wire sensing. Perform your measurements right at the device under test, hence bypassing the voltage drop introduced by the input leads.

    Reply
  5. Tomi Engdahl says:

    The DT830 multimeter, then. It may be a heap of junk, but it’s an astonishingly good heap of junk. I for one, salute it.

    https://hackaday.com/2020/09/24/in-praise-of-the-dt830-the-phenomenal-instrument-you-probably-dont-recognise-for-what-it-is/

    Reply
  6. Tomi Engdahl says:

    Ode To An AVO 8 Multimeter
    https://hackaday.com/2020/10/27/ode-to-an-avo-8-multimeter/

    It’s a treasure from my youth, that most venerable of British test equipment: the AVO 8. This was the ubiquitous multimeter to be found in all manner of electrical and electronic workshops across most of the 20th century, and remains to this day one of the highest quality examples of its type.

    It’s a relatively huge Bakelite box about 190mm x 170mm x 100mm in size, and it is instantly recognisable by its dual rotary selector switches and the window for viewing the needle, which forms a characteristic circular arc kidney shape.

    The earliest ancestors of my meter appeared in the 1920s, and the first model 8 in the early 1950s.

    A Very Different Approach To A Meter

    To fully appreciate the AVO 8, it’s time for a teardown, for a glimpse both at how a very high quality analogue multimeter is built as well as how such things were designed at the dawn of the Jet Age. Dismantling it is very easy, a couple of screws allow removal of the battery compartment cover on the side above the meter, and six screws in the sides of the meter undo to allow the Bakelite tub to be eased away from the front face.

    It’s first worth a quick peek in the battery compartment, where there would be two batteries for the various resistance ranges. One is the familiar D cell while the other is a BLR121, a curious 15 V pile of cells of the type once used in devices such as hearing aids and camera flashes. This cell is still available from specialist suppliers for AVO owners, but another option has been to incorporate a little switching regulator to generate the required potential.

    Turning attention to the meter itself, and immediately we are in a world of electronics from another era. The meter movement has a full-scale deflection of 50 μA and us a significantly substantial affair whose magnet alone is larger than many modern panel meters in their entirety. The parallax mirror is a substantial piece of glass mirror fixed to the back of the scale — a nice touch.

    The rotaty switches don’t use the tag-and-wiper method you might expect, instead relying on a set of springy copper finger contacts of the type you might see in older relays, that are pushed down by cams on the rear of the knob mechanism.

    It’s clear then that the AVO remains an extremely high quality instrument, and is still a useful and accurate multimeter well into its sixth decade. I feel guilty then that I’ve neglected it in favour of a digital meter that cost an order of magnitude less. So why has it remained on the shelf then? An obvious answer might be that as an analogue meter its 20 kΩ/V sensitivity can’t match the high impedance of its digital rival, but that’s probably not the real reason. It’s seductive to carry a feather-light handheld unit rather than one the size of a medium-sized building block. That’s the real benefit of modernity: miniaturisation. I’ll try to use the AVO more on the bench because it’s a fantastic instrument. But will it regain its place as my main meter? Probably not. After all sometimes it’s better to stay in 2020 rather than 1950.

    Reply
  7. Tomi Engdahl says:

    https://www.eevblog.com/forum/testgear/dual-impedance-multimeter-recommendations/

    I need a meter with LoZ impedance, I have the 289, but I need another, my options are the Fluke 117 or GreenLee DM-830A. I know the greenlee is a brymen. I have another amprobe and keysigth meters, but the performance is not sorprendent like the my Flukes. For example my U1282A, the bar graph when I work with Ohms is more slow than my Flukes, the bar graph performance in the u1282a only detects clicks on 40 Hz update mode. My Fluke 87V even on hi-res mode the bar graph is fast. Really brymen meters are fast? the money difference between Fluke 117 and DM-830A is not important, but DM-830A it has a interesting LoZ mode, for example, the LoZ for Fluke is 3 kOhms, for keysight is 2 kOhms up to 600 V for both, the brymen change the input impedance from 3 kOhms to 460 kOhms for 1000 V, sounds good but, is functional? the brymen responce is really more fast to Fluke 117? Regards.

    Reply

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