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Automotive/Voltmeter vs Multimeter


Hi Ernie,

I bought an analog voltmeter for $50 to measure battery life, load on battery, and charging system.  But then I thought, a multimeter does the exact same thing, and it's digital for only $10.  I am thinking of returning the voltmeter.  Do I have any need for it?  

Note:  I am an amateur at auto mechanics and electronics.  I just want to diagnose [and maybe replace my own alternator, starter] and battery, instead of having to go to a mechanic.

Thank you,


While a MultiMeter of any type, whether digital or analog, offers the flexibility of measuring not only system voltage, but also current (with care*, up to its specified limit, ten amperes (10A) for most general-purpose instruments), true-RMS levels of complex V and I waveforms for the higher-spec versions of these, along with frequency, duty-cycle and, perhaps, TTL logic levels.  MultiMeters also measure resistance up to 10 MegOhms, and often include built-in test oscillators so as to derive Capacitance and Inductance values as well.  This does make a good multimeter a good practical choice, if your greater use would be general electrical and/or electronics measurement.  NOTE: if you are going to use any meter for *(from above) electrical power circuits in the home, do make sure that the meter - of whatever type - is suitable for at least category III, 600V; this will be noted via text adjacent to the V and COM terminals.

Having said that, there is much to be said for the use of a purpose-built and built-in voltmeter for automotive electrical systems.  This type of voltmeter, often sold as a "battery-condition" meter can provide very good insights not only to battery condition but to that of the alternator.  These meters differ from the other common type of "analog" (meaning moving-coil d'Arsonval movement "needle") meters by virtue of their using a thermal bimetallic movement instead.  This is slower to process changing signals than is a magnetic moving-coil meter and therefore is better able to enable one to see "trends of change" of voltage rather than instantaneous absolute voltage.  Effectively, this is an RMS meter, in that it indicates the "effective" or heating value of a voltage, and thereby evens out short-term peak and dip events.  (In fact, such a voltmeter can just as readily measure AC - up to 16V or so, in this case - with no need for a rectifier, and would give correct RMS readings for even distorted waveforms to a point, crest factor limited - which, according to Fourier definition and math, can be broken down to complex sums of several simple sine waves.)

So, if your fifty dollar V-meter IS a panel-mount battery-condition meter, then why not keep it and put it to work in your car?  This is one instrument that I always add to my vehicles.

As to the ten-buck DMM, buy it anyway for your ongoing pursuits - this is the full-price cost of only three Grande Quad Long no-room Americanos from StarBucks anyway!

Best regards ... EGK  


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Ernest (Ernie) Kenward


The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!


A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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